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E-ISSN 1471-0676 • Platinum Metals Rev., 2013, 57, (1), 1•

Editorial Team: Jonathan Butler (Publications Manager); Sara Coles (Assistant Editor); Ming Chung (Editorial Assistant);Keith White (Principal Information Scientist)

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Platinum Metals ReviewA quarterly journal of research on the platinum group metals

and developments in their application in industryhttp://www.platinummetalsreview.com/

JANUARY 2013 VOL. 57 NO. 1

Contents Highly Effi cient Phosphorescent Materials Based on Platinum Complexes 2 and Their Application in Organic Light-Emitting Devices (OLEDs) By Xiaolong Yang, Chunliang Yao and Guijiang Zhou

XXV International Conference on Organometallic Chemistry 17 A conference review by M. Fátima C. Guedes da Silva and Armando J. L. Pombeiro

Photocatalytic Activity of Doped and Undoped Titanium Dioxide 32 Nanoparticles Synthesised by Flame Spray Pyrolysis By Irene E. Paulauskas, Deena R. Modeshia, Tarek T. Ali, Elsayed H. El-Mossalamy, Abdullah Y. Obaid, Sulaiman N. Basahel, Ahmed A. Al-Ghamdi and Felicity K. Sartain

“Design and Applications of Single-Site Hetergeneous Catalysts: 44

Contributions to Green Chemistry, Clean Technology and Sustainability” A book review by Richard Wells and Alan McCue

IX International Conference on Mechanisms of Catalytic Reactions 46 A conference review by Fiona-Mairéad McKenna

“PEM Fuel Cells with Bio-Ethanol Processor Systems: A Multidisciplinary 52 Study of Modelling, Simulation, Fault Diagnosis and Advanced Control” A book review by Laura Calvillo

Phase Diagram of the Iridium-Rhenium System 57 By Kirill V. Yusenko

“Fuel Cell Science and Engineering: Materials, Processes, 66 Systems and Technology” A book review by Brant Peppley

“Platinum 2012 Interim Review” 70

Publications in Brief 72

Abstracts 76

Patents 79

Final Analysis: Catalysis “After the Goldrush” 82 By Stan Golunski

•Platinum Metals Rev., 2013, 57, (1), 2–16•


Highly Effi cient Phosphorescent Materials Based on Platinum Complexes and Their Application in Organic Light-Emitting Devices (OLEDs)

http://dx.doi.org/10.1595/147106713X659019 http://www.platinummetalsreview.com/

By Xiaolong Yang, Chunliang Yao and Guijiang Zhou*

MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and Department of Chemistry, Faculty of Science, Xi’an Jiaotong University, Xi’an 710049, P.R. China

*Email: [email protected]

Although numerous materials can be utilised as emitters

in electroluminescent devices, platinum complexes

bearing organic ligands are among the most promising

for use as highly effi cient phosphorescent materials in

which the singlet and triplet states can be simultaneously

harvested for emission. This article aims to give an

overview of recent progress in Pt phosphors featuring

ingeniously designed ligands and to summarise their

impressive performances when incorporated into

organic light-emitting devices (OLEDs). Such materials

show great promise for applications such as fl at screen

displays and low-energy solid-state lighting.

1. IntroductionOLEDs have drawn much attention in the past two

decades for their applications in new generation

displays with unique advantages, such as low cost, high

contrast, good colour range, wide viewing angle and

fl exibility (1–5). In addition, OLEDs emitting white light

(white OLEDs or WOLEDs) are promising candidates

for future energy-saving solid-state light sources due

to their low driving voltage, high brightness and high

effi ciency (6–10). Emissive materials are the most

critical functional component of OLEDs and have

therefore been the subject of considerable research

activity. However, traditional fl uorescent (singlet)

emitters employ only singlet excitons, which make up

only ca. 25% of all generated excitons, and leave the

remaining triplet excitons unharnessed. This results

in low electroluminescence (EL) effi ciency which

has restricted the practical application of OLEDs,

especially as solid-state lighting sources where high

effi ciency is a prerequisite.

This situation changed with the discovery of

phosphorescent (triplet) emitters. This type of emitter

is generally constructed by chelating transition metal

ions with organic ligands. The introduction of heavier

transition metal ions effectively triggers phosphorescent

emission by spin–orbit coupling (11). Iridium(III),

Platinum complexes show promise for fl at screens and energy effi cient lighting

http://dx.doi.org/10.1595/147106713X659019 •Platinum Metals Rev., 2013, 57, (1)•


platinum(II), osmium(II) and ruthenium(II) ions are

highly effective for this purpose. Complexes of these

metals can use both the singlet and triplet excitons

when incorporated into OLEDs, which can achieve a

maximum internal quantum effi ciency (IQE) of 100%

(12). Metallated phosphors have since been extensively

investigated for use in WOLEDs as a practical avenue

towards solid-state lighting sources.

Pt-based phosphors appear to have the highest

potential for EL applications due to their higher

triplet quantum yield (ФP), relatively short triplet

state lifetime (P), and tunable emission colour. Pt

phosphors have been developed with both diverse

structures and versatile properties. This review will

highlight and critically discuss recent advances in

Pt-based complexes as highly effi cient phosphors for

high performance OLEDs. Based on their structural

features, these phosphors are classifi ed into three

main categories for discussion according to the

dentation number of the main ligands chelated with

the Pt centres:

(a) Tetradentate ligands;

(b) Tridentate ligands;

(c) Bidentate ligands.

2. Platinum Phosphors with Tetradentate LigandsThis type of triplet emitter mainly includes Pt(II)

porphyrin and Schiff base complexes. The pioneering

phosphor of this type was Pt(II) octaethylporphine

(PtOEP) (Figure 1) which can show a peak IQE of

23% and an external quantum effi ciency (EQE) of

4% with pure red EL at 650 nm. The quantum and

power effi ciencies are at least one order of magnitude

higher than those of europium complexes (13). Due

to the intrinsically long triplet lifetime of Pt phosphors

with tetradentate ligands, bulky substituents can be

introduced to block triplet–triplet (T–T) annihilation

and enhance their EL effi ciencies, especially at higher

current densities. Even the near-infrared emitters Pt

tetraphenyltetrabenzoporphyrin (Pt-TPTBP) and Pt

tetraaryltetrabenzoporphyrins (Pt-Ar4TBP) (Figure 1) can achieve high EQE values of 8.0% and 9.2% at 773 nm

(14), respectively.

Che and coworkers have prepared many

tetradentate Pt(II) Schiff base phosphors and tested

their EL potentials in OLEDs as well as investigating

their structure–property relationships (15–17). The

fi rst such complex, PtSB-1 (Figure 2), showed

promising EL effi ciencies with a peak EQE of

11.0% and a current effi ciency (CE) of 30.0 cd A–1

(15). OLEDs based on PtSB-2 (Figure 2) showed

a maximum EQE of 9.4% and a lifetime of more

than 20,000 h at a brightness of 100 cd m–2 (16).

Bis(pyrrole)-diimine Pt(II) complexes may also be

good candidates for highly effi cient OLEDs (17).

A device using PtSB-3 (Figure 2) as emitter gave

a maximum brightness of 11,100 cd m–2, an EQE

of 6.5%, a CE of 9.0 cd A–1, and a power effi ciency

(PE) of 4.0 lm W–1. These promising results indicate

that such tetradentate Pt(II) complexes may be

competitive candidates for OLED applications.

PtOEP Pt-TPTBP Pt-Ar4TBP

Pt NN

N

NPt

N

N

N

NPt

N

NN

N

Fig. 1. Chemical structures of some Pt-porphyrin phosphors



3. Platinum Phosphors with Tridentate LigandsPt(II) phosphors with tridentate ligands typically

bear rigid main ligands, including N^N^C-, N^C^N-,

N^N^N- and C^N^C-coordinating ligands, to form

cyclometalated complexes. These ligands are thought

to improve the rigidity of the corresponding Pt(II)

complexes by suppressing the D2d distortion to induce

higher ФP (18), hence promoting the performance of

electrophosphorescent devices.

3.1 Platinum Phosphors with N^N C-coordinating LigandsMuch work on cyclometalated Pt(II) complexes

based on N^N^C-coordinating ligands (PtNNC-1 to

PtNNC-9, Figure 3) and their emitting characteristics

have been reported by Che et al. (19, 20). In solution,

tridentate Pt(II) complexes bearing -alkynyl auxiliary

ligands can emit a variety of colours from 550 nm to

630 nm, induced by ligands with different steric and

electronic properties. Although their EL performance

is poor, these complexes have provided valuable

information on tuning the emission colour of this type

of phosphor.

Importantly, their performance was markedly

improved by extending the π-conjugation of the

ligands, for example PtNNCCl-1 (Figure 4) had a

ФP of 0.68 and a maximum CE of 20.2 cd A–1 (21). The

performance of this device was superior to those based

on tetradentate Pt(II) Schiff base phosphors (15, 16).

Extending the π-conjugation of the N^N^C ligands

with a fl uorene unit has been shown to play a critical

role in increasing phosphorescent emission and EL

effi ciency, in devices based on complexes PtNNCCl-2

to PtNNCCl-6 (22). The ФP for PtNNCCl-2 was 0.07

and that for PtNNCCl-3 was 0.16, while PtNNCCl-4

and PtNNCCl-5 exhibited ФP values of 0.35 and 0.73,

respectively. Owing to its high ФP, PtNNCCl-5 was

used in a vacuum deposition fabricated device which

exhibited very attractive EL effi ciencies with an EQE

of 5.5%, a CE of 14.7 cd A–1 and a PE of 9.2 lm W–1. The

moderate EL performance of PtNNCCl-6 is thought

to be due to the method of solution-processed device

fabrication.

3.2 Platinum Phosphors with N C N-Coordinating LigandsAs noted earlier, higher rigidity of the molecular

skeleton generally leads to higher ФP.. J. A. G. Williams

et al. reported that the platinum–carbon bond lengths

in Pt(N^C^N) complexes are around 1.90 Å, about 0.14 Å

shorter than those in typical Pt(N^N^C) complexes

(23). Furthermore, the shorter Pt–C bond length is

expected to deactivate the d-d states by raising their

energy, and hence lead to superior performance. This

can be seen in a new series of Pt( N^C^N) complexes

bearing various aryl substituents (Figure 5) (24). All

of the new phosphors display ФP values from 0.46 to

0.65 with emission maxima from 481 nm to 588 nm.

Additionally, the introduction of 4-(dimethylamino)-

phenyl to N^C^N ligands can suppress the self-

quenching and aggregation/excimer formation which

would otherwise hamper the EL effi ciencies. OLEDs

employing complexes PtL 1Cl to PtL9Cl as emitters (25)

can achieve maximum EQE values from 4 to 16% and

CE values from 15 to 40 cd A–1, accompanying extremely

low EL effi ciency roll-off with increased driving voltage.

The EL performance of these phosphors can also

be optimised by changing the auxiliary ligand and

the host materials in devices. Replacing the ancillary

chloride (–Cl) ligand in PtL3Cl with a phenoxy (–OPh)

group gives PtL3OPh (26), which can provide very

admirable green-emitting OLEDs with a maximum

EQE of 16.5% and a CE of 67.1 cd A–1. By adopting a

two-host system to optimise the energy levels between

charge-transport layers and confi ning the emissive

zone, the EL effi ciencies for PtL10Cl-based devices

have been almost doubled with respect to those of

their single-host counterparts, to give an EQE of 11.5%,

a CE of 38.9 cd A–1 and a PE of 27.2 lm W–1 (27).

Jabbour et al. constructed a highly effi cient blue

phosphor PtL11Cl (28) with a maximum ФP of 0.8 in

PtSB-1 PtSB-2 PtSB-3

NNPt

O O

NNPt

O O

PtN N

N N

Fig. 2. Chemical structures of some Pt(II) Schiff base phosphors



NN

Pt

NN

PtN

NPt

NN

Pt

NN

Pt

NN

Pt

NN

PtN

NPt

NO2 OCH3

COOCH2CH3

COOCH2CH3

NN

Pt

F

FF

F

FF

FF

F

FF

FF

F

F

Blue-shift

Blue-shift

Red-shift

Red-shift

PtNNC-2max = 582 nm

Red-shift

PtNNC-5max = 622 nm

max = 630 nm

PtNNC-4

PtNNC-1max = 600 nm

max = 560 nm

PtNNC-3

PtNNC-9max = 571 nm

Blue-shift

PtNNC-8 max = 550 nm PtNNC-6 max = 560 nm max = 593 nmPtNNC-7

Fig. 3. Chemical structures of typical Pt(II) complexes with N^N C-coordinating ligands and their emission maximum in CH2Cl2 solution at 298 K

degassed dichloromethane (CH2Cl2) (29), which was

ascribed to both its rigid triplet state confi guration

and very high ligand-fi eld strength giving a strong

destabilisation to the metal-centred d-d excited states.

A deep-blue device based on PtL11Cl doped in a

co-host gave a maximum EQE of 16% and a PE of

20 lm W–1. A WOLED based on 8 wt% PtL11Cl doped

in 1,3-bis(N-carbazolyl)benzene (mCP) exhibited

a maximum EQE of 9.3%, a PE of 8.2 lm W–1 and

Commission Internationale de l’Éclairage (CIE)

coordinates of (0.33, 0.35) at 1300 cd m–2, very close to

the pure white point at (0.33, 0.33).

Another highly effi cient phosphor PtL12Cl (Figure 5) with a ФP of 0.87 was incorporated into

OLEDs at doping levels of 10, 15, 20 and 25 wt%,

respectively. By varying the doping level, the EL colour

of the devices could be tuned from bluish-green to red

with very high EQE values up to 18.3% (30). It is worth

mentioning that the electron-donating groups attached

to the lateral pyridyl rings of the Pt complexes resulted



NN

Pt

Cl

C6H13

C6H13

NN Pt

Cl

C6H13

C6H13

R

NN Pt

Cl

C6H13

C6H13N

N Pt

Cl

PtNNCCl-1 PtNNCCl-2 PtNNCCl-3

PtNNCCl-4 R = H PtNNCCl-5 R = PhPtNNCCl-6 R = 3,5-tBuPh

Fig. 4. Chemical structures of phosphors PtNNCCl-1 to PtNNCCl-6

Fig. 5. Chemical structures of high performance Pt(N C N) phosphors

PtN N

R

Cl

PtN N

Cl

N

PtN N

Cl

N

C4H9

N

C4H9

PtL9Cl PtL10Cl

PtN N

O

PtL3OPh

PtN N

Cl

FF

PtL11Cl

PtN N

Cl

FF

PtL12Cl PtL13Cl

PtN N

Cl

FF

H3CO OCH3

PtL1Cl R = HPtL2Cl R = C(O)OMePtL3Cl R = MePtL4Cl R = 2-pyridylPtL5Cl R = mesitylPtL6Cl R = biphenylylPtL7Cl R = tolylPtL8Cl R = thienyl

in a blue-shift in the monomer emission, as well as

excimer emission resulting from the interactions

between emitter molecules (29). Accordingly, PtL13Cl (31) showed a blue-shift emission compared with

that of PtL12Cl due to the stronger electron-donating

ability of the methoxy group (–OCH3) compared

to the methyl group (–CH3). By tuning the doping

concentration from 5 wt% to 35 wt%, OLEDs based on

PtL13Cl could be made to emit nearly any colour from

blue to yellowish red. The dependence of emission



colour on doping concentration offers a very simple

and practical way to regulate OLED emission colour

by adjusting the contributions of monomer and

excimer emission.

3.3 Platinum Phosphors with N^N^N-Coordinating LigandsChen et al. introduced a trifl uoromethyl-pyrazolyl

group to 2,2-bipyridine to form a neutral tridentate

cyclometalated ligand, 6-(5-trifl uoromethyl-pyrazol-3-

yl)-2,2-bipyridine, and investigated the photophysical

properties of the resulting complexes (Figure 6) (32).

These complexes emit phosphorescence between

524 nm for PtNNN-1 and 604 nm for PtNNN-2. The

bathochromic effect in emission may lie in the stronger

donor ability of acetamide and the larger π-conjugation

involving the nitrogen and the carbonyl group of

acetamide in PtNNN-2. An optimised device doped

with 28 wt% PtNNN-1 exhibited a maximum EQE

of 8.5%, corresponding to a CE of 18.5 cd A–1 and a

maximum brightness of 47,543 cd m–2 at 18.5 V.

Cola et al. also reported several Pt(N^N^N)-type

complexes displaying ФP values of up to 0.73 in

deaerated chloroform solution (33), which are among

the highest found for tridentate chelates (21, 22, 27,

34). A multilayer vapour deposited device doped with

6% PtNNN-3 (Figure 6) generated a green emission

peak at 510 nm with a second peak at 544 nm and

gave a maximum CE of 15.2 cd A–1 and a PE of 6.8 lm W–1,

which is comparable with the performance of devices

based on the well-established green emitter, Ir(ppy)3,

in a similar architecture.

3.4 C N C-Coordinating Ligands Based Platinum PhosphorsThough several Pt(II) complexes with C^N^C type

ligands were reported in 2002 (35), they drew little

attention due to their poor emission (35, 36). Recently,

Kui et al. reported the fi rst examples of complexes

of these ligands with intense phosphorescence in

solution at room temperature (Figure 7) (37). By

functionalising with carbazole, fl uorene, or thiophene

heterocyclic unit(s) at the periphery, they can show

ФP values up to 0.26 in solution at room temperature.

This emission performance has been ascribed to

both the -donating ability of the CNR ancillary

Pt N

Cl

N

NN

CF3

PtNNN-1 PtNNN-2 PtNNN-3

PtN

C5H11

N NNN N

N

N

Pt

N

NNCF3

NHO

N

PtCNC-1 PtCNC-2

Pt

C

N

C6H13C6H13NS

Pt

C

NS

N

Fig. 6. Chemical structures of PtNNN-1 to PtNNN-3

Fig. 7. Chemical structures of PtCNC-1 and PtCNC-2



ligand and the rigidity of the triplet state due to the

carbazole, fl uorene or thiophene heterocyclic units

in the main ligand. Red-emitting OLEDs based on this

ligand system can give very decent EL performance.

For example, a device based on PtCNC-1 displayed a

maximum EQE of 12%, a PE of 10.9 lm W–1 and a CE of

13.9 cd A–1, while a device doped with 6 wt% PtCNC-2

achieved a maximum EQE, PE and CE of 12.6%,

10.5 lm W–1 and 13.4 cd A–1, respectively.

4. Platinum Phosphors with Bidentate Ligands4.1 Conventional (N C)Pt(O^O) PhosphorsComplexes with one N^C main ligand (2-phenylpyridine-

type or ppy-type) and one ancillary -diketonato

ligand (acetyl acetone or its derivatives) represent the

fi rst and most developed type of EL phosphors, with

good emission and tunable colour.

J. Brooks et al. reported a series of this type of

phosphor, Ptppy-1 to Ptppy-8 (Figure 8), which

show intense phosphorescence at room temperature

(38). They also show distinct emission colour tuning

properties. Introducing electron-withdrawing groups

to the phenyl moiety and electron-donating groups

to the pyridyl ring in the ppy ligand can induce a

blue-shift in the emission maxima (max = 486 nm

for Ptppy-1, max = 484 nm for Ptppy-3 and max =

466 nm for Ptppy-2, max = 456 nm for Ptppy-6 and

max = 440 nm for Ptppy-7), while electron-donating

groups on the phenyl ring of the ligand will cause a

red-shift (max = 525 nm for Ptppy-4 and max = 480 nm

for Ptppy-5). Theoretical calculations indicate

that this colour tuning behaviour can be explained

in terms of the highest occupied molecular orbitals

(HOMOs), contributed mainly by the π orbitals of the

phenyl ring and the dπ orbital of the Pt centre, and

NPt

O

O

Ptppy-1

NPt

O

O

F

F

Ptppy-2

NPt

O

O

F

F

Ptppy-3

NPt

O

O

O

Ptppy-4 Ptppy-5

NPt

O

O

O

NPt

O

O

F

F

Ptppy-6

Ptppy-8

NPt

O

OF

F

Ptppy-7

NPt

O

O

F

F

N

IrN

N

N

F

FF

F

OO

FIrpic

Fig. 8. Chemical structures of Ptppy-1 to Ptppy-8 plus FIrpic



the lowest unoccupied molecular orbitals (LUMOs),

located mainly on the orbitals of the pyridyl ring in

the ligands.

The excimer emission in the orange or red

region caused by interaction among molecules

means that blue-emitting phosphors can be used to

fabricate simple WOLEDs by a blue-orange ‘colour

complementary’ strategy. Co-doping Ptppy-2 and

FIrpic (Figure 8) in a single layer allows the blue

monomer emission from FIrpic and the orange

excimer emission from Ptppy-2 to be combined,

providing white light for simple WOLEDs with a single

emissive layer (EML) (39). Based on the same strategy,

the single phosphor Ptppy-8 can also be used to

create simple WOLEDs with just one EML (40).

Importantly, the performance of these simple

WOLEDs can easily be improved by inserting an

electron blocking layer (EBL), selecting the proper

host materials, and optimising the energy levels of the

functional layers, thus balancing the carrier injection in

the device. In single EML WOLEDs with Ptppy-2 as the

emitter, the EL efficiencies could be improved to a

peak EQE of 6.4%, a CE of 17.0 cd A–1 and a PE of

12.2 lm W–1 by inserting an Irppz EBL. The host 2,6-bis(N-

carbazolyl)pyridine (mCPy) could guarantee a more

effi cient energy transfer to Ptppy-2 than conventional

mCP. Simple WOLEDs with Ptppy-2 doped into mCPy

could thereby furnish better device effi ciencies with

an EQE of 6.9% and a CE of 15.7 cd A–1 at 500 cd m–2.

Taking poly(3,4-ethylenedioxythiophene):poly(4-

styrenesulfonate) (PEDOT:PSS) as the hole injecting

layer (HIL) and poly(N-vinylcarbazole) (PVK) as the

hole transport layer (HTL) as well as the EBL, the

effi ciencies of simple WOLEDs could be maximised

to an EQE of 18%, a PE of 29 lm W–1 and a CE of

42.5 cd A–1 (41), corresponding to an IQE of nearly

100% (42). These dramatic enhancements may be

attributed to the smoother interface of PEDOT:PSS/

PVK compared to that of PEDOT:indium tin oxide

(ITO)/PVK, resulting in a smaller interfacial surface

area and lower leakage current. Furthermore, ITO/

PVK has an injection barrier 0.6 eV larger than that of

ITO/N,N-di-[(1-naphthyl)-N,N-diphenyl]-1,1-biphenyl)-

4,4-diamine (NPD) (the HOMOs for PVK and NPD are

5.8 eV and 5.2 eV, respectively) and PVK has a much

lower hole mobility than NPD, which can effectively

reduce the number of holes injecting to the emissive

layer, leading to a more balanced ratio of holes and

electrons.

Some phosphors with substituted -diketonato

ligands (Ptppy-9 and Ptppy-10) (Figure 9) were

also obtained (43). Although the substituents can

exert only limited electronic effects on the complex

cores, they can evidently infl uence the molecular

packing in the crystals and the thin fi lms to facilitate

the fabrication of simple non-doped devices. The

attractive EL performance of non-doped devices

based on Ptppy-10, with a peak EQE of 9.76%, a CE of

28.1 cd A–1 and a PE of 9.91 lm W–1 at 500 cd m–2 indicates

the great potential of these phosphors for simplifying

device fabrication, since traditional phosphorescent

OLEDs generally possess doped EMLs which are much

more complicated to construct.

Ptppy-2 can be attached to a random terpolymer

backbone containing hole-transport (HT) and

electron-transport (ET) moieties, leading to a range

of phosphorescent terpolymers (44) ( Figure 10).

The polymeric phosphor Ptppy-P was employed

to prepare a simple solution-processed OLED, with

a maximum EQE of 4.6% and CIE coordinates of

(0.33, 0.50). Ptppy-2 has also been attached to a

polyhedral oligomeric silsesquioxane (POSS) core

(45) (Figure 10). The carbazole moieties provided

effi cient HT character as well as diluting the

concentration of the Pt complex bonded to the POSS,

thus controlling the emission contributions from

the monomer and excimer states. The maximum

EQE was 8.4% for a Ptppy-POSS based solution-

processed WOLED. Although its CIE coordinates

of (0.46, 0.44) deviate slightly from the ideal white

point at (0.33, 0.33), the EL spectrum of the device

was voltage-independent, indicating good colour

stability.

NPt

O

OR

F

F

Ptppy-9

Ptppy-10

R =

NR =

Fig. 9. Chemical structures of Ptppy-9 and Ptppy-10



4.2 Functionalised (N C)Pt(O^O) PhosphorsBesides the Pt phosphors described above,

functionalised analogues have also been developed

to address some critical issues in OLEDs, including

carrier injection/transport, emission colour tuning and

T–T annihilation.

A series of Pt phosphors functionalised with

main group elements have been designed and

synthesised (Figure 11) (46–49). Some of these

might represent the highest ФP values ever reported

for Pt phosphors, at 0.93 for Pt-PO and 0.95 for Pt-SO2. The diphenylamino group (NPh2) has been

shown to add HI/HT functionality to Pt-N, while

dimesitylboron B(Mes)2, diphenylphosphoryl (POPh2)

and phenylsulfonyl (SO2Ph) moieties can provide EI/ET

functionality to Pt-B, Pt-PO and Pt-SO2, respectively

(48). It is well known that carrier injection/transport

are very important to the EL process. Hence, Pt-B, Pt-N, Pt-PO and Pt-SO2 exhibit much better EL effi ciencies

(with CE values of 30.00 cd A–1, 29.74 cd A–1, 22.06 cd

A–1 and 19.59 cd A–1, respectively) than do other

congeners (8.47 cd A–1 for Pt-Si, 8.49 cd A–1 for Pt-Ge,

11.42 cd A–1 for Pt-O and 16.77 cd A–1 for Pt-S, for

example), indicating the great potential of such

functionalisation for enhancing the EL performance

of Pt phosphors.

Inspired by the success of Pt-B, other effi cient

Pt phosphors bearing B(Mes)2 were also prepared

(Figure 11). Pt-pyB can show outstanding EL

performance with an EQE of 20.9%, a CE of 64.8 cd A–1

and a PE of 79.3 lm W–1 (50). This complex also shows

comparable HI/HT and EI/ET properties to those

Ptppy-POSS

n om

N

O O

O

O

PtN

F

F

NN

N

Ptppy-P

Molar ratiom:n:o10:1:10

R = –CH2(CH2)5O

N

N

NPt

O

O

F

FSi

OO

RSi

Si

Si

SiSi

Si

SiSi Si

Si

Si

Si

Si

Si Si

O

O

OO

O

OO

O

O

OO

O

R

R

R

RR

RO

OO

O

O O

Fig. 10. Chemical structures of Ptppy-P and Ptppy-POSS



of the analogous Pt-NO and Pt-NB, and has decent

effi ciencies with an EQE of 10.6%, a CE of 33.2 cd A–1

and a PE of 34.8 lm W–1 (51).

Additionally, these phosphors can exhibit unique

colour tuning behaviours. Pt-B (em = 542 nm), Pt-PO (em = 500 nm) and Pt-SO2 (em = 503 nm) bearing

electron-withdrawing main group moieties on the

phenyl ring of their ppy ligands show a bathochromic

(red-shift) effect in their emission maxima with

respect to that of their parent complex Ptppy-1 (em = 486 nm). These results are in confl ict with

traditional colour tuning theory, which predicts a

PtO

O

N

N

Pt-N

PtO

O

N

O

Pt-O

PtO

O

N

Ge

Pt-Ge

PtO

O

N

Si

Pt-Si

PtO

O

N

B

Pt-B

PtO

O

N

S

Pt-S

PtO

O

N

SO O

Pt-SO2

PtO

O

N

P O

Pt-PO

PtO

O

N

B

Pt-pyB

Pt-NB

Pt-NO

PtO

ON

N

NN

OPt

O

O

N

N

B

Fig. 11. Chemical structures of some functionalised Pt phosphors



hypsochromic (blue-shift) effect in the emission

wavelength when electron-withdrawing moieties are

introduced to the phenyl ring of the ppy ligands (38).

Time-dependent density functional theory (TD-DFT)

calculations show that the electrons in the metal-

to-ligand charge transfer (MLCT) process mainly

go to the main group moieties B(Mes)2, POPh2 and

SO2Ph in Pt-B, Pt-PO and Pt-SO2 rather than to the

pyridyl ring in the ligand as in their conventional

counterparts (38). This means that the electron-

withdrawing main group moieties have changed

the direction of the MLCT process compared to the

unfunctionalised pyridyl ring complexes, an effect

which is not seen with other electron-withdrawing

groups such as F or CN which cannot host electrons.

The stronger electron-withdrawing properties of the

main group moities compared to the pyridyl ring in

the ligand allows them to stabilise the MLCT states.

The phosphorescence from triplet MLCT states in

Pt-B, Pt-PO and Pt-SO2 can therefore be expected

to show red-shift. Similar colour tuning behaviour

was also observed in fl uorenone-based Pt phosphors,

indicating the universality of this effect (52). The

importance of this new colour tuning strategy lies

in that it makes possible the design and synthesis of

long wavelength phosphors with EI/ET properties.

The high LUMO levels for Pt-Si, Pt-Ge, Pt-O and

Pt-S mean that electrons can leak into the 4,4-bis-

[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) layer,

resulting in blue emission which provides a chance

to generate white light by mixing with the green

monomeric emission and orange/red excimer

emission from the Pt phosphors. This could provide

another route towards simple WOLEDs emitting

good quality white light. Pt-Ge and Pt-O have been

employed in OLEDs with the simple confi guration

indium tin oxide/NPB /x% Pt: 4,4-bis(N-carbazolyl)-1,1-biphenyl/bathocuproine/tris(8-hydroxyquinolinato)-

aluminium/lithium fl uoride/aluminium (ITO/NPB/x%

Pt:CBP/BCP/Alq3/LiF/Al) (49). As expected, these

simple devices can emit high quality white light with

a blue component from NPB and green and orange/

red components from the monomer and excimer of

the Pt phosphor, respectively. Pt-Ge based devices can

reach an exceptionally high colour rendering index

(CRI) of up to ca. 97 at brightness > 15,000 cd m–2, a

correlated colour temperature (CCT) of 4719 K and

CIE coordinates of (0.354, 0.360) at a doping level of

10 wt%. A 6 wt% Pt-O doped WOLED produced white

light with a CRI of ca. 94, a CCT of 6606 K and a CIE

of (0.320, 0.340), perhaps the best quality white light

ever produced by WOLEDs, comparable with natural

sunlight and therefore most suitable for artifi cial

lighting applications.

Typically, Pt phosphors suffer from effi ciency roll-

off due to T–T annihilation induced by their inherent

square-planar structure geometry favouring strong

molecular interaction, as well as their relatively

long P (13, 30). This undesired T–T annihilation

has been successfully hindered by attaching bulky

triphenylamine moieties to the Pt phosphor ligands

(Figure 12) (53). Pt-F2TPA has a P of 8.2 μs, and

T–T annihilation can only occur at very high current

densities of 360 mA cm–2. Triphenylamine can also

enhance its HI/HT characteristics.

4.3 N^N-Coordinating Ligands Based Platinum PhosphorsChi et al. have synthesised a series of Pt(N^N)2

phosphors bearing N-heterocycle substituted pyrazole

ligands ( Figure 13). A device doped with 20 wt%

PtNN-1 showed a maximum brightness of 40,973 cd m–2

at 15 V, a peak EQE of 5.96%, a CE of 19.70 cd A–1 and

a PE of 6.44 lm W–1 (54). The optimal device based

on PtNN-2 achieved a maximum luminescence of

20,296 cd m–2 at 16 V, a peak EQE of 5.78%, a CE of

12.19 cd A–1 and a PE of 6.12 lm W–1 (55). Similarly to

other congeners, they also undergo self-aggregation at

high doping levels in devices.

M. A. Omary et al. reported a turquoise-blue

Pt(N^N)2 complex, PtNN-3 (Figure 13), in which the

N^N represents a pyridyltriazolate derivative (56, 57).

This complex features intense Pt…Pt intermolecular

Pt-F2TPA

N N

N

Pt

OO

Fig. 12. Chemical structure of Pt-F2TPA



interactions due to the strong polarity induced by

pyridyltriazolate as well as its square-planar geometry.

Generally, interactions among the phosphor molecules

will decrease EL effi ciency. However, EL effi ciencies

could be enhanced by increasing the doping level

of PtNN-3 and a maximum EQE of 19.7%, a PE of

44.7 lm W–1 and a CE of 62.5 cd A–1 were achieved

at a doping level of 65%. This interesting result may

be attributed to energy-level matching among the

functional layers within the devices to balance the

hole/electron ratio and confi ne the recombination

zone in the EML. Furthermore, the short lifetime of

PtNN-3 in the solid fi lm may play a critical role

in reducing T–T annihilation and thus enhancing

the device effi ciencies. These results might provide

valuable information on how to cope with the

problem of intermolecular interactions associated

with Pt phosphors.

4.4 Platinum Phosphors with C C-Coordinating LigandsCarbene-type ligands have also been employed to

prepare novel Pt phosphors. Y. Unger et al. prepared

some homoleptic Pt(II) biscarbene complexes

which were emissive in the deep blue region (58).

The complex PtCC-1 (Figure 14) gave intense

photoluminescence at 386 nm with a ФP of 0.45 under a

nitrogen atmosphere. Due to its emission energy being

in the ultraviolet (UV) region, the PtCC-1 phosphor

is less suitable for fabricating OLEDs. However, a

new series of carbene-type Pt(II) phosphors were

subsequently constructed using modifi ed structures

(59). The complex PtCC-2 ( Figure 14) had a ФP of

0.9 under a nitrogen atmosphere, qualifying it as a

triplet emitter for EL devices. A device based on PtCC-2

had a maximum brightness of 6750 cd m–2 and a peak

EQE of 6.2% at 13.2 V.

4.5 Platinum Phosphors with Bridged N C-Coordinating LigandsRecently, K. Feng et al. reported some interesting

Pt phosphors with bridged ligands (PtbNC-1 and

PtbNC-2) and their copolymers (PtbNC-P1 and

PtbNC-P2) ( Figure 15) (60). These Pt complexes

exhibit peak emissions around 525 nm with a

maximum ФP around 0.55 in degassed CH2Cl2

and their corresponding polymers display almost

identical photoluminescence spectra in PVK fi lms.

The investigation of the EL properties of these green-

lighting polymers shows that the novel phosphorescent

polymers can show a maximum brightness of ca.

1000 cd m–2 and a peak EQE of 2.5% (61).

Vezzu et al. also synthesised some Pt(N^C)2

complexes (Figure 15) emitting between 474 nm and

613 nm with ФP values ranging from 0.14 to 0.75 (62).

Doping 4% PtbNC-3 into a 2,2,2-(1,3,5-benzenetriyl)-

tris(1-phenyl-1-H-benzimidazole) (TPBI)-4,44-tris(N-

carbazolyl)triphenylamine (TCTA) co-host produced

a bright green emitting device (max = 512 nm) with a

peak EQE of 14.7% and a maximum CE of 50.0 cd A–1.

When the current density was increased to 10 mA cm–2,

the brightness rose to 3698 cd m–2 with signifi cant

effi ciency roll-off (EQE of 10.6% and CE of 37 cd A–2),

implying the occurrence of T–T annihilation in the

device.

5 Concluding RemarksPlatinum-based phosphors have unique properties

which give them great potential for electroluminescent

NPt

N

N

N

NN

CF3

F3C

PtNN-1 PtNN-2

PtNN-3

PtN

NN

N

O O

N N NNN

NN N

N N

Pt

Fig. 13. Chemical structures of PtNN-1 to PtNN-3

Fig. 14. Chemical structures of PtCC-1 and PtCC-2

N N

N

N

NN

N

N

Pt 2I–

2+

PtCC-1

O

O

O

N

N

Pt

PtCC-2



applications. Modifying the chemical structures

of their ligands has allowed advanced emitters to

be generated which have addressed many of the

critical issues in OLED research, including improved

photoluminescence and electroluminescence

effi ciencies, carrier injection/transport, novel colour

tuning strategies, overcoming the problem of T–T

annihilation, and the fabrication of simple WOLEDs

emitting good quality white light. These developments

and the associated performance enhancements may

soon allow Pt-phosphor based EL devices to begin

moving from the laboratory into the commercial

market. More and increasingly sophisticated triplet

emitters based on Pt will continue to be developed,

leading to further improvements in the fi eld.

AcknowledgementsThe authors thank all coworkers, PhD and BSc

students involved in the research. This work was

fi nancially supported by Xi’an Jiaotong University

(Tengfei Project), a Research Grant from Shaanxi

Province (No. 2009JQ2008), the National Natural

Science Foundation of China (NSFC) (No. 20902072),

the Program for New Century Excellent Talents in

University, and the Ministry of Education of China

(NECT-09-0651).

H3C OCH3

N NPt

FF

F F

F F

FF

F

PtN N

H3CO

PtbNC-1 PtbNC-2F

FF

F

PtN N

R (CH2)5

9n

O O

n

N N

N

N NPt

PtbNC-P1 R= F PtbNC-P2 R = OCH3

PtbNC-3

Fig. 15. Chemical structures of typical Pt phosphors with bridged ligands

Glossary

Term Defi nitionP triplet state lifetime

P triplet quantum yield

CCT correlated colour temperature

CE current effi ciency

CIE Commission Internationale de

l’Éclairage

CRI colour rendering index

EBL electron blocking layer

EI electron injection

EL electroluminescence

EML emissive layer

EQE external quantum effi ciency

ET electron transport

Term Defi nitionHI hole injection

HIL hole injection layer

HOMO highest occupied molecular orbital

HT hole transport

HTL hole transport layer

IQE internal quantum effi ciency

LUMO lowest unoccupied molecular orbital

MLCT metal-to-ligand charge transfer

OLED organic light-emitting diode

PE power effi ciency

T–T triplet–triplet

WOLED white organic light-emitting diode



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The AuthorsXiaolong Yang received his Bachelor’s degree in Applied Chemistry from Xi’an Jiaotong University, China, in 2010. He then joined Professor Guijiang Zhou’s group as a PhD candidate. His current scientifi c interest is focused on functionalised organometallic phosphors for electroluminescent applications.

Chunliang Yao received his Bachelor’s degree in Applied Chemistry from Xi’an Jiaotong University in 2010, and then joined Professor Guijiang Zhou’s group as a PhD candidate. His current scientifi c interest is focused on functionalised organometallic systems for electroluminescent and optical power limiting applications.

Professor Guijiang Zhou received his PhD degree from the Institute of Chemistry, Chinese Academy of Sciences (CAS) in 2003. After postdoctoral experience in Korea, Hong Kong and Spain, he joined Xi’an Jiaotong University as a Professor in 2008. His current research interests include functionalised phosphorescent organometallic materials for optical power limiting and electroluminescence.



XXV International Conference on Organometallic ChemistryVital role of platinum group metals highlighted at ‘Jubilee’ conference


Reviewed by M. Fátima C. Guedes da Silva* and Armando J. L. Pombeiro**

Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049–001 Lisbon, Portugal

Email: *[email protected]; **[email protected]

The XXV International Conference on Organometallic

Chemistry (XXV ICOMC) (1), was held for the fi rst

time in Portugal, taking place in Lisbon from 2nd to

7th September 2012. This highly successful series

of biennial conferences was launched in 1963 in

Cincinnati, USA. This was the ‘silver event’ (25th)

and the ‘golden year’ (the 50th year since the series

began) of this chain of conferences, and provided an

opportunity for a ‘Silver/Gold Jubilee’ celebration. A

celebratory book (2) will be published, and a special

celebratory medal was coined (Figure 1) featuring

on its reverse a representation of a platinum centre

interacting with a carbon−carbon double bond (the

Chatt-Dewar-Duncanson model). The medal was

received by all the invited speakers and the members

of the ICOMC International Advisory Board.

The conference was attended by 1218 delegates

from 54 countries (Figure 2). Over 1100 were from

outside Portugal, with a good quota (38%) of students.

The countries most represented were Germany (ca.

160 delegates), Japan (ca. 135 delegates, the second

largest representation), Portugal (ca. 115), Spain, UK,

France, Russia, Switzerland, Italy and Poland, in this

order. Japan, the country that will organise the next

ICOMC in 2014, was strongly represented; other more

distant countries included mainland China (ca. 40);

South Africa, Australia, USA and Canada (ca. 20 each);

Taiwan, Singapore and Hong Kong (between 10

and 20 each). The participation of China (mainland

Fig. 1. Silver/Gold Jubilee ICOMC celebratory medal



plus Taiwan) was identical to that of France at ca. 60

delegates each.

The scientifi c programme included a total of 1265

contributions of different types, i.e. 1.03 per participant.

There were 5 Plenary and 17 Keynote Lectures, 195

normal oral and 794 poster contributions, and the

programme also included, for the fi rst time in this

series of conferences, 165 Flash oral presentations (to

allow mainly young researchers to briefl y advertise

their posters) and 77 Satellite Sessions (invited

lectures) spread throughout the conference to

promote cooperation between younger and senior

researchers of various countries.

The inclusion of the Journal of Organometallic

Chemistry (JOM) symposium (11 invited Lectures)

in the programme, following a proposal by the Editor

Richard D. Adams (University of South Carolina, USA),

was also noteworthy.

The scientifi c programme covered all fi elds

of organometallic chemistry, from fundamental

to applied, and related areas of other sciences,

eliminating artifi cial boundaries and promoting

interdisciplinary collaboration (Figure 3). Catalysis

was the most represented fi eld (261 contributions),

followed by Fundamental Organometallic Chemistry

(156 contributions); Activation of Small Molecules,

C−H and C−C Bond Activation and Functionalization,

and Metal-Mediated Synthesis (each with ca. 80

contributions); Organometallic and Green Chemistry,

Bioorganometallic and Bioinorganic Chemistry,

and Organometallics Related Chemistry (ca. 75

each). They were followed by Organometallics for

Materials (ca. 65); Polynuclear and Supramolecular

Assemblies, Polymers, and Reaction Mechanisms

(ca. 50 each).

Quite a good number of contributions included

platinum group metals (pgms), and a representative

selection (which is intended to be merely illustrative

rather than comprehensive) is briefl y outlined herein,

concerning the main areas of the conference. Many

of the sections include contributions of relevance to

other areas in accordance with the interdisciplinary

nature of the conference.

CatalysisThree decades of Noyori’s 2,2-bis (diphenylphosphino)-

1,1-binaphthyl (BINAP) chemistry were reviewed

by their inventor, Ryoji Noyori (RIKEN and Nagoya

University, Japan), with emphasis on asymmetric

hydrogenation with rhodium- and ruthenium-BINAP

catalysts, nowadays practiced worldwide and

with broad application in stereoselective organic

synthesis, both in the laboratory and in industry.

160

140

120

100

80

60

40

20

0

Num

ber

of d

eleg

ates

German

yJap

an

Portu

gal

Spain

United

King

dom

Franc

e

Russi

a, Ch

ina (m

ainlan

d)Ita

ly

Switz

erlan

d

Polan

d

Sout

h Afri

ca

United

State

s

Cana

da

The N

etherl

ands

Taiw

an (C

hina),

Mex

ico

Singa

pore

Hong K

ong

Austri

a

India,

Israe

l, Sou

th Ko

rea, V

enezu

elaCh

ile

Braz

il, Hun

gary,

Swed

en

Iran,

Saud

i Arab

ia, Fi

nland

, Irela

nd

Belgi

um, K

azak

hstan

, Rom

ania,

Turke

y

New Ze

aland

, Alge

ria, G

reece

Oman, S

lovak

ia

Others

Austra

lia, C

zech

Repu

blic

Fig. 2. Distribution of delegates (numbers) from different countries, grouped by number of delegates



Ferenc Joó (University of Debrecen, Hungary)

described various hydrido-Ru complexes which form

in aqueous solutions at different pHs and hydrogen

pressures; these include a rare trans-dihydride, trans-

[RuH2(m tppms)4], and one of the very few dihydrogen

complexes ever observed in aqueous solution,

[RuH2(2-H2)(m tppms)3] (m tppms = monosulfonated

triphenylphosphine). The concentration distribution

of the hydrido-Ru(II) phosphine complexes explains

the rate and selectivity changes in aqueous biphasic

hydrogenation of ,-unsaturated aldehydes as a

function of pH.

Maurizio Peruzzini (Consiglio Nazionale delle

Ricerche (CNR), Florence, Italy) pointed out several

neutral mono- and bidentate P-N donor ligands

derived from the C-6 (‘upper rim’) functionalisation

of the hydrosoluble triazaphosphine 1,3,5-triaza-7-

phosphaadamantane (PTA), together with the analysis

of catalytic data related to the activity of Ru(II)

complexes in hydrogenation reactions under very

mild conditions (3).

Anna Trzeciak (University of Wroclaw, Poland),

seeking for alternative palladium catalysts for

the Suzuki-Miyaura reaction, presented Pd(II)

carbene complexes of the types [Pd(-IL)2Cl2] (IL =

N-substituted imidazole) and [IL]2[PdCl4], the former

with a high activity in ethylene glycol.

Lanny Liebeskind (Emory University, USA) explored

the chemoselective metal-catalysed desulfi tative

coupling of thioorganics with boronic acids (involving

carbon−sulfur bond cleavage and carbon−carbon

bond formation) at neutral pH, and its biological

signifi cance. He discussed a strategy based on a dual

thiophilic-borophilic activation for thiol ester-boronic

acid coupling under non-basic conditions, catalysed

by tetrakis(triphenylphosphine)palladium(0) in the

presence of a copper(I) carboxylate as cofactor

(Figure 4) (4).

Yong-Gui Zhou (Dalian Institute of Chemical

Physics, China) discussed three kinds of activation

Activation of Small Molecules

C–H and C–C Bond Activation and Functionalization

Metal-Mediated Synthesis

Catalysis

Organometallic and Green Chemistry

Polynuclear and Supramolecular Assemblies

Polymers

Organometallics for Materials

Bioorganometallic and Bioinorganic Chemistry

Fundamental Organometallic Chemistry

Reaction Mechanisms

Theoretical and Physical Methods

Electrochemistry

Organometallics and Related Chemistry

Others

0 50 100 150 200 250 300Number of contributions

Fig. 3. Distribution of abstracts (numbers) from each of the scientifi c areas covered by the conference, in order of appearance

Pd

R1

R2

L

L

L

L

OHR’

OH

SB

X

M Thiophilic

Borophillic

Fig. 4. Turning on transmetalation at palladium thiolates. The M-X cofactor enhances kinetics and thermodynamics (dual activation). L are ligands; R, R1 and R2 are functional groups; M is copper or a thiophilic metal; and X is a borophilic group



strategies for the successful asymmetric hydrogenation

of heteroaromatics (substrate activation, catalyst

activation and relay catalysis) indicating several

rhodium, ruthenium, iridium and palladium catalysts

which can be used for this purpose (5).

Hong Yan (Nanjing University, China) presented

several electronically unsaturated 16-electron

cobalt, rhodium, iridium, ruthenium and osmium

half-sandwich complexes containing a carborane-

1,2-dichalcogenolate ligand, their involvement in

catalysis towards alkyne trimerisatio n, and their

biological activity.

Jwu-Ting Chen (National Taiwan University)

showed that cationic methylpalladium(II) complexes

of the type [Pd(Me)(NCMe)(L)] (L = chelating

substituted pyridinyl aminates) can act as catalysts

for the formation of alternating cyclic olefi n

copolymerisation.

Dalmo Mandelli (Federal University of ABC,

Brazil) presented the Os carbonyl complex

[Os3(CO)12] as a rare example of a homogeneous

metal catalyst for the oxidation of glycerol with

H2O2 to produce dihydroxyacetone, glycolic acid

and hydroxypyruvic acid.

Pedro Góis (University of Lisbon, Portugal) described

the possibility of combining, in a cooperative manner,

metal and organic catalysts, giving a dirhodium

carboxylate system as an example.

Activation of Small MoleculesJitendra Bera (Indian Institute of Technology, Kampur)

discussed an organometallic approach towards water

activation. A naphthyridine group suitably placed on

a ligand scaffold (Figure 5) enhances the hydration

activity of a Rh(I) catalyst, and bifunctional water

activation for the catalytic hydration of organonitriles

was demonstrated (6).

Erwin Reisner (University of Cambridge, UK)

addressed the subject of bio-inspired solar water

splitting with metalloenzymes and synthetic catalysts

integrated in nanostructured materials, recalled that

direct solar fuel generation needs a fi nely tuned

combination of light absorption, charge separation

and redox catalysis, and referred to Ru-dye sensitised

titania nanoparticles modifi ed with hydrogenases as

suitable catalysts for proton reduction to molecular

hydrogen (7).

Sylviane Sabo-Etienne (University of Toulouse,

France) focused on dihydrogen and -borane

Ru complexes and presented recent results on

hydrogenation/dehydrogenation, hydrogen/deuterium

exchange and carbon dioxide functionalisation.

Luis Oro (University of Zaragoza, Spain) reported

a direct entry to amido Ir2 and Rh2 complexes,

by interaction of ammonia with alkoxo-bridged

precursors under mild conditions (Scheme I). In

particular, the dinuclear amido-bridged complex

promotes dehydrogenation of alcohols, affording

unusual mixed amido/imido Ir4 and bis(imido) Ir3

clusters. Theoretical calculations suggest that -NH2

linkages are crucial to the formation of hydrido

ammine Ir2 species, active in H-transfer reactions.

Claudio Pettinari (University of Camerino, Italy)

described the chemistry of Rh and Ir derivatives

containing scorpionate ligands and detailed the

reactions between [M(-diene)(μ-Cl)]2 dimers,

[M(Cp)Cl2]2 (Cp = cyclopentadienyl) and also [Ru(6-

arene)Cl2]2 with bis- and tris-(pyrazolyl)borates. Their

catalytic applications were also addressed.

Eric Clot (Institute Charles Gerhardt, Montpellier,

France) showed features of the chemistry of Ru-

borane complexes such as [RuH(X)(2-H2BR)(PR3)2].

With R = mesityl and X = H, the bis (BH) coordination

of borane was observed, whereas changing X = H to X

= Cl afforded the reversible formation of a borylene

complex. Density functional theory (DFT) calculations

described the nature of the coordination of the borane

to the Ru centre as a function of X and R.

Sanshiro Komiya (Tokyo UAT, Japan) presented

a study on the synergy of two different transition

metals (platinum and manganese) in catalysis and

showed that regio- and stereo-selective C−S bond

cleavage at dimethylthiiranes by heterodinuclear

R-Pt-Mn complexes, e.g. [Pt(Me)(dppe){Mn(CO)5}]

(dppe = 1,2-bis(diphenylphosphino)ethane), lead to

(thiamanganacycle)platinum compounds (8).

N

RhO

iPrN

N

NN

H

C

R

H

Fig. 5. Water activation by a rhodium catalyst



C−H and C−C Bond Activation and FunctionalizationAlan Goldman (Rutgers University, USA) focused on

pincer-ligated Ir complexes as catalysts for alkane

dehydrogenation, and discussed the mechanism,

the scope of dehydrogenations and coupling with

secondary reactions (tandem catalysis).

William Jones (University of Rochester, USA)

compared the reactivities of the nickel or rhodium

metal fragments [Ni(dippe)], [TpRhL], [Cp*RhL] and

[Rh(dippe)]– (dippe = 1,2-bis(diisopropylphosphino)-

ethane; Tp = tris(3,5-dimethylpyrazolyl)borate; Cp*

= pentamethylcyclopentadienyl; L = PR3 or CNR)

towards the cleavage of C−H, C–C and C–S bonds.

Georgiy Shul’pin (Semenov Institute of

Chemical Physics, Moscow, Russia) discussed the

functionalisation of C–H compounds with peroxides

catalysed by organometallic complexes of Os and

Rh. For example, [Os3(CO)12] (9) and [Cp*2Os] (10)

effi ciently catalyse the oxygenation of hydrocarbons

with hydrogen peroxide, while Rh carbonyl complexes

catalyse the oxygenation of benzene.

Maurice Brookhart (University of North Carolina,

USA) focused on useful hydrocarbon conversions

employing Ir pincer complexes capable of effi cient

transfer dehydrogenation and their application in

alkane metathesis, synthesis of aromatic molecules

from linear alkanes and synthesis of p-xylene from

ethylene as the sole feedstock (Scheme II).

Todd Marder (Würzburg University, Germany)

addressed the Ir-catalysed borylation of aromatic

C−H bonds, covering applications and issues affecting

selectivity. With Patrick Steel (Durham University, UK)

(11), they developed the microwave assisted borylation

of aromatic C−H bonds and one-pot, single solvent

processes for combined aromatic borylation (Suzuki-

Miyaura cross-coupling and aromatic borylation)

conjugate addition sequences. Marder described the

application of selective C−H borylation to the synthesis

of substituted 2-phenylpyridines and functionalised

pyrenes (Figure 6) (12). These processes rely on the

formation of pgm boryl complexes, and their unusual

properties.

David Davies (University of Leicester, UK)

described a Rh-catalysed ambiphilic metal ligand

activation (AMLA) of C−H bonds (Scheme III) and

determined, through DFT calculations, the relative

ease of this activation, similarly to other recently

reported work (13).

Robert Crabtree (Yale University, USA) clarifi ed that

with primary oxidants Ce(IV) and NaIO4, precatalysts

of the types [Cp*Ir(chel)Cl] (chel = 2,2-dipyridyl,

2-pyridylphenyl and related groups) mediate oxidation

of alkyl C−H to C−OH with retention of confi guration at

carbon. These oxidants (also, anodic oxidation) lead to

water being converted to dioxygen by [Cp*Ir(chel)Cl]

and [Cp*Ir(OH2)3]SO4. In some cases the catalysis is

homogeneous, in others heterogeneous, a distinction

HH

HN

H

N

Ir Ir

IrIr

NH3

MeOH

MeMe

OO

Ir Ir

H2N

H3NH

C OH

H

H H

H

N

H

N

Ir Ir

NIr Ir

H H

C

N

NIr

IrIr

H

H

Scheme I. Formation of amido and imido Ir2, Ir3 and Ir4 iridium cluster complexes



Dehydrogenation H2

Major MinoriPr2P Ir PiPr2

[Ir] =

Ethylene trimerisation

3

Feedstock

[Ir]

+

Scheme II. Iridium-catalysed synthesis of p-xylene from ethylene

1.1 B2pin2

Hexane, 80ºC, 16 h

[Ir(COD)(OMe)]2 1%dtbpy 2%

2.2 B2pin2

THF, 80ºC ,16 h

Bpin

BpinBpin

67%

94%

Pyrene HOMO

Fig. 6. Borylation of pyrene exclusively at the 2- and 2,7-positions using an iridium catalyst. B2pin2 and dtbpy stand for diboron pinacol ester and 4,4’-di-tert-butyl bipyridine, respectively (HOMO = highest occupied molecular orbital)

that is made from dynamic light scattering and quartz

crystal nanobalance measurements (Figure 7) (14).

Pierre Dixneuf (University of Rennes, France)

discussed the use of Ru(II)-cymene complexes,

assisted by coordinated or external bases, as catalysts

for a variety of arylation reactions from cheap and

available aryl and heteroaryl chlorides (15).

Andrew Weller (University of Oxford, UK) outlined

his recent studies on whether similar organometallic

structures, transformations and catalysis can occur

in the solid state, when compared to the analogous

solution-phase chemistry, using Rh and Ir phosphine

complexes. He demonstrated that C–H activation

(16), C–C bond formation and activation (17) and

B–H activation can all occur in the solid state. He also

discussed the characterisation of intermediates that

invoke sigma interactions.

Salvador Conejero (University of Seville, Spain)

showed that coordinatively unsaturated Pt(II)

14-electron complexes can intermolecularly activate

the C–H bonds of aromatic compounds, depending

on the electronic and steric properties of bulky

N-heterocyclic carbene (NHC) ligands, leading to

unsaturated Pt(II)-aryl complexes (18). A mononuclear



N

N

R1

R

R2

NH

N

R1

R

[Cp*Rh(MeCN)3]2+

Cu(OAc)2

NNH

R1

R

1

NN

R1

R

2

NNH

R1

R

3

R

NN

R1

R

4

RR1 = R2 = nPr, PhR1 = Ph; R2 = Me

RC CR2

[Cp*Rh(MeCN)3]2+

Cu(OAc)2

1: R = Ph 1, 3, 4: R = CO2Me 2: R = C(O)Me

Scheme III. Rhodium-catalysed activation of carbon–hydrogen bonds

N Ir

O

OH[Cp*Ir(H2O)3]SO4

Heterogeneous Homogeneous

No chelate ChelateNo buildup of deposit

500 ng buildup of deposit

M

ass,

ng

Curr

ent,

mA

Time, s Time, s

Time, s Time, s

1.0

0.8

0.6

0.4

0.2

0

–0.2

800

600

400

200

0

0 50 100 150 200 0 50 100 150 200

0 50 100 150 200 0 50 100 150 200

1.5 V 1.5 V

0.2 V 0.2 V

0.5

0.4

0.3

0.2

0.1

0

–0.1

800

600

400

200

0

Fig. 7. Distinguishing the homogeneity of electrocatalyst by quartz crystal electrochemical nanobalance data



Pt(III)-alkyl complex is an intermediate in carbon−

halogen coupling reactions.

Richard Adams (University of South Carolina,

USA) reported examples of oxidative addition

of gold−carbon bonds to Os cluster compounds

(Scheme IV). Because the H atom and the Au(PPh3)

group are both isoelectronic and isolobal, studies

of the reactivity of Au–C bonds may have important

implications for understanding the activation and

cleavage of C–H bonds.

Organometallic and Green ChemistryMunetaka Akita (Tokyo Institute of Technology, Japan)

described the use of clean and inexhaustible solar

energy to drive organic transformations via two

different catalytic tactics, i.e. bimetallic photocatalysis

and photo-redox catalysis, based on the unique

photochemical properties of the excited species of

[Ru(bipy)3]2+ (bipy = 2,2-bipyridine) and its organo-

Ir analogues. Their photo-excited states contain

singly occupied molecular orbitals of high and low

energies, which can work as reductant (electron

donor) and oxidant (electron acceptor), respectively.

Sequential redox processes led to effi cient generation

of organic radicals from enamines, organoborates

and trifl uoromethylating reagents. Sunlight effi ciently

induces Giese-type coupling and solvolytic olefi n

trifl uoromethylation.

Antonio Romerosa (University of Almería, Spain),

pursuing his work on water soluble, air stable hetero-

polymetallic polymers (19), presented several

examples of a family of compounds with formula

{[{(PTA)2(Cp)Ru−μ-CN−Ru(Cp)(PTA)2}-μ-MCl3-]}n (M =

Co, Cd, Ni, Cu, Pt and Pd) and their catalytic, biological,

optical and gel properties in water.

Polynuclear and Supramolecular AssembliesHani Amouri (Pierre and Marie Curie University, Paris,

France) reported a class of o- and p-quinonoid metal

complexes of the type [Cp*M(4-C6H4O2)]n (M = Ru,

n = –1; M = Rh or Ir, n = 0) (20). These compounds

were used as organometallic linkers in the synthesis

of supramolecular coordination assemblies with

luminescent properties. Such compounds show

panchromatic absorbance as well as red and near

infrared emission properties (Figure 8), and are

promising for optoelectronic and photovoltaic

applications (21).

Matti Haukka (University of Eastern Finland) addressed

the complexes [Rh(L)(CO)2]+ (L = 2,2-biimidazole,

2,2-bipyridine or 1,10-phenanthroline) which form

cationic one-dimensional chains in the solid state.

The Rh−Rh distances and the absorption properties

of the stacks can be effectively modifi ed by varying

the counter anions and solvents of crystallisation.

The neutral dinuclear [Rh2(R2bim)Cl2(CO)4] units

(R2bim = N,N-dialkyl-2,2-biimidazole) form neutral

chains with strongly anisotropic optical properties.

Another type of neutral chain structures consisting

of alternating cationic and anionic square planar

complexes is commonly found with Pt and Pd but

not with Rh.

Guo-Xin Jin (Fudan University, China) reported

an effi cient method for synthesising molecular

macrocycles of half-sandwich Ir and Rh complexes

via C−H and B−H activation with terephthalate and

dicarboxylate carborane, in order to construct

organometallic macrocycles with interesting

structural features and technologically useful

functions.

Os

Os Os

Os

OsOs

Os

OsOs

CO

CO

CO

–CO

CO

CO

CO

COOC

OCOC

OC

OC

OC

OC

OC

OC

CO

CO C

OCO

CO

CO

CO

CO

C O

C O

OC OC

O CMeCN

NCMe

Os3(CO)10(NCMe)2 Os3(CO)10(-C6H5)[-Au(PPh3)]

C6H5Au(PPh3)

Ph3PPh3P

Au Au

H

Os3(CO)9(3-C6H4)[-Au(PPh3)](-H)

Scheme IV. Oxidative addition of gold–carbon bonds to osmium cluster compounds



Organometallics for MaterialsBruno Chaudret (Institut National des Sciences

Appliqués (INSA), Toulouse, France) focused on the

synthesis and characterisation of Ru nanoparticles

stabilised by phosphines, phosphites and NHC ligands,

the characterisation of such particles, their surface

reactivity towards carbon monoxide and alkenes and

the infl uence of the ligands on styrene hydrogenation,

CO oxidation and CO hydrogenation.

Thomas Strassner (Technical University of

Dresden, Germany) discussed bis- and tetracarbene

Pt(II) complexes bearing bis(triazoline-5-ylidene)

and/or bis(imidazoline-2-ylidene) ligands, and

cyclometallated Pt(II) complexes with donating NHC

ligands (Scheme V). Such complexes show high

potential for application as triplet emitters in organic

light-emitting devices (OLEDs) (22–24).

Bioorganometallic and Bioinorganic ChemistryFabio Marchetti (University of Camerino, Italy) reported

potentially important anticancer Ru complexes,

obtained through conjugation of an (arene)Ru(II)

moiety with ligands that show biological activity:

acylpyrazolones, Schiff bases of acylpyrazolones,

curcumin and bis(pyrazolyl)methanes. The (arene)Ru(II)

curcuminates induce apoptosis by inhibiting tumour

cell proteasomes, bind DNA and activate caspase-3 in

cells and DNA fragmentation. Cationic (arene)Ru(II)

complexes with bis(pyrazolyl)methanes show a high

in vivo activity against an A17 model cell line (able to

generate metastases on various parts of the body) and

their antimetastatic activity is similar to or even higher

than that of the Ru(III) imidazolium trans-imidazole-

dimethylsulfoxidetetrachlororuthenate (NAMI-A)

M1

M2

NN

N

N

n

O

O

M1 M2 n

Ru1-Ru2 Ru Ru 1+Ru1-Rh2 Ru Rh 2+Ru1-Ir2 Ru Ir 2+Ru2 – Ru 1–Rh2 – Rh 0Ir2 – Ir 0

Mol

ar a

bsor

btiv

ity ×

103 , M

–1 c

m–1

60

40

20

0200 400 600 800

Wavelength, nm

RubpyRu1-Ru2Ru1-Rh2Ru1-Ir2

(a) (b)

1.00

0.75

0.50

0.25

0

Nor

mal

ised

inte

nsity

600 700 800 900Wavelength, nm

Ru1-Ru2Ru1-Rh2Ru1-Ir2

Fig. 8. Octahedral ruthenium, rhodium and iridium complexes with organometallic linkers: (a) panchromatic; and (b) red and near-infrared phosphorescence (77 K) of the complexes



complex, which recently entered phase II clinical

trials as one of the few active compounds against

metastases.

Vladimir Arion (University of Vienna, Austria)

focused on arene Ru(II) and Os(II) complexes with

indolobenzazepines (5 and 7, Scheme VI), also

referred to as paullones, with high antiproliferative

activity in human cancer cell lines. Searching for

structure-activity relationships, he replaced the

7-membered folded azepine ring with a fl at pyridine,

NH2

R

+

O

O

HH + + NH4Cl

O

H H

CH3IN

R

C C C N

R

N

N +

–I

N

N

Pt

R1

R2

O

O

1. Ag2O, dioxane, rt2. Pt(COD)Cl2, butanone, refl ux3. acacH, DMF, K(OtBu), rt to 100ºCN

N +

R1

–I

R2

Scheme V. Preparation of cyclometallated platinum(II) complexes with donating N-heterocyclic carbene ligands

HN

HN

NN

5

HN

NN

HN

6

HN

RuCl

N

N

HN

Cl

7 8 9

Cl ClHN

RuCl

NN

HN

HN

RuCl

N

HN

N

O

HN N O

Scheme VI. Indolobenzazepines (5) and indoloquinolines (6) and their arene ruthenium(II) complexes (7–9)



via a two-step procedure leading to another class of

biologically active compounds, indoloquinolines (6,

Scheme VI). Arene Ru(II) and Os(II) complexes with

indoloquinolines (8, Scheme VI) show 6- to 9-fold

higher antiproliferative activity than related systems

based on indolobenzazepines (25). In addition, arene

Ru(II) and Os(II) complexes with indolobenzazepines

bearing a stable 2,2,6,6-tetramethyl-1-piperidinyloxy

(TEMPO) radical unit (9, Scheme VI) have been

developed as potential anticancer drugs (26).

The attached electron paramagnetic resonance

(EPR) label should be explored for monitoring the

intracellular distribution.

João Rodrigues (Madeira University, Portugal)

addressed Ru containing dendrimers as important

alternatives to the clinically used Pt chemotherapeutic

agents; the preparation of poly(alkylideneamine)-

nitrile metallodendrimers functionalised with the Ru

moieties [Ru(dppe)2Cl]+ or [Ru(Cp)(PPh3)2]+ was

described, as well as their stability/degradation in

solution.

Maria Helena Garcia (University of Lisbon, Portugal)

described the family of compounds [Ru(5–C5H5)(PP)L]+

(L = mono- or bidentate N heteroaromatic -bonded

ligand, PP = diphosphine), and their interaction with

serum, nuclear proteins and DNA. In respect to the

latter, the planarity of L enables intercalation, as well

as other types of interaction (27).

Debbie Crans (Colorado State University, USA)

addressed the use of microemulsion solubilisation

as an alternative cancer treatment capable of

application in locations with limited facilities, and

described the development of an intracavitary

administration vehicle that delays administration

of carboplatin, eventually providing treatment of

metastasis after removal of a tumour, especially in

developing countries (Figure 9) (28).

Gerard Van Koten (Utrecht University, The

Netherlands) referred to the synthesis and

properties of pincer organometallics, their stability

and versatile catalytic properties, in particular the

directed inhibition of cutinase with a pincer-Pt

catalytic site (29).

Fundamental Organometallic ChemistryPierre Braunstein (Strasbourg University, France),

dealing with metallaligands and phosphoryl

migration reactions, illustrated the bonding versatility

of a functional 1,1-bis(diphenylphosphino)methane

(dppm)-type ligand bearing an oxazoline substituent

on the PCP carbon atom towards Pd(II) and Pt(II)

complexes, for both its neutral and monoanionic

forms. Whereas a chelating gem-diphosphine resulted

from migration of one of the PPh2 groups from a

phosphino-oxazoline nitrogen atom to carbon, the

reverse migration is triggered by metal coordination

and various H/phosphoryl tautomeric forms have

been stabilised (Figure 10).

Andy Hor (National University of Singapore)

devoted his talk to Pt hybrid NHC compounds.

The ligands (hybrid carbenes) have at least one

heterofunctional entity besides the carbene carbon

and may confer to their complexes structural diversity,

additional reactivity and functional applications in

photoluminescence, catalysis, electrochemistry, etc.

Michael Bruce (University of Adelaide, South

Australia) described the types of complexes

obtained through the reactions of polycyano-

alkenes, particularly tetracyanoethene (TCNE) and

tetracyanoquinodimethane (TCNQ) with [Ru(CC−R)-

(PPh3P)2Cp] (R = H, Ph) or [Ru(CCR)(dppe)Cp*],

among others.

Anthony Hill (Australian National University)

reviewed the synthesis of a variety of bi- and

Surgical removal of Implant introduction and Local and systemic treatment; tumour mass wound closure implant biodegradation

Carboplatin

O

OO

O

PtNH3

NH3

H

H

Fig. 9. Implantable formulation containing anticancer agent carboplatin for post-surgical treatment



polymetallic molecular carbido complexes resulting

either from condensation of metal halides and

lithiocarbynes, selenocarbonyl ligand cleavage (30),

oxidative addition of halocarbynes, or carbon disulfi de

activation.

Pierre Le Gendre (University of Burgundy, France)

described the synthesis of the mixed P-olefi n ligand

(3,5-cycloheptadienyl)diphenylphosphine, whose

conformational fl exibility and the relative position

of the two double bonds in regard to the phosphorus

atom promoted coordination diversity (31).

Mark Gandelman (Israel Institute of Technology)

presented the fi rst examples of nitrenium ions as

ligands for pgms (32), and discussed their preparation,

structures, unique properties and reactivity.

Elena Shubina (A. N. Nesmeyaov Institute of

Organoelement Compounds (INEOS), Moscow,

Russia) discussed the role of hydrogen bonds in the

chemistry of transition metal hydrides (namely of

Ru and Os) which can act either as proton donors or

proton acceptors. The proton transfer between two

transition metal hydrides with opposite polarities

may lead to the formation of M-H–···+H-M dihydrogen bonds (33), which precedes the proton

transfer and the development of μ,1:1-H2 species

featuring an end-on coordination mode between

the two transition metals.

Reaction MechanismsKonstantin Luzyanin (Technical University of Lisbon,

Portugal) showed that Pd-mediated dipolar cycloaddition

of nitrones (Scheme VII) to isocyanides opened a

route to complexes with new types of NHC ligands.

The mechanism of this reaction was studied by

theoretical (DFT) methods. The structures of the

cycloaddition products, the transition states, the kinetic

and thermodynamic parameters of the reactions and

solvent effects were rationalised.

Philippe Kalck (University of Toulouse, France)

proposed a role of the acetato ligand within the

reductive elimination step in the industrially

important Rh-catalysed methanol carbonylation

reaction (Scheme VIII). At low water content, the rate-

determining step was demonstrated by high pressure

nuclear magnetic resonance (HP-NMR) observations,

kinetic measurements and DFT calculations to be the

reductive elimination of acetic anhydride from the

intermediate [RhI2(COCH3)(COOCH3)(CO)2]–. This

reaction pathway is largely exergonic.

ElectrochemistryWolfgang Kaim (University of Stuttgart, Germany)

showed how the ligand redox system Qn–

[Q = 4,6-di-tert-butyl-(2-methylthiophenylimino)-

O N

Ph2P PPh2H

CH2Cl2

O N

Ph2P

PPh2

Stable as free ligands Stabilisation by metal coordination required

O N

PPh2

PPh2

O N

Ph2P PPh2

H

Tautomeric/isomeric forms

Fig. 10. Illustration of the versatility of an oxazoline functionalised dppm ligand

ON+

–

N

O

HC

H

N R2

C

O

R3

R2

R3

NO

H

–

+Cl

ClPd

ClClPdPd

Cl

ClC

NR

CN

R

CN

R

CN

R

CN

R

C

NR

C6H6, 5ºC, 4 h

Route A

C6H6, 5ºC, 2 h

Route B

R = Cy, tBu, Xyl, C6H4OMe-4; R2 = Me, CH2Ph; R3 = C6H4Me-4

* *

Scheme VII. Dipolar cycloaddition of nitrones mediated by palladium complexes



o -benzoquinone; n = 0, 1, 2] provided options for

transition metal coordination, involving changes

of charge state and binding mode, and, by using

[Ir(C5Me5)(Q)]0/+/2+, [M(C6R6)(Q)]0/+/2+ (M = Ru,

Os) and [M(Q)2]2–/–/0/+/2+ (M = Ni, Pd, Pt, Ru, Os)

as examples, he demonstrated how redox activity

(‘non-innocence’) and preferred coordination

number are related.

Fabrizia Fabrizi de Biani (University of Siena, Italy)

addressed the topic of molecular metal clusters for

molecular electronics by reviewing the electron

transfer properties of a heterogeneous collection of

metallic clusters including low- to high-nuclear Pt

clusters. In this respect, Pt6 clusters were found to have

a transistor-like behaviour (34).

Olivier Buriez (École Normale Superieure, Paris,

France) electrochemically grafted at a Pt surface,

by oxidation of the ferrocene moiety, a π-conjugated

ferrocene-aniline (10, Scheme IX) possessing

anticancer properties. The mechanism relies on an

intra-molecular electron transfer between the amino

and the electrogenerated ferricenium moiety which

allows the indirect oxidation of the amino group.

The radical cation thus formed is then prone to react

with a base (collidine) to produce the corresponding

aminyl radical that may add onto the Pt surface (35).

Scheme IX. Electrochemical grafting of a ferrocenyl aniline anticancer drug onto a platinum surface (SCE = saturated calomel electrode)

Scheme VIII. The role of acetato ligand in rhodium-catalysed methanol carbonylation

Fe

NH2

10

–e (+ 0.4 V/SCE)

Fe

NH2

Fe

NH2

+

+

Fe

NH

N N

H+

HN

FePt

COCH3

CO

CORh

I

I

I

fac, cis(or 3 kcal mol–1/trans, mer) –28 kcal mol–1 –43 kcal mol–1

+OAc–

–I–

COCH3

CO

CORh

I

CH3COO

I

CO

CORh

I

I+ CH3COOCOCH3



ConclusionsThe success of the XXV International Conference on

Organometallic Chemistry and the important role

played by the pgms in so many of the contributions,

as illustrated in this review, demonstrate conclusively

that organometallic chemistry as a whole, and in

particular that involving pgms, is crucial to developing

both fundamental and applied chemistry in many

signifi cant areas.

The XXV ICOMC succeeded in achieving its main

aims: to contribute to the promotion of excellence

in science, of international research collaboration

and of the universal character of science, which also

constitute main objectives of the International Council

for Science (ICSU Strategic Plan, 2012−2017). The next

conference in the series is to be held in Japan in 2014.

AcknowledgementsWe thank the conference participants who have kindly

provided illustrations of their works.

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The ReviewersM. Fátima C. Guedes da Silva is a researcher at the Centro de Química Estrutural, IST, and Associate Professor at the Universidade Lusófona de Humanidades e Tecnologias (ULHT), Lisbon, Portugal. Her main research interests are: structural determination, by X-ray diffraction analysis, of metal complexes and organic compounds, metal polynuclear assemblies and supramolecular structures; activation, by transition metal centres, of small molecules with biological, pharmacological, environmental or industrial signifi cance; and mechanistic investigation of fast reactions mainly by digital simulation of cyclic voltammetry.

Armando J. L. Pombeiro is a Full Professor at the Instituto Superior Técnico (IST, Technical University of Lisbon, Portugal), Vice-President of the Class of Sciences of the Academy of Sciences of Lisbon, and President of the Portuguese Electrochemical Society. Among many other honours he was also Chairman of the XXV ICOMC. His research group is active in the following areas: activation of small molecules with industrial, environmental or biological signifi cance by metal centres; metal-mediated synthesis and catalysis; catalysis in aqueous media; crystal engineering of coordination compounds, self-assembly of polynuclear and supramolecular structures; molecular electrochemistry of coordination compounds, redox potential-structure relationships and ET-induced reactions; and theoretical studies.

� •Platinum Metals Rev., 2013, 57,�(1),�32–43•


Photocatalytic Activity of Doped and Undoped Titanium Dioxide Nanoparticles Synthesised by Flame Spray PyrolysisPlatinum-doped TiO2 composites show improved activity compared to commercially available product


Irene E. Paulauskas and Deena R. Modeshia

Bio Nano Consulting Ltd, 338 Euston Road, London NW1 3BT, UK,

and London Centre for Nanotechnology, University College London, 17–19 Gordon Street, London WC1H 0AH, UK

Tarek T. Ali, Elsayed H. El-Mossalamy, Abdullah Y. Obaid and Sulaiman N. Basahel

Chemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589, Saudi Arabia

Ahmed A. Al-Ghamdi

Physics Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589, Saudi Arabia

Felicity K. Sartain*

Bio Nano Consulting Ltd, 338 Euston Road, London NW1 3BT, UK

*Email: [email protected]

The photocatalytic activities of a series of titanium dioxide (TiO2) based nanoparticles, synthesised via flame spray pyrolysis (FSP), have been investigated and compared with the commercially available Evonik Aeroxide® TiO2 P 25 (P 25). The effects of metal ions aluminium, tin and platinum, respectively, on the physical and chemical properties of the TiO2 nanoparticles are reported. The set of six samples were characterised by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma-mass spectrometry (ICP-MS) and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. Specific surface areas were determined using nitrogen adsorption and desorption measurements. Subsequent photocatalytic studies of the degradation of methyl orange (MO) dye under UV irradiation demonstrated that addition of Al and Sn had a negative effect on catalytic performance, whereas the addition of ≤0.7 at% Pt to each sample enhanced photocatalytic activity. Most interestingly, the Pt-doped composite samples (TiO2-Sn/Pt and TiO2-Al/Pt) both showed a significantly higher rate of degradation of MO, when compared to P 25. All Pt-doped samples show an increased visible photon absorption capacity. The relationships between the physical and chemical characteristics are discussed in relation to photocatalytic performance.

1. IntroductionThe use of semiconductors as materials for photocatalytic applications has been intensively studied since Fujishima and Honda reported their water electrolysis work in 1972 (1). Research into the development of photocatalysts for environmental applications was subsequently initiated by Frank and Bard (2) who investigated the use of TiO2 powder for the decomposition of highly polluting cyanide ions in water. Following these studies, photocatalysis using TiO2 for the degradation of wastewater pollutants has attracted a lot of attention due to its inherent

http://dx.doi.org/10.1595/147106713X659109� •Platinum Metals Rev., 2013, 57,�(1)•


photoactivity, chemical and biological stability, non-toxicity, low cost and well known synthesis methods (3). Numerous approaches have been applied to improve the effectiveness of TiO2, and one, which is now well established, is the use of nanoparticles rather than a bulk powder.

The functional performance of nanoparticles is directly dependent on their particle size, nanostructure and morphological organisation (4, 5). Thus, it is clear that the method of synthesis will strongly influence the photocatalytic activity of the final compound. A number of techniques for the synthesis of TiO2 have been reported, including hydrothermal methods (6), sol–gel methods (7) and flame synthesis (FSP) (8). Of these, FSP represents an ideal synthetic method since its versatility allows for fast and cost-effective mass production of homogenous nanoparticles. Its use for the production of undoped and doped TiO2 has been widely reported in the literature (9–11) and, when compared with more traditional wet chemistry techniques, it provides a methodology that facilitates the synthesis of homogeneously doped materials (12).

Composite/coupling formation and doping of TiO2 are examples of other approaches used to improve efficiencies, where generally the aim is to increase the separation between the photogenerated electrons and holes and thus improve upon the low quantum yield (13). Addition of such elements tends to alter the aggregate size and morphology of the bulk TiO2, whilst also conferring phase changes within the crystal structure, which in turn alter the band gap of the photocatalyst. Anatase, rutile and brookite are the three distinct crystallographic forms of TiO2, of which anatase is widely accepted to be most photocatalytically active (14). It should be noted that efficiencies of TiO2-based catalysts are not solely influenced by one pure phase but by the ratios of different phases present; an excellent example of this is Evonik Aeroxide® TiO2 P 25 (P 25), which consists of a mixture of two phases (~75% anatase and ~25% rutile) (8, 14, 15), and has been shown to have higher photocatalytic activity than pure anatase (10, 15). To this end, several doping elements and oxides have been incorporated into TiO2 nanoparticles; these include Sn (10, 16), Al (17, 18), Pt (19, 20), iron(III) oxide (Fe2O3) (21), tungsten trioxide (WO3) (22), and zinc oxide (ZnO) (23, 24). Furthermore, it has also been reported that introducing two metal ions onto nanocrystalline TiO2 particles, rather than mono-doping them, leads to an improved photocatalytic performance (25).

The addition of either Sn (16) or Al (17) to TiO2 nanoparticles has been reported to result in an improved photocatalytic performance for the degradation of dye molecules, when compared to undoped TiO2 samples. Similarly, the synthesis of Pt-doped TiO2 in a flame aerosol reactor has been reported to have a positive effect on the degradation rate of MO with a Pt loading of 0.5% when compared with undoped samples of similar surface area (20). However, the combined effect of these elements in TiO2 and their effect on the photocatalytic properties for the degradation of organic compounds have been less well investigated.

In this study we compare the activity of undoped TiO2, Sn-doped TiO2, Al-doped TiO2 and Pt-doped TiO2 nanoparticles with undoped TiO2 and Pt-doped composite materials synthesised via the FSP technique, as well as with the commercially available P 25. We discuss the general morphology, specific surface area, phase composition, absorption range and photocatalytic behaviour of these particles as a function of the degradation rate of MO, a model organic pollutant/dye, in the presence of UV irradiation.

2. Experimental2.1 Sample PreparationSamples were prepared using a FSP technique, where a liquid precursor feed – metal precursor(s) dissolved in a solvent – is sprayed with an oxidising gas into a flame zone. The spray is combusted and the precursor(s) are converted into nano-sized metal or metal oxide particles, depending on the metal and the operating conditions (26). The technique is flexible and allows the use of a wide range of precursors, solvents and process conditions, thus providing control over particle size and composition. All the samples produced were TiO2-based nanoparticles. The liquid precursor feeds consisted of appropriate mixtures of platinum acetylacetonate (Alfa Aesar), titanium ethoxide (Aldrich), tin 2-ethylhexanoate (Alfa Aesar), aluminium(III) tri-sec-butoxide (Alfa Aesar) and xylene (Fisher). The concentration of the reactants was 0.5 mol l–1. The Al:Ti and Sn:Ti molar ratios were kept at 0.14 and 0.7, respectively, while the Pt loading was kept at ca. 0.4 at% in all doped catalysts.

In a typical run, a flow of 5 ml min–1 of liquid precursor solutions was delivered to the nozzle using a syringe pump (Kd Scientific, KDS200). The precursor solutions were then atomised by 5 l min–1

of dispersant O2 while maintaining a pressure drop between 1–1.5 bar at the nozzle tip. The combustion of



the dispersed droplets by the surrounding supporting methane/oxygen (1.5 l min–1/3.2 l min–1) formed the main core flame. A sintered metal plate ring provided an additional O2 sheath flow (5 l min–1) surrounding the supporting flame. Calibrated mass flow controllers (MKS Instruments) were used to monitor all gas flows. Product particles were collected on a glass microfibre filter (Whatman GF/A grade, 15 cm in diameter) with the aid of a vacuum pump (Busch Seco SV 1025 C pump from West Technology Systems).

The following six samples were synthesised: FSP-TiO2, TiO2-Al, TiO2-Sn, TiO2/Pt, TiO2-Al/Pt and TiO2-Sn/Pt. In order to obtain a reference for effectiveness of these samples, commercially available Evonik Aeroxide®

TiO2 P 25 (donated for this study) was investigated in parallel.

2.2 Sample CharacterisationTEM analysis was performed to determine basic morphology and the average particle size of the TiO2 nanoparticles. The instrument used was a high-resolution JEOL 2010 TEM microscope. The samples were prepared by suspending 10 mg of the mixed oxide in 5 ml ethanol followed by ultrasonication for 5 min. 0.5 ml of the suspension was dropped on top of a copper mesh for TEM imaging and dried in air.

Elemental analysis was carried out as follows: samples were prepared by dissolving 10 mg of the TiO2 nanoparticles in 4 ml sulfuric acid at 523 K for up to 1 h. The solution was subsequently allowed to reach room temperature and any undissolved matter was removed by using a 0.2 mm PTFE Millipore membrane filter. ICP-MS analysis was conducted using a Perkin Elmer/Sciex ELAN® Dynamic Reaction Cell (DRCPlus) coupled with a Perkin Elmer AS-93plus Autosampler with Elan v. 3.3 software for data collection. A crossflow nebuliser was used with a Scott spray chamber and the basic settings consisted of a RF power of 1100 W, a plasma gas flow of 15 l min–1, a nebuliser flow of 0.97 l min–1 and a sample flow rate of 0.4 ml min–1.

XRD analysis of all the samples was determined at room temperature using an X’Pert PRO powder diffractometer (PANalytical BV, The Netherlands) with a silver anode X-ray source and a scintillating crystal detector. The samples were scanned over a 2θ range of 25º–70º in steps of 0.01º.

The surface area analysis was made using a Tristar 3000 Micromeritics instrument, and the software used was the Tristar 3000 v. 6.04. This analyser uses physical adsorption and capillary condensation principles to obtain information about the surface area and porosity of a solid material. More specifically, the adsorption

and desorption isotherms of N2 were carried out at 77 K. Specific surface areas were calculated according to the Brunauer, Emmet and Teller (BET) equation from the adsorption isotherm. The pore-size distribution of the samples was calculated from desorption branch using the Barrett, Joyner and Halenda (BJH) method.

UV-vis diffuse reflectance measurements were carried out at room temperature and performed on a Perkin-Elmer Lambda 950 spectrophotometer equipped with an integrating sphere to test absorption shifts in the wavelength range from 300 to 500 nm.

2.3 Photocatalysis StudyPhotocatalytic activity measurements were carried out in a custom-built reactor, details of which have been previously reported (24). The model dye solution selected for this study was methyl orange (MO) and a standard solution of 10 mg l–1 was used. In a typical experiment, 50 mg of the TiO2-based nanoparticles to be tested were added to 100 ml of the MO solution and mixed in an ultrasonic bath for 5 min, then placed into the reactor. Once in the reactor, the solutions were stirred at 300 revolutions per minute (rpm) for 30 min in the dark at room temperature to allow for chemisorption to occur. Once this time had elapsed, a sample of the solution was taken, and the remaining reaction solution was irradiated with UV light. Further samples were taken every 5 to 10 min until all of the MO had degraded.

Using the UV-vis spectrophotometer, the absorbance peak of each sample solution was measured at 465 nm to determine the MO concentration. The reaction rate constant (k) was then estimated assuming first order kinetics using Equation (i):

(i)

where C0 is the initial concentration, C is the concentration at time t, and k is the reaction rate constant. This procedure was repeated three times with fresh nanoparticles each time to determine the standard deviation of the measurement.

3. Results and Discussion3.1 CharacterisationThe morphologies of the TiO2-based catalysts were investigated by TEM (see Figure 1) and the common issue of agglomeration of nanoparticles was observed in each sample, which meant that it was not straightforward to find single monolayers.

0 –Cln ktC

=



The FSP-TiO2 particles were found to be regular in shape (polyhedral) with a size distribution between 5 and 20 nm, comparable to the other samples except for those containing Al, which on average showed a larger particle size. For the TiO2-Al and TiO2-Sn samples the particles appeared to become more rounded, however there was no visible addition of the respective metal ions observed (data not shown). For the TiO2/Pt sample the TiO2 crystalline planes were easily observed, but they were found to have poor homogeneity with very irregular

shapes and the size distribution was determined to be between 5 and 20 nm. Although the Pt doping particles were too small to be characterised by chemical analysis techniques such as energy dispersive X-ray spectroscopy, the presence of small dark particles on the surface of the TiO2 (Figure 1(d)) can be observed. This result is also consistent with previous observations found in the literature (20), and indicates that unlike the Sn and Al ions the Pt ions remain on the surface of the TiO2 rather than being incorporated into the crystal lattice.

(a)

50 nm 20 nm

(b) (c) 20 nm

(d) 5 nm (e) 20 nm (f) 5 nm

(g)

20 nm

(h)

5 nm

Fig. 1. TEM images of doped and undoped TiO2 nanoparticles synthesised by FSP: (a) and (b) FSP-TiO2; (c) and (d) TiO2/Pt; (e) and (f) TiO2-Sn/Pt; and (g) and (h) TiO2-Al/Pt



Interestingly, the TiO2-Sn/Pt nanoparticles were found to be more rounded than the TiO2/Pt, having a comparable platelet size with the distribution also ranging between 5 and 20 nm. In this sample no significant feature was depicted that could be attributed to the Pt dopant. The TiO2-Al/Pt nanoparticles were also more circular, but with less uniform edges and had a larger size distribution ranging between 5 and 30 nm. Additionally, in this case some dark particles comparable to those observed in the TiO2/Pt sample were also seen (Figure 1(h)).

Results from the ICP elemental analysis revealed that there was only a fractional deviation between the theoretical and actual percentages for each of the TiO2 samples synthesised that contained additional metal ions (see Table I). The atomic percentages of Al and Sn were larger – 14 at% and 7 at% respectively – than for the Pt ion (≤0.7 at%), so only Pt can be truly considered as a dopant in these samples. The rationale for making the Al and Sn composites with varied at% was that from previous studies it had been found that at each of these respective percentages the balance of anatase to rutile phases shifted such that the rutile phase in TiO2 was dominant (data not shown).

The XRD pattern of the FSP-TiO2 sample (see Figure 2) showed that the anatase polymorph

dominates (19, 27, 28). Smaller peaks were observed at 2θ values of 27º and 36º (27) and are indicative of the rutile polymorph. The addition of Al, Sn and the Pt dopant resulted in a variation in the ratio of rutile and anatase across all of the samples (Figure 2). Synthesis of TiO2 with Al and Sn respectively significantly altered the phase ratio, with the rutile phase being the dominant phase in each sample, as anticipated. The TiO2/Sn sample showed a higher proportion of rutile phase to anatase, despite having a lower at% of the composite metal compared to the TiO2/Al sample. This can, in part, be explained by comparing the valence and ionic radii of the respective composite metals with those of Ti4+. Substitution of the Ti4+ (ionic radius: 0.61 Å) ions by other ions of similar ionic radius induces a shift in phase from anatase to rutile (Al3+ = 0.53 Å, Sn4+ = 0.69 Å) (10, 19). Thus, the matching valence and comparable atomic radii of Sn4+ and Ti4+ suggests that substitution between the two can occur readily and induce the observed alteration in phase ratio.

Given the high at% of the samples with Al and Sn, it is plausible to assume the presence of their respective metal oxides; however, for the TiO2-Al sample the Bragg reflections associated with such phases have not been observed via XRD. In the TiO2-Sn diffractogram, the sharp peak at ~33º is consistent

Table I

Characterisation Results for the Synthesised and Commercial Titanium Dioxide Nanoparticles

(Doped and Undoped)

Nanoparticles Preparation, at% (Sn or Al/Ti), (Pt/Ti)

ICP, at%(Sn or Al/Ti), (Pt/Ti)

Surface area,m2 g–1

Particle size,nma

Reaction rate constant,k, × 10–3 s–1

P 25 n/a n/a 58 n/a 0.90 ± 0.20

FSP-TiO2 n/a n/a 88 5–20 0.36 ± 0.02

TiO2/Pt 0.4% 0.4% 81 5–20 0.57 ± 0.07

TiO2-Sn 7% 7% 80 5–20 0.18 ± 0.03

TiO2-Sn/Pt 7%, 0.4% 7%, 0.3% 74 5–20 2.30 ± 0.20

TiO2-Al 14% 15% 42 10–30 0.18 ± 0.02

TiO2-Al/Pt 14%, 0.4% 14%, 0.7% 90 5–30 2.75 ± 0.60

a From TEM images



with flame-made Ti-Sn oxides (10) that exhibited a similar peak at 33.9º corresponding to the (101) plane of SnO2. In this instance, the SnO2 particles within the structure act as seed nuclei favouring the formation of rutile TiO2 (10). In the case of Al, where substitution of the dopant also infers a change in valence, it has been reported that doping can create oxygen vacancies in the TiO2 matrix, which favours the anatase to rutile transformation (12).

The addition of Pt to the samples had less impact on the ratio between the phases, with the proportion of rutile increasing in the TiO2-Al/Pt sample, and also in the TiO2/Pt sample but to a lesser extent compared to their respective undoped samples. The SnO2 was lost in the TiO2-Sn/Pt sample. The promotion of the rutile phase in the Pt-doped TiO2 and TiO2-Al samples could be attributed to the generation of the dopant metal oxide during synthesis, which is possible through the substitution of a Ti4+ ion with Pt4+ which has a similar ionic radius of 0.63 Å. This in turn may also provide a nucleation site for rutile TiO2 (10, 19). The addition of the Pt to the composite samples resulted in each of them being composed of anatase to rutile phases in an approximate ratio of at least 20:80, despite the

variances in at% of the Sn4+ and Al3+. Additionally, for both the TiO2-Al and TiO2-Sn composites after doping with Pt there was a reduction in crystallite size, as indicated by the broader peaks recorded for each powder sample.

The surface area of the FSP-TiO2, determined by BET, was found to be ~88 m2 g–1, which is larger than that recorded for the commercially available P 25 (~58 m2 g–1). The addition of Sn resulted in a slight decrease in surface area, whereas addition of Al caused a significant decrease to 42 m2 g–1. The observed decrease may be attributed to the creation of oxygen vacancies upon Al3+ substitution with Ti4+. In turn, this enhances oxygen diffusion, which increases the sintering rate and thus particle size (previously observed by TEM analysis) (10). The addition of the Pt dopant to the TiO2-Al sample resulted in a recovery of the surface area to 90 m2 g–1; whilst upon Pt doping the TiO2 and TiO2-Sn samples, a slight decrease was observed compared to TiO2 and TiO2-Sn, respectively (Table I). The surface area for all the Pt-doped samples was larger than that of the commercially available P 25. The porosity of the samples was also calculated from the adsorption branch of the isotherms using the BJH formula. For all

25 30 35 40 45 50 55 60 65

Diffraction angle, º2θ

Diff

ract

ed in

tens

ity, a

rbitr

ary

units

FSP-TiO2

TiO2-Al

TiO2-Sn

TiO2/Pt

TiO2-Al/Pt

TiO2-Sn/Pt

P 25

A

R R RR RAA A

A AAA

Fig. 2. XRD diffraction patterns for the six TiO2 based FSP synthesised materials and the commercially available P 25 sample for reference. Peaks representative of the anatase (A) and rutile (R) phases are labelled accordingly



of the samples, nitrogen adsorption isotherms showed a hysteresis loop typical of mesoporous materials (type IV isotherm according to the International Union of Pure and Applied Chemistry (IUPAC) classification). This is indicative of porosity between particles rather than within individual particles (11).

Finally, the band gap of each of the samples was determined using UV-vis diffuse reflectance measurements (see Figure 3). The band edges for all samples were found to be in the UV region, which suggests that they will all be photocatalytically active under UV irradiation (350–400 nm). Interestingly, the absorption range of the FSP-TiO2 was almost identical to that of P 25 and a red-shift was observed in the absorption range of both the TiO2-Al and TiO2-Sn when compared to the undoped TiO2. Previously it has been reported that such a shift is indicative of the incorporation of metal ions into the TiO2 framework (17) and, additionally, of the presence of the rutile phase within the structure (14). The addition of Pt dopant to the samples resulted again in slight changes in the absorption range; in the case of TiO2/Pt a small red-shift was seen, but for the composite samples a slight blue-shift was observed. It should be noted that by comparison with the FSP-TiO2, the absorption range for all of the other samples was red-shifted. Interestingly, all the Pt samples showed that they have an increased visible photon absorption capacity, something which distinguishes them from all the other samples tested.

3.2 Photocatalytic Degradation of Methyl Orange DyeThe photocatalytic activity of each sample was investigated by monitoring the photodegradation of MO dye and in all cases the initial concentration of the MO solution was 10 mg l–1. Since in most cases an exponential decay was recorded, the photoactivity profile of each TiO2 sample was fitted assuming first order kinetics, as described in Section 2.3 and by Equation (i). The commercially available P 25 TiO2 sample was also investigated, to provide a benchmark against which the catalysts synthesised using FSP could be measured. The intial rate of reaction using the FSP-TiO2 was approximately half of that determined for the P 25 sample (Figure 4 and Table I), despite the former having a significantly larger surface area. This difference is likely to be due to a combination of factors, including the slight variance in the ratio between the anatase and rutile phases, and the activity of the FSP-TiO2 sample may be reduced due to the presence of residual carbon generated during

the combustion process. Additionally, P 25 is known to have a unique microstructure, which enables intimate contact between the phases and, in turn, increases the efficiency of the electron-hole separation (19).

Comparing the FSP-TiO2 with the TiO2-Al and TiO2-Sn samples, both the latter samples showed a reduced photocatalytic performance compared with the undoped sample (Figures 4 and 5). The BET analysis indicates that there was little difference between the surface areas of the TiO2-Sn and TiO2 samples, whereas the TiO2-Al sample had a surface area almost half that of the former two samples. This observed reduction in surface area for the TiO2-Al sample provides an explanation for its slower rate of reaction. However, the TiO2-Sn sample had the slowest rate constant of all the samples investigated, despite having a comparable surface area to the more reactive samples. This reduced rate of reaction may be due to having a significant fraction of the surface occupied by SnO2. The small red-shift in the absorption bands and the XRD diffractograms recorded for the composite samples may provide some rationale for these results. The addition of the metal ions Al or Sn resulted in a significant shift in the ratios of the crystal phases present in the structure, with an increase in the amount of rutile being observed compared to the undoped TiO2.

The addition of the Pt dopant to all the samples was shown to improve reaction rates and in the case of TiO2-Al and TiO2-Sn approximately a 10-fold and 5-fold enhancement in photocatalytic activity, respectively, was recorded. In fact the TiO2-Al/Pt and TiO2-Sn/Pt samples had the highest MO degradation rates compared to the other samples, including P 25 (Figure 4). The addition of Pt in all cases conferred a slight increase in the content of rutile within the TiO2 nanoparticles, a phenomenon previously observed when similar compounds were synthesised by FSP (19). Bickley et al. (14) have discussed at length the multiphasic nature of P 25 TiO2, and suggest that it is the complex relationship between anatase and rutile phases that contributes to its high photocatalytic activity. Here, the addition of the metal ions, in their respective ratios, appears to generate such biphasic TiO2-based materials. This, along with the comparably large specific surface areas and enhanced visible light absorption observed for all of the FSP samples after Pt doping, may explain the enhanced activity measured.

Additionally, it has been reported that doping TiO2 nanoparticles with Pt improves photocatalytic activity (19, 20). However, it is important to control



1

0.8

0.6

0.4

0.2 0

Abs

orba

nce

300 350 400 450 500 550 600

Wavelength, nm

TiO2-Sn

TiO2-Pt/Sn

TiO2-Al

TiO2-Al/Pt

(b)

P 25

1

0.8

0.6

0.4

0.2

0

Abs

orba

nce

300 350 400 450 500 550 600Wavelength, nm

FSP-TiO2

TiO2/Pt

TiO2-Al

TiO2-Sn

(a)

Fig. 3. UV-vis diffuse reflectance spectra of the TiO2-based samples: (a) P 25, FSP-synthesised TiO2, TiO2-Al, TiO2-Sn and TiO2/Pt; (b) Pt-doped TiO2 nano-composites, TiO2-Al and TiO2-Sn samples are also shown for comparison. Shaded area indicates the irradiance range of the UV light source used for the photocatalytic activity studies



500 1000 1500

1.2 1 0.8 0.6 0.4 0.2

(b)

Time, seconds

P 25

FSP:TiO2

TiO2/Pt

TiO2-Al

TiO2-Sn

–Ln(

C/C o

)

0

Met

hyl o

rang

e co

ncen

trat

ion,

%

1000 2000 3000 4000

P 25

FSP-TiO2

TiO2/Pt

TiO2-Sn

(a)

100

80

60

40

20

Time, seconds

TiO2-Al

0

Fig. 4. Photocatalytic degradation of the methyl orange solution by the P 25 FSP-synthesised TiO2, TiO2-Al, TiO2-Sn and TiO2/Pt: (a) Change in the methyl orange concentration as a function of time; (b) Estimation of the initial reaction rate constant based on Equation (i)

the concentration of Pt used since photocatalytic properties tend to decrease as the Pt concentration increases above 1 at% (19). From the ICP analysis

it was found that 0.4, 0.3 and 0.7 at% Pt had been added to the TiO2, TiO2-Sn and TiO2-Al respectively, and each gave an improved performance over their



500 1000 1500

(b)

Time, seconds

TiO2-Sn

TiO2-Sn/Pt

TiO2-Al

TiO2-Al/Pt

–Ln(

C/C o

)

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

Met

hyl o

rang

e co

ncen

trat

ion,

%

1000 2000 3000 4000

TiO2-Sn

TiO2-Sn/Pt

TiO2-Pt/Al

(a)

100

80

60

40

20

Time, seconds

TiO2-Al

0

Fig. 5. Photocatalytic degradation of the methyl orange solution by the Pt-doped TiO2 nano-composites, TiO2-Al and TiO2-Sn samples are also shown for comparison: (a) change in the methyl orange concentration as a function of time; (b) estimation of the reaction rate constant based on Equation (i)

undoped equivalents. The TEM analysis clearly showed the presence of Pt on the surface of the TiO2/Pt and TiO2-Al/Pt samples, though this feature was less apparent than that observed in the TiO2-Sn/Pt sample. The presence of such particles on the surface can lead to increased efficiency of electron-hole separation by trapping or removing electrons from the TiO2 surface

(19, 20), and this in turn can result in enhanced photocatalytic activity.

4. ConclusionsSix TiO2-based nanocatalysts were synthesised using a FSP technique and it was found that the addition of Al and Sn to the TiO2, at a ratio of 0.14 and 0.7, respectively,



resulted in significant phase changes within the crystal structure. In the former case there was a large decrease in surface area which could be attributed to an increase in oxygen vacancies, which in turn increases the particle size. For each of these composite samples a reduction in photocatalytic activity was observed when compared to the pristine TiO2. Conversely, the addition of Pt as a dopant in all samples resulted in an enhancement in photocatalytic activity, with both the TiO2-Al/Pt and TiO2-Sn/Pt samples having a higher reactivity than the commercially available P 25 in degrading methyl orange.

The effects of surface area, ratios of crystal structure, and the metal dopants have been discussed to provide rational explanations for the photocatalytic activities observed. Due to the complex nature of these multiphasic and doped materials it is not straightforward to determine the precise relationship between the surface and bulk properties which result in the enhancements seen, and further studies are required to fully understand the interactions between the chemical and structural properties of these materials.

AcknowledgementsThe authors thank Peter Bishop, Benedicte Thiébaut, Weiliang Wang, Gregory Goodlet and the Analytical Department (Johnson Matthey Technology Centre (JMTC), Sonning Common, UK); Junwang Tang (University College London, UK); David Sarphie, Sanjay Santhasivam and Ainara Garcia Gallastegui (Bio Nano Consulting, UK) for valuable discussions and experimental assistance; Andrew Cakebread (King’s College London, UK) for ICP analysis; Zlatko Saracevic (Department of Chemical Engineering and Biotechnology, University of Cambridge, UK) for BET measurements; and the Deanship of Scientific Research at King Abdulaziz University, Saudi Arabia, for the support of this project (T/80/429).

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The Authors

Irene Paulauskas is a Materials Science Engineer with a PhD obtained from the University of Tennessee, USA. She has experience in the development, evaluation and characterisation of alloys and semiconductors for a variety of green energy applications such as fuel cell components, hydrogen generation and water purification.

Deena Modeshia’s research interests are focused on the synthesis of oxide materials as depollution catalysts and for water purification. These are synthesised via a CVD or solvothermal route to form pgm doped oxides both in situ and ex situ. Other interests include the inclusion of ceria into a titanate pyrochlore structure to increase the efficiency of the material for use as a catalyst in both solid oxide fuel cells and low temperature water-gas shift catalysis.

Tarek Ali’s research interests include acid-base catalysis, oxidation catalysts, photocatalysis, supported metal catalysts and the preparation of nanocomposite materials by novel methods. He is currently Assistant Professor of Physical Chemistry at King Abdulaziz University, Saudi Arabia.

Professor Elsayed El-Mossalamy investigates the synthesis, characterisation and applications of experimental charge transfer complexes in organic and inorganic materials, nanoparticles and nanocomposites. More recently his work has focused on the study of optical and electrical properties of nanomaterials.

Professor Abdullah Obaid is a Professor of Physical Chemistry at King Abdulaziz University. His main research interest is in the field of thermal analysis and physicochemical characterisation of inorganic and organic materials. He has also worked on the synthesis and characterisation of platinum-doped and undoped titanium dioxide catalysts.

Professor Sulaiman Basahel is a Professor of Physical Chemistry at King Abdulaziz University. His research interests cover heterogeneous catalysis, nanomaterials, advanced materials, nanoparticles and the synthesis and characterisation of metal oxide-supported platinum catalysts.

Felicity Sartain is a Chemist with Bio Nano Consulting, UK, whose current research interests are in the development and implementation of nanocatalysts for cleantech applications, specifically carbon capture and water purification.

Professor Ahmed Al-Ghamdi is a Professor of Solid State Physics at King Abdulaziz University. His research interests lie in the preparation, characterisation and application of bulk and thin film organic and inorganic materials in the solid state. He has been working on nanocomposites for eight years, and is now working on the development of optical and electrical devices utilising semiconductor nanomaterials.



“Design and Applications of Single-Site Heterogeneous Catalysts: Contributions to Green Chemistry, Clean Technology and Sustainability”By Sir John Meurig Thomas (University of Cambridge, UK), Imperial College Press, London, UK, 2012, 293 pages, ISBN: 978-1-84816-909-8 (Hardcover), £79.00, ISBN: 978-84816-910-4 (Softcover), £38.00


Reviewed by Richard Wells* and Alan McCue**

School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Meston Walk, Aberdeen AB24 3UE, UK

Email: *[email protected]; **[email protected]

IntroductionIn 2010 Sir John Meurig Thomas was awarded the

Gerhard Ertl Lecture award by the Max Planck

Institutes of Berlin. As a result of the lecture he has

subsequently written the book entitled “Design and

Applications of Single-Site Heterogeneous Catalysts:

Contributions to Green Chemistry, Clean Technology

and Sustainability”. The work is as expected rather

eloquently written by a leader in the fi eld and

successfully attempts to summarise the huge volume

of work published over the last decades. The book is

split into three sections: fi rstly the reader is introduced

to the concept of single-site heterogeneous catalysis

with emphasis placed on the difference between

materials such as aluminosilicates and immobilised

homogeneous catalysts and the similarities between

single-site heterogeneous catalysts and enzymes. The

second and third sections are then divided between

the use of microporous and mesoporous materials

as single-site heterogeneous catalysts and how such

materials can be used to eradicate the need for

either hazardous or stoichiometric reagents. There

are numerous examples of high quality work utilising

single-site materials to modernise and improve the

green credentials of reactions of industrial and

academic interest, and two chapters deal with catalysis

involving platinum group metals (pgms).

Catalyst DesignChapter 7 discusses the possibilities of exploiting

the space contained within nano sized pores for

asymmetric reactions, with palladium and rhodium

often being the metals of choice. It has been shown

that the enantioselectivity of such metal complexes can

be enhanced when confi ned within pores of a similar



size to that of the complex and this raises interesting

questions which should be considered during catalyst

design. For example, can the enantioselectivity of

a reaction be routinely improved beyond what is

achievable under homogeneous conditions by the

selection of a material with appropriately sized pores?

The text describes a particularly striking example

where the enantioselectivity of a rhodium-based

complex increases from less than 20% to greater than

95%, for the asymmetric hydrogenation of methyl

benzoylformate to methyl mandelate, by immobilising

the complex in a suitably sized porous silica. However,

whilst benefi cial effects in terms of enantioselectivity

may be observed, one must also consider what

effect the support of choice will have on complex

accessibility/activity.

The pgms feature more heavily in Chapter 8 under

the title of ‘Multinuclear, Bimetallic Nanocluster

Catalysts’. Here the author describes some of the

benefi ts which can be obtained from using clusters

such as Ru6Pd6 supported on mesoporous silica. Such

a cluster has been shown to be more active (by an

order of magnitude) compared with a nanoparticle

equivalent for the hydrogenation of 1-hexene. In

addition, changing from a bimetallic cluster (Ru6Pd6)

to a monometallic cluster (Ru6) results in the reaction

selectivity changing from favouring hydrogenation

to isomerisation. A variety of other bimetallic

(ruthenium-tin, ruthenium-platinum, ruthenium-

copper and rhodium-tin) and trimetallic (ruthenium-

platinum-tin and ruthenium-platinum-germanium)

pgm-containing clusters are also discussed.

ConclusionThis well-written book is a thoroughly enjoyable read at

a reasonable price. It comes highly recommended for

anyone with an interest in single-site heterogeneous

catalysts and would serve as a helpful and stimulating

introduction to someone new to the fi eld.

The ReviewersDr Richard Wells is a Senior Lecturer in the Department of Chemistry at the University of Aberdeen, UK. His research interests range across surface chemistry and heterogeneous catalysis, with particular emphasis on hydrogenation and enantioselective reactions.

Dr Alan McCue is currently a Research Fellow within the Department of Chemistry at the University of Aberdeen, UK. His research interests include the use of both traditional supported metal catalysts and single-site heterogeneous catalysts and how the selectivity of such systems can be manipulated.

“Design and Applications of Single-Site Heterogeneous Catalysts: Contributions to Green Chemistry, Clean Technology and Sustainability”



IX International Conference on Mechanisms of Catalytic ReactionsUnderstanding of platinum group metal catalysts essential for new fuels and reactions


Reviewed by Fiona-Mairéad McKenna

Johnson Matthey Technology Centre, Blount’s Court, Sonning Common, Reading RG4 9NH, UK

Email: [email protected]

The IX International Conference on Mechanisms of

Catalytic Reactions was held in Saint Petersburg, Russia,

from 22nd–25th October 2012 and was organised

by the Boreskov Institute of Catalysis (BIC), one of

the world’s largest research centres specialising in

catalysis. The Institute has been carrying out research

into the understanding and elucidation of the most

fundamental aspects of catalysis since 1958 and is

currently headed by Professor Valentin N. Parmon.

230 participants, predominantly from academic

institutions in 30 countries, applied to attend the

conference. Topics included:

(a) Catalysis from First Principles;

(b) Mechanisms of Heterogeneous Catalysis;

(c) Mechanisms of Homogeneous Catalysis;

(d) Catalytic Processing of Renewables;

(e) Electrocatalysis, Photocatalysis, Biocatalysis.

The conference included fi ve plenary lectures,

nine keynote lectures, 79 oral presentations and 110

posters. The meeting is held every three years. This is

the second time the conference’s offi cial language

has been English, prior to that it had been exclusively

in the Russian language. With the change from

Russian to English the meeting now inevitably attracts

signifi cantly more international interest and this is

expected to increase by the time of the next meeting

in 2015. Renowned names from the world of catalysis

such as Alexis T. Bell (University of California, Berkeley,

USA), Notker Rösch (Technical University, Munich,

Germany), Robert Schlögl (Fritz-Haber Institute of the

Max Planck Society, Berlin, Germany), Bert Weckhuysen

(Netherlands Institute for Catalysis Research, Utretcht,

The Netherlands) and Rutger Van Santen (Eindhoven

University of Technology, The Netherlands) all took

part in the organisation of the conference.

This review will discuss the presentations made in

terms of those subjects which attracted the greatest

attention and are of interest to the platinum group

metals (pgms). Other topics including photocatalysis

and biomass reforming were also discussed at the

meeting; however they go beyond the scope of this

review.



Methane OxidationGiven the abundant resources of methane worldwide

there was understandably a signifi cant focus on the

possible uses and clean combustion of this carbon-

effi cient fuel. Methane has the lowest carbon-to-

hydrogen ratio of any fossil fuel, and its combustion

demonstrates the smallest carbon footprint-to-energy

ratio. For this reason there is already widespread use

of compressed natural gas (CNG) vehicles worldwide.

In North America particularly, the fuel is attractive due

to its low cost of around US$3/MMBtu (million British

thermal units, approximately 1.05 GJ). In EU countries,

the price is over three times higher at around US$10/

MMBtu, while in Asian countries it is in the US$13–

US$15/MMBtu range. Representatives from Shell

Global Solutions recently stated (1) that developments

in ‘small scale’ liquid natural gas (LNG)/CNG facilities

are very important for mobile applications including

marine systems which are soon to be subject to

emission legislation.

Methane absorbs infrared signifi cantly more

strongly than does carbon dioxide, and it is therefore

a potent greenhouse gas. Emission of unused CH4

from LNG/CNG vehicle exhausts must therefore be

reduced by use of catalytic converters just as is the

case for gasoline or diesel fuelled cars. However,

methane is more diffi cult to oxidise than the majority

of other hydrocarbon species. Its strong C–H bond

is diffi cult to break catalytically, and consequently it

has a high light-off temperature, with typical values of

at least 400ºC. Palladium is the most active metal for

C–H bond activation and typically high loadings are

required. However, high levels of sulfur species and

water vapour are typically found in these systems, so

modifi ers are required to stabilise the activity of the

metal over a signifi cant catalyst lifetime. Alexander

Konstantinovich Khudorozhkov (Boreskov Institute of

Catalysis SB RAS, Novosibirsk, Russia) demonstrated

that the addition of nickel, cobalt or platinum to a

palladium/alumina catalyst stabilised its performance

in a ‘realistic’ automotive gas stream; however Pt was

only required in a concentration of 0.2% compared

to a requirement of 5% for the other metals. The

modifi ers were also found to improve activity at lower

temperatures compared to the monometallic catalyst.

The nature of the Pd precursor was also found to

affect stability, with the nitrate prepared catalyst being

initially less active than the acetate prepared catalyst

but demonstrating improved stability over time. It was

shown by X-ray photoelectron spectroscopy (XPS)

that deactivation by water was due to oxidation of the

Pd metal, implying that a more stable metallic phase

was formed from the nitrate precursor.

Platinum catalysts may also be used for low-

temperature CH4 combustion, although they deactivate

very quickly in excess oxygen due to the formation

of platinum oxide. It was demonstrated by Ilya

Pakharukov (Novosibirsk State University, Russia) that

the Pt system demonstrates hysteresis when increasing

and decreasing the Pt:O2 ratio. By this technique the

activity could be improved from 11% conversion to

80% under the same external conditions, suggesting an

interesting way to improve activity without modifying

the catalyst composition. However, under the higher

catalyst activity regime, selectivity was sacrifi ced

leading to signifi cant production of carbon monoxide

and hydrogen gas as well as carbon dioxide and water

vapour. Production of CO would subsequently require

a further downstream oxidation catalyst.

Platinum-ruthenium and nickel-copper-chromium

catalysts for methane oxidation were presented

by Kusman Dossumov (Institute of Combustion

Problems, Al-Farabi Kazakh National University, Almaty,

Kazakhstan) and although no comparison was made

to Pd catalysts it was suggested that the bimetallic

catalysts facilitated the reaction due to the presence

of distinct active centres in the same cluster, i.e. CH4

activation on Pt(0) or Ni(0) and O2 activation on

Ru(0) or Cu(0). It was clear from these studies that

the challenge of effi cient methane oxidation remains

great. Highly stable metallic alloys are required

to facilitate methane combustion and, at present,

high loadings of pgms are necessary for C–H bond

activation. Signifi cant improvements will be required

if the increase in natural gas use is continued.

There is increasing interest in using methane more

effi ciently for heating purposes in domestic and larger

boiler systems. Simple combustion of CH4 leads to CO,

H2 and NOx pollutants being formed from incomplete

combustion. Catalytic combustion in air can lead

to improved selectivity to CO2 and H2O with lower

formation of NOx as the reaction can take place at

temperatures at least 100ºC lower than traditional

combustion. Several factors must be optimised in order

to develop a feasible catalyst for this system which

would survive the lifetime of the boiler. Natural gas is

denatured with sulfur compounds which inevitably

make it diffi cult to develop a stable catalyst. Stefania

Specchia (Politecnico di Torino, Turin, Italy) presented

results based on a Pd/BaCeO3∙2ZrO2 catalyst prepared

by solution combustion synthesis starting from metal

nitrate/glycine mixtures which resulted in a spongy,



foamy textured material. A simulated sulfur ageing

was carried out for up to 450 h under hydrothermal

conditions at 800ºC under a fl ow of 9% CO2, 18% H2O

and 2% O2 in N2, including 200 parts per million by

volume (ppmv) of SO2 to emphasise any poisoning

effect. This accelerated ageing was said to simulate

two years of realistic boiler lifetime. After 150 h ageing

the temperature for 50% combustion (T50) of methane

had shifted upwards by approximately 100ºC relative

to the fresh catalyst; however after 300 h ageing the

light-off activity had improved by more than 60ºC

relative to the fresh catalyst (Figure 1) (2). This

improvement was explained by the decomposition of

the cerium-zirconium mixed oxide into its respective

separate oxides under the action of sulfation,

subsequently providing enhanced low-temperature

oxidation activity. A similar effect was observed with

a manganese-cerium-zirconium mixed oxide and

was explained in the same way. This effect was not

sustained and after the full 450 h ageing the catalyst

had lost all useful activity for methane combustion

and could not be regenerated.

Automotive CatalysisEmrah Özensoy (Bilkent University, Turkey) presented

a keynote lecture based on his research group’s

study of lean NOx trap (LNT) model systems using

a combination of spectroscopic techniques (3). The

presentation covered several aspects of traditional

LNT components, including barium dispersion and

its effect on reaction intermediates and the effect of

titania on the sulfur tolerance of the overall system.

The studies primarily used single crystal Pt(111)

as a support surface and barium oxide and/or TiO2

were deposited thereon. In relation to Ba dispersion,

NOx temperature programmed desorption (TPD)

was carried out following prolonged exposure to NO2

(Figure 2) (3). It was observed that there was distinct

variation in the NOx desorption profi les depending on

whether Ba existed as isolated islands with exposed Pt

sites or as an overlayer on the Pt surface. In the former

case, NO desorption occured at temperatures at least

60ºC lower than were observed for the overlayer

scenario. The temperature of desorption decreased

with decreasing Ba loadings, implying that NOx

desorption was facilitated by either increasing the

exposed Pt area or reducing the Ba particle size. There

was evidence of a barium peroxide species in both

cases however, which in the overlayer case appeared

to be formed via the decomposition of NO32– into

NO2 and O2–. In contrast this species appeared to be

permanently present on the isolated Ba islands system.

The effect of peroxides on catalyst performance was

not discussed.

The TiO2 modifi ed supports demonstrated an overall

greater resistance to sulfate formation on the surface of

the catalysts, as evidenced by infrared (IR) spectroscopy;

however the NOx uptake capacity was compromised

by barium titanate formation. XPS evidenced that the

surface Ba:Ti atomic ratio continually decreased with

increasing temperature, indicating the diffusion of Ba

beneath the surface. When an Al2O3 crystal surface

was modifi ed with TiO2 and subsequently Ba, it was

observed that the Ba dispersion correlated with that

CH4

conv

ersi

on, %

100

90

80

70

60

50

40

30

20

10

0250 350 450 550 650 750 850

Temperature, ºC

A, aA, bA, cB, aB, bB, cC, aC, bC, c

Fig. 1. Catalytic activity towards CH4 combustion of fresh and aged PdOx-based catalysts: A = 2%Pd/CeO2·2ZrO2; B = 2%Pd/LaMnO3·2ZrO2; C = 2%Pd/BaCeO3·ZrO2; a = fresh samples; b = 1 week aged samples; c = 2 weeks aged samples (2)



of the TiO2 particles. Well dispersed small particles of

TiO2 encouraged the formation of the same type of

BaO particles. Such correlation could prove useful to

serve as a templating tool for the Ba species on the

surface of alumina and perhaps other supports.

Mikhail Sergeevich Gavrilov (Boreskov Institute)

presented his studies on Pd-Rh/Al2O3 systems with the

aim of improving the fundamental understanding of

deactivation in three-way catalysts. The group have led

the way in the use of an analytical technique called

laser induced luminescence (LIL) for catalysis for

many years with several respected publications on

the subject (4, 5). Using this technique they showed

that at temperatures above 800ºC, Rh3+ diffusion into

bulk Al2O3 occurs in these alloys, accelerating the

conversion of the to the phase where the rhodium

is permanently encapsulated. The effect of the Pd:Rh

ratio was studied and it was shown that a 4:1 Pd:Rh

ratio resulted in a sharp decrease in the encapsulation

of the Rh3+ ions and hence signifi cantly greater stability.

Evgeny Ivanovich Vovk (Boreskov Institute

and Bilkent University) presented the results of a

collaboration between the LNT group in Bilkent and

the Boreskov Institute. The investigation focused on

the effect of adding ceria to Ba/Al2O3 LNT components.

A strong Pt-Ce interaction was evidenced by Raman

spectroscopy demonstrating the formation of Pt-O-Ce

bonds during calcination. It was this interaction which

was deemed responsible for the enhanced dispersion

and thermal stability of the Pt nanoparticles. NOx

reduction with H2 was monitored by IR spectroscopy

and it was shown that during reduction bridging

nitrates were partially converted to monodentate

nitrates, with subsequent formation of nitrites. A

mechanism for facilitated NOx reduction with H2 via

these Pt-O-Ce sites was also proposed (Figure 3).

400 600 800 1000Temperature, K

QM

S in

tens

ity, a

rbitr

ary

units

Incr

easi

ng B

aOx c

over

age

BaOx (≥ 2.5 MLE)/Pt(111)

BaOx (≤ 1 MLE)/Pt(111)

Clean Pt(111)

2E-7 640660

700

670

415 460

375

325

(BaOx)

10 MLE

5.5 MLE

2.5 MLE

1.0 MLE

0.8 MLE

0.5 MLEPt(111)

2

Fig. 2. NO (m/z = 30) channel of the TPD spectra obtained after saturation of the BaOx/Pt(111) surface having different BaOx surface coverages with NO2 exposure at 323K. QMS = quadruple mass spectrometry; MLE = monolayer equivalent (Reprinted with permission from (3). Copyright 2011 American Chemical Society)

Ce O Pt

H H

NO

O

O

Ce * PtOH

NO

O

O

NO O

Ce O PtOH

Fig. 3. Schematic representation of the route towards nitrite formation via the oxygen vacancy created in Pt-O-Ce bonds during NOx reduction with H2



This suggested that the oxygen vacancies formed

between the Pt-Ce centres greatly decreased the

barrier for nitrite formation and hence NOx reduction.

These results suggest that further investigations with

in situ Raman spectroscopy may be able to show the

disturbance of this Pt-O-Ce bond during reduction and

the presence of the nitrite, although no mention was

made of this possibility. The authors also concluded

that ceria had no effect on total NOx uptake of the

material when supported on Al2O3.

Surface Science and ModellingIn mechanistic discussions there is always a

signifi cant contribution from model surfaces and

computationally simulated reactions and hence there

is often a concern over the ‘material gap’ in going from

these systems to ‘real’ catalysts. Konstantin M. Neyman

(Institució Catalana de Recerca i Estudis Avancats

(ICREA), Barcelona, Spain) presented a keynote

lecture focused on surface science studies carried

out on single crystal surfaces rather than model

nanoparticles. He explained that in some reactions

the performance of a Pt(111) slab was more different

to that of a Pt79 (79 atom cluster) nanoparticle than

Pt would be to Ni. In this sense he cast signifi cant

doubt on the application of data obtained from single

crystal models to real systems. In particular, where

the formation of subsurface carbon or hydrogen is

fundamental to the mechanism, such as during olefi n

hydrogenation on Pd, it was shown that a model cluster

correctly simulates the fl exibility of the surface atoms

on a real system whereas the expansion of a Pd(111)

model would be severely restricted and therefore a

very different mechanism would be indicated. Likewise

the CO oxidation activity of ceria nanoparticles can be

up to twice that of bulk ceria and this was attributed to

the fact that the energy required for oxygen vacancy

formation depends on particle size, suggesting that

several different atom cluster sizes must be considered

in order to obtain ‘real’ information. It was further

shown that the presence of Pt facilitates the creation of

Ce3+ centres due to spillover of oxygen to the pgm and

this effect is enhanced with increasing temperature.

A keynote lecture presented by Günther Rupprechter

(Institute of Materials Chemistry, Vienna University of

Technology, Austria) demonstrated that, with careful

consideration and complementary information such

as in situ spectroscopy and surface microscopy,

simulated systems can be made to represent the ‘true’

situation in fi ne detail. In particular he described

the use of Pd-Zn alloys in direct methanol fuel cells

to produce CO2 and H2. Cu/ZnO catalysts have

been used for this reaction but deteriorate badly

over time. Pd-Zn nanoparticles supported on ZnO

offer the advantage of higher thermal and chemical

stability than their Cu counterparts, giving rise to

better long-term stability and less deactivation with

time-on-stream. It has been shown that a Pd-Zn alloy

at the surface is required for high selectivity and

turnover frequency (TOF) but it was observed that

on calcination above 600K, Zn diffuses into the bulk

and the selectivity is lost. Rupprechter’s group used

low-energy ion scattering (LEIS) to investigate just the

top layer and showed that during this diffusion, the

surface alloy is maintained, but it is not suffi cient by

itself to provide the required selectivity. Subsequently

it was determined that multilayers of Pd-Zn alloy are

needed. Complimentary XPS data showed that the

valence band of Pd is not changed signifi cantly when

Zn is only present in the top layer. With thicker layers,

the Pd3d band shifts and then H2O can be activated,

facilitating selective conversion of MeOH to CO2 and

H2 (Figure 4) (6).

ConclusionsThe conference, as the name suggests, presented

detailed understandings of several systems and

elucidated the fact that with proper mechanistic

considerations it is possible to tune pgm catalysts so

that long-term stability and selectivity can be achieved

and in most cases, supersede those of cheaper, less

active alternatives. There is signifi cant scope for

increased demand for pgm catalysts with inevitably

changing fuel trends. More effi cient gasoline and

diesel engines require better low-temperature catalyst

performance which is diffi cult to accomplish with

base metals. The use of methane in engines or boilers

CH2O OH CH2O

Pd

O CH H

OH

Zn

OC

HH

Fig. 4. (a) p(2 × 1) surface structure of the 1:1 multilayer Pd-Zn alloy on Pd(111); (b) side view of the multilayer Pd-Zn alloy with likely surface intermediates reacting toward CO2 (6)



as well as methanol in fuel cells creates an even greater

demand for highly active catalysts which can perform

the demanding C–H bond breakage step. Likewise,

to produce on-board H2 for fuel cells via reforming,

catalysts with good low-temperature activity and

stability are paramount, and it was shown by many of

the presenters at this conference that issues regarding

pgm use in these systems can be overcome with better

comprehension, such as that achieved for the Pd-Zn

system.

As model systems become more widely used and

advanced, the data which arise appear more and

more relevant to ‘real’ systems. The use of in situ

spectroscopy cannot be disputed as an invaluable

tool in identifying the crucial sites required for

reactions to proceed. There is even scope to extend

the already expansive spectroscopy tools commonly

used, as demonstrated by the group at the Boreskov

Institute who are leading the way in the less well-

known laser induced luminescence technique.

This appears to be particularly useful in elucidating

ageing mechanisms, even with pgm loadings as low

as 0.03%.

The organising committee did a fantastic job in

providing high quality presentations from worldwide

institutions but it cannot be ignored how much

extraordinary research is coming from the Boreskov

Institute directly on a wide variety of topics. The next

conference in this series will take place in 2015.

References 1 W. Warnecke, ‘Automotive Fuels – The Challenge for

Sustainable Mobility’, 2012 Directions in Engine-Effi ciency and Emissions Research (DEER) Conference, Dearborn, Michigan, USA, 15th–19th October, 2012

2 S. Specchia, P. Palmisano, E. Finocchio and G. Busca, Chem. Eng. Sci., 2010, 65, (1), 186

3 E. I. Vovk, E. Emmez, M. Erbudak, V. I. Bukhtiyarov and E. Ozensoy, J. Phys. Chem. C., 2011, 115, (49), 24256

4 A. A. Vedyagin, A. M. Volodin, V. O. Stoyanovskii, I. V. Mishakov, D. A. Medvedev and A. S. Noskov, Appl. Catal. B.: Environ., 2011, 103, (3–4), 397

5 V. O. Stoyanovskii, A. A. Vedyagin, G. I. Aleshina, A. M. Volodin and A. S. Noskov, Appl. Catal. B.: Environ., 2009, 90, (1–2), 141

6 C. Rameshan, C. Weilach, W. Stadlmayr, S. Penner, H. Lorenz, M. Hävecker, R. Blume, T. Rocha, D. Teschner, A. Knop-Gericke, R. Schlögl, D. Zemlyanov, N. Memmel, G. Rupprechter and B. Klötzer, J. Catal., 2010, 276, (1), 101

The Reviewer Fiona-Mairéad McKenna studied Physics and Chemistry of Advanced Materials in Trinity College Dublin, Ireland, and went on to obtain a PhD from the University of Aberdeen, UK, on the topic of acetylene hydrogenation over Pd/TiO2 catalysts. Following a brief period using radio plasmas to deposit hydrophobic layers on carbon fi bres, she moved to England to take up a position in the Emission Control Research group at Johnson Matthey Technology Centre, Sonning Common, UK. She is now a Senior Scientist working on pgm-based lean NOx traps.



“PEM Fuel Cells with Bio-Ethanol Processor Systems: A Multidisciplinary Study of Modelling, Simulation, Fault Diagnosis and Advanced Control”Edited by M. S. Basualdo (CAPEG-CIFASIS-(CONICET-UNR-UPCAM) and UTN-FRRo, Argentina), D. Feroldi (CAPEG-CIFASIS-(CONICET-UNR-UPCAM) and DCC-FCEIA-UNR, Argentina) and R. Outbib (LSIS-Domaine Universitaire de Saint-Jérôme, Marseille, France), Green Energy and Technology, Springer-Verlag, London, UK, 2012, 461 pages, ISBN: 978-1-84996-183-7, £117.00, €139.05, US$179.00


Reviewed by Laura Calvillo

School of Chemistry, University of Southampton, Highfi eld, Southampton SO17 1BJ, UK


Introduction“PEM Fuel Cells with Bio-Ethanol Processor Systems”,

edited by Marta S. Basualdo and Diego Feroldi

(French-Argentine International Center of Information

and Systems Sciences, Argentina) and Rachid

Outbib (LSIS-Domaine Universitaire de Saint-Jérôme,

Marseille, France), who are experts in simulation,

control and fault detection of large systems, is part

of the series Green Energy and Technology. This

book presents some typical problems encountered

in proton exchange membrane fuel cell (PEMFC)

systems and proposes alternative ways of operation

using conventional and advanced control techniques.

The book is divided into two main parts. The fi rst

part consists of eight chapters and is dedicated to

fuel cell systems in terms of modelling, simulation,

advanced control and diagnosis; the second part

consists of six chapters and deals with fuel processor

systems for the production of hydrogen from bio-

ethanol. The writing style is clear and the authors give

a detailed description of the systems and processes

at the beginning of each chapter, which allows even

the non-specialist reader to easily follow the concepts

under discussion. However, in some of the chapters,

prior knowledge of the specifi c software packages

used is needed.

Part I: PEM Fuel Cells: Modeling, Simulation, Advanced Control and DiagnosisFuel Cell Systems: Concepts and DescriptionThe book opens with two chapters in which the

authors introduce the fuel cell systems and the main



concepts discussed in the book. Chapter 1 by Diego

Feroldi et al. starts by describing a fuel cell and its main

applications, and includes the main characteristics of

the different types of fuel cell technologies, covering

important terms such as effi ciency, operation and

working temperature. Subsequently, the concept of

control and diagnosis of PEMFC systems is introduced

and the main challenges related to this control are

described. Later, the authors deal with fuel cell hybrid

systems (FCHSs), showing their advantages and

methods for energy management. Finally, the problems

related to hydrogen production and storage are

commented on and different methods for producing

hydrogen are described, focusing on processor

systems for bio-ethanol, which are the subject of the

second part of the book.

Chapter 2 by Diego Feroldi and Marta Basualdo,

however, is focused on PEMFC systems, whose main

components are the feeding channels, diffusion layer,

and catalytic layer in both the anode and cathode, and

the membrane. The unit formed by the catalytic layer

and the membrane is called the membrane electrode

assembly (MEA) and is the heart of the system. The

electrocatalyst materials used in these systems are

based on platinum nanoparticles dispersed on carbon

materials.

The advantages and disadvantages of this kind

of system are provided. The high effi ciency and low

operation temperature of PEMFC are some of their

advantages, whereas their cost and the production

cost of hydrogen are the main disadvantages. Then

different modelling approaches described in the

literature are presented, focusing on dynamic models.

Particularly, the model that is used in the rest of the

book to represent the system is described in detail.

This model is also used to study the optimal operation

conditions of a PEMFC system.

Simulation and Control StrategiesThe following two chapters cover different control

strategies for two of the main challenges in fuel

cell operation: oxygen fl ow in the cathode and

thermal behaviour. Chapter 3 by Diego Feroldi et al.

is dedicated to oxygen fl ow, which is one of the most

important factors in terms of system performance,

since compressor consumption is a major parasitic

power drain. For this purpose, two different advanced

control strategies were tested. First, a methodology

based on dynamic matrix control (DMC) was applied,

both in the stationary and the transient state, and it

was shown that the effi ciency of the system can be

improved by manipulating the valve that closes the

cathode air fl ow and by changing the stack voltage.

The simulation showed a good dynamic response.

The second methodology was based on adaptive

predictive control with robust fi lter (APCWRF). This

methodology successfully managed the requirements

of a PEM in different scenarios and working zones.

In Chapter 4, a new modelling approach for

describing and controlling the thermal behaviour

of a PEMFC, developed by Abdelkrim Salah et al.

(LSIS, Aix-Marseille University, France), is described.

The approach is based on parallel computing. The

performance of three different systems: unifi ed

parallel C (UPC), parallel virtual machine (PVM) and

message passing interface (MPI), are analysed by

considering the computation times and the speedup

of computation for each implementation. The

proposed nodal network simulation model allows the

cell temperature evolution to be observed with greater

precision and the heat sensitive regions to be rapidly

identifi ed. The MPI and UPC systems with this nodal

network gave the best performances, signifi cantly

improving the execution time.

In the second part of the chapter, it is fi rst shown

that the thermal aspect of PEMFC performance can be

described by a bilinear model. Then a strategy based

on feedback stabilisation is proposed to control the

thermal behaviour, proving that the system can be

made asymptotically stable for a desired temperature.

Fault DiagnosisChapter 5 by Andres Hernandez et al. (Escuela

Colombiana de Ingeniería Julio Garavito, Colombia)

is dedicated to the problem of fault diagnosis for

PEMFC, presenting two strategies, the fi rst based on

electrical equivalence and the second on a statistical

approach. Flooding failure is a particular focus of this

chapter. The fi rst strategy is based on the electrical

equivalent model and is shown to be effi cient in a

dynamic system. In addition, it has the advantage

that existing software for electrical network analysis

can be easily adapted. The results obtained by this

model are very promising for fuel cell fault diagnosis.

The second strategy is not based on any model but

on information from fuel cell conditions and cell

operation modes. This strategy was experimentally

tested for different operation modes, showing that



they can be characterised by cell voltage distributions

specifi c to each mode. It is then possible to identify the

cause of a fault by establishing a relationship between

the surface geometry of the voltage distribution and

the phenomena which produced the fault.

In Chapter 6, written by Diego Feroldi, a new

model-based fault diagnosis methodology for PEMFC

systems is presented and tested. This new diagnosis

methodology can correctly diagnose simulated

faults, giving better results than other well known

methodologies which use a binary signature matrix

of analytical residuals. The new methodology has

the advantage that it does not require knowledge of

the magnitude of the fault to provide a diagnostic.

In the second part of the chapter, this fault-tolerance

methodology is included in the model predictive

control (MPC) strategy, complementing Chapter 3.

This has never been addressed in the literature for fuel

cell systems before and constitutes one of the most

important contributions of this book.

Fuel Cell Hybrid SystemsThe next two chapters of the book are dedicated to

FCHS. They constitute a continuation of Chapters

3 and 6, coupling the fuel cell system (FCS) with

an energy storage system. First, Chapter 7 by Diego

Feroldi deals with the design and analysis of FCHS

oriented to automotive applications, comparing

the use of batteries and supercapacitors as energy

storage devices (Figure 1) and concluding that

supercapacitors seem to be the best alternative. The

main contributions of this chapter come from the

three different methodologies proposed to design and

analyse FCHS.

Then, in Chapter 8, energy management strategies

for this type of system are addressed by Diego

Feroldi. Three new strategies are proposed, two of

them based on the FCS efficiency map: operating

firstly in a zone where the efficiency is high and

secondly at its point of maximum efficiency.

The third strategy is based on using constrained

Battery FCHEV

Supercapacitor FCHEV

Fuel cell

Fuel cell

Fuel cell

Fuel cell

Fuel cell

Fuel cell

MotorGDU*

MotorGDU

MotorGDU

MotorGDU

Battery Battery BatteryDC/DC DC/DCDC/DC

MotorGDU

MotorGDU

Super-capacitor

Super-capacitor

Super-capacitor

*GDU = gear drive unit

Fig. 1. Operating modes of battery and supercapacitor fuel cell hybrid electric vehicles (FCHEVs) (Image courtesy of Tae Won Lim, Fuel Cell Vehicle Group, Hyundai Motor Company and Kia Motors Corporation, Korea)

Acceleration Normal driving Deceleration



nonlinear programming to minimise hydrogen

consumption. The author does a very good job of

testing the different strategies, first in a simulation

environment and then in an experimental setup,

showing that it is possible to achieve a good

reduction in hydrogen consumption.

Part II: PEM Fuel Cells in the Context of the Fuel Processor System with Bio-EthanolDesign and Control of the Bio-Ethanol Processor with PEMFCThe second part of the book opens with four chapters

(Chapters 9–12) dedicated to the design and control

of bio-ethanol processors. Though the book does

not mention pgm-based catalysts for this process,

some work has been done on platinum, palladium or

rhodium catalysts, among others (1–4). An extensive

review of the bio-ethanol processor system (BPS)

with PEMFC is given by Lucas Nieto Degliuomini

et al. (CAPEG-CIFASIS-(CONICET-UNR-UPCAM),

Argentina) in Chapter 9. A plant-wide heuristic control

procedure was applied, whose good results were

the basis for further investigations using a control-

oriented dynamic model, described in Chapter 10 by

Lucas Nieto Degliuomini et al. This model was used

to obtain good effi ciencies and to maximise heat

recovery, but it also allows other possible kinetics,

sizing of the system, etc. to be analysed.

Chapter 11 by Lucas Nieto Degliuomini et al.

constitutes a detailed guide for developing a

computational model of the BPS with PEMFC for

steady state and dynamic models. In this chapter,

the authors describe in great detail how to construct

the steady-state model of the BPS and then how to

move to a dynamic model step by step. All the units

used in the model are explained and the conditions

of each stream are justifi ed. For this purpose, matrix

laboratory (MATLAB), hypothetical system (system

hypothesis) (HYSYS) and advanced vehicle simulator

(ADVISOR) software packages were used. The reader

needs prior knowledge of these systems in order

to get the most out of the chapter. However, some

references for their use are recommended in the

text for those who are unfamiliar with the different

software packages.

In Chapter 12, written by Lucas Nieto Degliuomini

et al., the dynamic model described in Chapter 10 is

considered for simultaneously addressing the optimal

sensor network and plant-wide control structure for

BPS with PEMFC.

Fault DetectionThe last two chapters of the book are dedicated

to fault detection for the BPS with PEMFC. Due to

the complexity of the problem, the use of genetic

algorithms is needed. First, in Chapter 13, David

Zumoffen et al. (CAPEG-CIFASIS-(CONICET-UNR-

UPCAM) and FRRo-UTN, Argentina) integrate the

methodology used for fault detection into the model

for the optimal sensor network and control structure

selection described in Chapter 12. The authors show

that the detectability function can be calculated

based on the combined results of an optimal selection

of signals and, as consequence, a comparable or

even better detection performance can be obtained

to that derived from the complete set of signals. This

methodology has been tested on seven critical faults,

and constitutes a new strategy to solve problems in

process industries.

Subsequently, in Chapter 14, Estanislao Musulin

and Marta Basualdo (CAPEG-CIFASIS-(CONICET-

UNR-UPCAM) and DCC-FCEIA-UNR, Argentina) go

one step further and take into account time delays

in order to improve the model. For that purpose, a

genetic algorithm-based optimisation is presented

that improves the principal component analysis

methodology. The improvements of the model

proposed in Chapters 13 and 14 were successfully

tested, indicating that the new methodology is able

to give satisfactory fault detection especially for

systems in which safety aspects must be taken into

account.

ConclusionsThe authors state that the aim of the book is to present

useful tools for studying the entire system from

hydrogen production by bio-ethanol reforming to

power generation in the fuel cell stack. This objective

has been achieved in full, with the book presenting

the most challenging control problems in the fuel

cell system and proposing new ways of operation

using advanced control techniques. Some of the new

methodologies proposed in the book have never

before been addressed in the literature for this kind of

system, which makes the book much more interesting

and recommended.



The writing style is clear and all the concepts and

procedures are explained in detail, which allows

the reader to follow the book easily. However, the

reader is required to have a general understanding

of thermodynamics and, for some of the chapters, a

prior knowledge of MATLAB, HYSYS and ADVISOR

software.

Overall, the book covers a topic of much interest

for a wide audience, both for people involved in

academia, for teaching purposes in simulation and

control techniques, and for people working in industry

who are interested in applying the new methodologies

to their systems. The book’s authors have studied

PEMFC systems using different methodologies for

their control and fault diagnosis in order to improve

the operation of these systems, independently of the

catalysts that are used.

References1 M. K. Moharana, N. R. Peela, S. Khandekar and D.

Kunzru, Renew. Sustain. Energy Rev., 2011, 15, (1), 524

2 M. Koehle and A. Mhadeshwar, Chem. Eng. Sci., 2012, 78, 209

3 E. Gucciardi, V. Chiodo, S. Freni, S. Cavallaro, A. Galvagno and J. C. J. Bart, React. Kinet. Mech. Catal ., 2011, 104, (1), 75

4 R.-F. Horng, H.-M. Chou, W.-C. Chiu, J. A. L. Avalos, M.-P. Lai and Y.-M. Chang, Energy Procedia, 2012, 29, 216

The ReviewerLaura Calvillo was awarded her degree in Chemical Engineering from the University of Zaragoza, Spain, in 2004. She obtained a European PhD in Chemical Engineering from the same university in December 2008. In 2009 she moved to the University of La Laguna, Spain, with Professor Elena Pastor, and in 2010 she began work at the University of Southampton, UK, with Professor Andrea E. Russell where she was awarded a Marie Curie Intra-European Fellowship. Her work is focused on the study of new materials for fuel cells: new synthetic carbon supports and electrocatalysts based on platinum with different nanostructures.

“PEM Fuel Cells with Bio-Ethanol Processor Systems”

� •Platinum Metals Rev., 2013, 57,�(1),�57–65•


Phase Diagram of the Iridium-Rhenium System


by Kirill V. Yusenko

Department of Chemistry, Center for Materials Science and Nanotechnology, University of Oslo, PO Box 1033 Blindern, N-0315 Oslo, Norway


The experimental data on the binary metallic iridium-rhenium system available to date are inconsistent. The present work summarises recent experimental data on the Ir-Re system with the aim of allowing the correct solidus parts of the equilibrium phase diagram to be constructed. The examination of data obtained by different synthetic methods and thermodynamic calculations has revealed that the maximum solid-phase solubilities at 2000ºC of Re in Ir and Ir in Re are 20 at% and 68 at%, respectively. The binary phase diagram proposed in this paper serves as a reliable model for representing the available experimental data.

Polymetallic compositions containing platinum group metals (pgms) and rhenium have high hardness and high thermal stability, and are useful to industry in constructional, high-temperature and high-hardness materials and as components of superalloys (1). Iridium-rhenium solid solutions are used as the working elements of high-temperature thermocouples (2) and in high-temperature and chemically resistant materials for crucibles (3), while Ir/Re/Al2O3 and Ir/ReOx/SiO2 composites have been proposed as active heterogeneous catalysts (4, 5). It is well known that the properties of metallic solid solutions are affected by their composition and preparatory conditions, as well as the presence of impurities. The composition and temperature dependence of alloy properties is widely studied in order to analyse and predict the behaviour of metallic phases. However, difficulties in preparing solid solutions have led to poor and inconsistent information about the Ir-Re system and the corresponding physical properties of its metallic phases.

To investigate the chemical, physical and material properties of Ir-Re solid solutions, the construction of the correct equilibrium phase diagram is required. Prediction of ternary and quaternary phase diagrams is impossible without profound knowledge of two-component systems, so accurate data on the latter are essential. These systems are characterised by the extremely high melting points of their metal

A useful model of the available experimental data is presented



components, making the collection of such data difficult. To solve this problem, different research groups have used thermodynamic modelling as a reliable tool for understanding and predicting phase behaviour. Thermodynamic calculation of equilibrium phase diagrams gives information about possible solubility limits and peritectic temperature, and can be used for materials design and industrial process optimisation. For example, thermodynamic calculations using the CALPHAD method have been performed for different binary phase diagrams including platinum-ruthenium (6–8), rhenium-tantalum (9), rhenium-tungsten (9) and rhenium-rhodium (10), where the regular solution model was applied and showed a good agreement with available experimental data.

The present paper aims to critically analyse recent experimental data and thermodynamic calculations with the application of mixing parameters for solid

and liquid phases in the Ir-Re system and to construct a reliable model for further investigations of the phase behaviour in the system described.

The Iridium-Rhenium System: Experimental DataExperimental data on the Ir-Re system were obtained during the 1950s and 1960s using high-temperature melting and annealing of fine metallic powders in vacuum (11–13). A phase diagram was constructed based on the analyses of bimetallic solid solutions prepared at wide concentration intervals (14). As obtained, the peritectic phase diagram had three regions in the solid state: face-centred cubic (fcc) solid solutions in the Ir part, hexagonal close packed (hcp) solid solutions in the Re part and a broad two-phase region between the single-phase sections (Figure 1). The maximum solubilities of Re in Ir and Ir in Re at 1000ºC were estimated as 28 at% and

3000

2500

2000

1500

1000

5000 20 40 60 80 100

Ir Composition, at% Re Re

Tem

pera

ture

, ºC

Key

Experimental (14)

Kaufman (15)

Calc. ideal solution (this study)

Calc. thermo-dynamic data (20)

Calc. mixing parameter (this study)

fcc

hcp

Fig. 1. Phase diagram for the iridium-rhenium system: experimental (14); proposed by Kaufman (15); calculated using the ideal solution model for all phases; calculated using thermodynamic data for solid solutions 0 652 2 0 83L TIr

hcp,Re . .= − + and 0 1070 3 1 03L TIr

fcc,Re . .= − + (20); and calculated using also a liquid

mixing parameter of 0LIrliq,Re = 8000. Squares and hexagons correspond to fcc and hcp solid solutions with

the respective references. A two-phase sample with 25 at% Re is shown as a black circle. Compositions and preparatory temperatures are given according to Table I



39 at%, respectively, and the peritectic temperature was determined as 2800ºC. The corresponding tie-lines for the liquidus part of the diagram were not examined experimentally and have been drawn schematically between the invariant reaction line and the melting points of the pure metals. The purities of the initial Ir and Re powders used for the preparation of the solid solutions were not reported (11–13). As single-phase samples showed unreliable atomic volumes (12) some experimental data are likely to be incorrect.

Two-component phase diagrams for Re with all pgms were later calculated by Kaufman using the ideal solution model (15). The correctness of the model was confirmed by further measurements of mixing volumes and formation enthalpy. The calculated and experimentally obtained phase diagrams were adequate for the majority of metallic systems with the exception of Re-Rh and Ir-Re. The disagreements between theoretical calculations and earlier and more recent experimental data can be explained in terms of the incorrectness of the corresponding experimental diagram as it occurs for the Re-Rh system (10, 16). Therefore high precision experimental data are needed to help understand the equilibrium behaviour of the Re-Rh and Ir-Re systems.

Thermodynamic data (integral enthalpy, entropy and Gibbs free energy), which are available for pure Ir (17, 18) and Re (19) and also for a number of Ir-Re solid solutions (20), might be taken into account to precisely describe the phase equilibria. Thirteen solid solutions across the full range of concentrations were prepared and used to determine Gibbs formation energies as a function of temperature and concentration by the electromotive force method with a solid electrolyte (rhenium oxides and fluorides) (20). Data interpretation was partly based on a previously published phase diagram (14). The experimental data obtained in the ranges 0 at% to 20 at% Re (fcc region) and 60 at% to 100 at% Re (hcp region) could be used to estimate the mixing energies for Ir-Re solid solutions. The following mixing parameters for hcp and fcc solid solutions can be extracted from the data and used for further phase diagram calculation:

Single source precursors are widely used to prepare different oxide and metallic phases (21). This approach has also been applied to the preparation of Ir-Re solid solutions under mild conditions using bimetallic

double complex salts as precursors (22–25). For example, an Ir0.50Re0.50 solid solution can be obtained by thermal decomposition of [Ir(NH3)5Cl][ReCl6] in a hydrogen or argon stream at 600ºC. A variety of other precursors have been used to prepare a range of other solid solutions of differing compositions. As well as thermal decomposition of the individual double complex salts, Ir-Re metallic phases have also been prepared by thermolysis of their solid solutions (22). The isoformular compounds [Ir(NH3)5Cl]-[ReCl6] and [Ir(NH3)5Cl][IrCl6] are isostructural and their co-crystallisation gives the single-phase solid solution [Ir(NH3)5Cl][IrCl6]x[ReCl6]1–x. Thermal decomposition of the latter results in a metallic phase with the composition Ir0.5+0.5xRe0.5–0.5x. In the same manner, IrxRe1–x solid solutions can be prepared by thermal decomposition of the easily synthesised compound (NH4)2[IrCl6]x[ReCl6]1–x. This method allows a broad range of metallic compositions to be prepared and can also be applied to other systems such as Ir-Os (27) and Ir-Ru (28).

Recently, several Ir-Re solid solutions were prepared by high-pressure high-temperature annealing of metallic powders (29). To improve the solidus part of the diagram, the composition of the Ir-Re mixtures was selected from the two-phase region. High-pressure high-temperature annealing was chosen as a quick and reproducible method for preparation of metallic phases with extremely high melting points. Special boron nitride reactors with graphite covering were used to avoid the formation of oxides and nitrides.

All of the metallic phases described in the literature have been characterised using powder X-ray diffraction, elemental analysis and scanning electron microscopy, with lattice parameters and atomic volumes measured. The data for all single phases known in the literature are summarised in Table I. According to Zen’s law for hcp-fcc bimetallic systems, the atomic volumes V/Z (where V is the volume of the elemental cell and Z corresponds to the number of atoms in the elemental cell, with Z = 6 for hcp and Z = 4 for fcc) should display nearly linear dependence on composition with a relatively small positive or negative deviation (30, 31). For systems with phase separation, V/Z dependences need to be determined separately for each single-phase part of the phase diagram. Solid solutions in the Ir-Re system show a small negative deflection from linearity (<2%), which roughly reflects the idealness of the system (Figure 2). The corresponding V/Z dependence is described by the following second order polynomial functions:

(i)

(ii)

0

0

652 2 0 83

1070 3 1 03

L T

L T

Irhcp

Irfcc,Re

,Re

. .

. .

= − +

= − +



Tab

le I

Cry

stal

log

rap

hic

Dat

a o

n K

no

wn

Met

allic

Ph

ases

in t

he

Irid

ium

-Rh

eniu

m S

yste

m

Co

mp

osi

tio

nC

ell

par

amet

ers,

a, Å

c, Å

Cel

l p

aram

eter

s ra

tio

, c/a

Spac

e g

rou

pD

ensi

ty,

Dx,

g c

m–3

Ato

mic

vo

lum

e,V

/Z, Å

3

Prep

arat

ion

co

nd

itio

ns

Ref

eren

ce

Ir 3.

8399

8–

Fm3– m

22.5

614

.15

Mel

ting

poin

t 24

46ºC

(26,

No.

46-

1044

)

Ir 0.9

0Re 0

.10

3.84

2(2)

–Fm

3– m22

.44

14.1

8(2)

Ther

mal

dec

ompo

sitio

n in

H2

of [I

r(N

H3)

5Cl][

IrCl 6

] 0.8

[ReC

l 6] 0

.2 (7

00ºC

, 1 h

)(2

2)

Ir 0.8

5Re 0

.15

3.84

3(2)

–Fm

3– m22

.39

14.1

9(2)

Hig

h-pr

essu

re h

igh-

tem

pera

ture

ann

ealin

g

(200

0ºC,

4 G

Pa, 1

5 m

in)

(29)

Ir 0.8

0Re 0

.20

3.84

5(2)

–Fm

3– m22

.33

14.2

1(2)

Hig

h-pr

essu

re h

igh-

tem

pera

ture

ann

ealin

g

(200

0ºC,

4 G

pa, 5

min

)(2

9)

Ir 0.7

0Re 0

.30

2.73

6(2)

4.39

0(3)

1.60

5P6

3/m

mc

22.2

214

.23(

4)Th

erm

al d

ecom

posi

tion

in H

2

of

[Ir(

NH

3)5C

l][IrC

l 6] 0

.4[R

eCl 6

] 0.6

(700

ºC, 1

h)

(22)

Ir 0.6

0Re 0

.40

2.75

2(1)

4.37

1(2)

1.58

8P6

3/m

mc

22.0

014

.33(

4)H

igh-

pres

sure

hig

h-te

mpe

ratu

re a

nnea

ling

(2

000º

C, 4

Gpa

, 5 m

in)

(29)

Ir 0.5

0Re 0

.50

2.74

9(2)

4.37

1(3)

1.59

0P6

3/m

mc

21.9

714

.30(

4)Th

erm

al d

ecom

posi

tion

in H

2 of

[Ir(N

H3)

5Cl][

ReCl

6] (7

00ºC

, 1 h

)(2

2)

Ir 0.5

0Re 0

.50

2.74

3(2)

4.38

0(3)

1.59

7P6

3/m

mc

22.0

214

.27(

4)Th

erm

al d

ecom

posi

tion

in H

2 of

[Ir

(NH

3)5C

l][Re

Br6]

(700

ºC, 1

h)

(22)

Ir 0.4

0Re 0

.60

2.75

45(7

)4.

3739

(12)

1.58

8P6

3/m

mc

21.7

914

.37(

8)A

nnea

ling

in v

acuu

m (2

400º

C, 1

h)

(13)

Ir 0.3

3Re 0

.67

2.76

5(5)

4.38

3(6)

1.58

5P6

3/m

mc

21.5

914

.48(

8)Th

erm

al d

ecom

posi

tion

in H

2 of

[Ir(N

H3)

5Cl](

ReO

4)2

(600

ºC, 1

h)

(24)

(Con

tinue

d)



Tab

le I

(Co

nti

nu

ed)

Co

mp

osi

tio

nC

ell

par

amet

ers,

a, Å

c, Å

Cel

l p

aram

eter

s ra

tio

, c/a

Spac

e g

rou

pD

ensi

ty,

Dx,

g c

m–3

Ato

mic

vo

lum

e,V

/Z, Å

3

Prep

arat

ion

co

nd

itio

ns

Ref

eren

ce

Ir 0.3

0Re 0

.70

2.75

78(7

)4.

3865

(12)

1.59

1P6

3/m

mc

21.6

114

.45(

8)A

nnea

ling

in v

acuu

m (2

400º

C, 1

h)

(13)

Ir 0.2

5Re 0

.75

2.75

8(2)

4.39

3(3)

1.59

3P6

3/m

mc

21.5

514

.47(

4)Th

erm

al d

ecom

posi

tion

in H

e of

[Ir(N

H3)

5Cl] 2

[Re 6

S 8(C

N) 6

]⋅3H

2O (1

200º

C, 1

h)

(25)

Ir 0.2

5Re 0

.75

2.75

8(2)

4.39

4(3)

1.59

3P6

3/m

mc

21.5

414

.47(

4)Th

erm

al d

ecom

posi

tion

in H

2 of

(NH

4)2[

IrCl 6

] 0.2

5[Re

Cl6]

0.75

(100

0ºC,

1 h

)(2

3)

Ir 0.2

5Re 0

.75

2.75

8(2)

4.39

2(3)

1.59

2P6

3/m

mc

21.5

514

.47(

4)A

nnea

ling

in v

acuu

m o

f Ir 0

.25R

e 0.7

5 (8

00ºC

, 48

h)(2

3)

Ir 0.2

0Re 0

.80

2.76

08(7

)4.

4052

(12 )

1.59

6P6

3/m

mc

21.4

014

.54(

8)A

nnea

ling

in v

acuu

m (2

400º

C, 1

h)

(13)

Ir 0.1

0Re 0

.90

2.76

10(7

)4.

4314

(12)

1.60

5P6

3/m

mc

21.2

114

.63(

8)A

nnea

ling

in v

acuu

m (2

400º

C, 1

h)

(13)

Re

2.76

04.

458

1.61

5P6

3/m

mc

21.0

314

.71

Mel

ting

poin

t 31

80ºC

(26,

No.

5-7

02)



(V/Z)hcp = 14.20 – 0.16 × XRe + 0.53 × XRe2 (iii)

(V/Z)fcc = 14.15 + 0.17 × XRe + 0.82 × XRe2 (iv)

where XRe is the proportion of Re (at%) in the binary solid solution. The given functions can be used to estimate the composition of Ir-Re solid solutions with known lattice parameters.

The reported lattice parameters for Ir0.72Re0.28 (a = 3.65 Å, V/Z = 12.16 Å3) and Ir0.90Re0.10 (a = 3.76 Å, V/Z = 13.29 Å3) fcc solid solutions prepared by annealing of the pure metals at 2500ºC (12) seem to be incorrect, since the atomic volumes are less than the corresponding value for pure Ir. The reduced lattice parameters can be attributed to the formation of individual or mixed compounds of Ir and/or Re with light elements (primarily carbon, nitrogen and oxygen) as well as metallic impurities (mainly other light and heavy metals) in the initial Ir and Re powders. Therefore, these solid solutions are not taken into consideration in the present work.

Overall, it was found that phases prepared using different methods correspond to the same curves on the experimental phase diagram, showing that solid solutions obtained by thermal decomposition of single-source precursors or by high-temperature and high-pressure annealing are nearly equivalent and therefore both methods can be applied to the preparation of Ir-Re solid solutions. Heating the metallic solid solutions up to their melting points does not change the phase composition or lattice parameters, indicating that the phases are thermodynamically stable. The squares and hexagons in Figure 1 schematically show composition and preparatory temperatures for known single-phase Ir-Re solid solutions. Single-phase fcc solid solutions can be obtained up to 13 at% Re at 1200ºC, while the maximum concentration for hcp solid solutions was 25 at% Re (16, 32). The maximum solid phase solubility of Ir in Re is 68 at%, and that of Re in Ir is 20 at% at 2000ºC (29) which is comparable with the data obtained by Filatov (16, 32). This experimental

0 20 40 60 80 100

Ir Composition, at% Re Re

14.7

14.6

14.5

14.4

14.3

14.2

14.1

Ato

mic

vol

ume,

V/Z

, Å3

Key

fcc

hcp

Fig. 2. Atomic volumes for known fcc and hcp iridium-rhenium solid solutions with the corresponding references. Compositions and V/Z volumes are given according to Table I



data for solid solutions is inconsistent with the previously known phase diagram.

Theoretical CalculationsThe phase diagram for the Ir-Re system was calculated using the PANDAT 8 software (33) and the Scientific Group Thermodata Europe (SGTE) v. 4.4 thermodynamic database (34) in order to understand the inconsistency between the known phase diagram and the experimental data, and to help classify the available experimental data. Mixing energies used for the regular solution model calculated from the thermodynamic data obtained in (20) were compared with those obtained by calculation based on the ideal solution model.

Three calculated phase diagrams with different mixing parameters are shown in Figure 1. It can be seen that the calculated solid solubility limits are not in accordance with the existing experimental phase diagram (14). Nevertheless, there is good agreement between the solidus part of the theoretical phase diagrams and recently obtained experimental data for all single-phase Ir-Re solid solutions. The comparison clearly shows that the previously known experimental phase diagram for the Ir-Re system should be reconsidered and corrected for both the Ir (fcc solid solutions) and Re (hcp solid solutions) parts.

Calculations performed with or without the experimental thermodynamic data for Ir-Re solid solutions produce nearly identical results, which indicates that the mixing energies have little influence on the solid equilibria. Direct thermodynamic and equilibrium data for the liquidus part of the diagram are absent which makes it impossible to analyse the high-temperature part of the diagram. Diagrams calculated without mixing parameters or with mixing parameters only for the solid phases appear to be eutectic. The corresponding eutectic temperatures are 2436ºC (calculation using the ideal solution model for solid and liquid phases) and 2414ºC (calculation using mixing parameters for solid solutions only), which is close to the melting point of pure Ir (2446ºC) and shows a need for precise direct observation of the invariant reaction temperature. Optimisation of the 0LIr

liq,Re parameter for the liquid phase results

in a change in the invariant temperature without significant change in the two-phase field fcc+hcp. A positive value of 0LIr

liq,Re = 4000 results in a eutectic

temperature of 2465ºC. The peritectic temperature of 2512ºC can be obtained with 0LIr

liq,Re = 8000. Mixing

parameters 0LIr,Re for hcp and fcc solid solutions and

liquid phases are negative and relatively small which indicates nearly ideal behaviour of the Ir-Re system in both the solid and liquid parts.

Recommendations for Further WorkDespite the nearly ideal behaviour indicated above, further high precision thermodynamic and equilibrium data need to be included in the CALPHAD-based phase diagram optimisation to obtain better agreement between experimental and calculated data. Ab initio calculations would also improve our knowledge of the system discussed. The calculated fcc+hcp two-phase field below 1000ºC is broad and would also benefit from further improvement, since an hcp solid solution with a composition Ir0.7Re0.3 (22) was obtained in the two-phase region of the calculated phase diagram.

A critical analysis of all available experimental data on solid solutions of pgms and rhenium would enable a consistent database of thermodynamic data and phase diagrams for these systems to be constructed. This would also facilitate the prediction of the relevant ternary and quaternary phase diagrams. In addition, precise investigation of the physical properties of Ir-Re solid solutions such as hardness, electrical and thermal conductivity as well as thermoelectric characteristics and catalytic activity will improve the practical importance of the system discussed. Since not only Ir-Re but also oxide-containing compositions are of interest, the study of temperature, pressure and oxidation stability of metallic single- and poly-phase particles would also be beneficial.

The ordering in the Ir-Re system is still not understood and experimental investigation into the stability and properties of the intermetallic compounds will help reveal this. Nevertheless, four ordered phases: Ir8Re (Pt8Ti structure), Ir2Re (ZrSi2), IrRe (B19 structure designation) and IrRe3 (D019) – stable at zero temperature have been predicted using high-throughput ab initio calculation (35). Further modelling of the ordered phases at high temperature as well as calculation of temperature dependent thermodynamic functions will allow ordered phases to be included in the phase diagram calculation.

ConclusionsIn conclusion, the phase diagram proposed in this paper for the Ir-Re system serves as a reliable model for representing the experimental data available to date. Additional thermodynamic investigations especially on the melting of high purity metals will



further improve the liquid part of the phase diagram. The author believes that the data presented in this article will inspire further investigations on binary systems based on rhenium and the pgms, especially direct calorimetric and electrochemical examination of thermodynamic functions such as activity and mixing parameters for Ir-Re metallic solution in the solid and liquid states, which will in turn allow the practical usefulness of these alloys to be extended.

AcknowledgementsThe author is grateful to Dr Maria V. Yusenko (Westfälische Wilhelms-Universität Münster, Germany) for helpful discussions. The author would also like to thank the Referees for many helpful suggestions without which this paper would be much less complete.

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34 A. T. Dinsdale, CALPHAD, 1991, 15, (4), 317

35 O. Levy, M. Jahnátek, R. V. Chepulskii, G. L. W. Hart and S. Curtarolo, J. Am. Chem. Soc., 2011, 133, (1), 158



The AuthorKirill Yusenko studied chemistry at the Novosibirsk State University, Russia, and received his PhD in 2005 from the Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia, in the area of coordination and material chemistry of pgms. After a year as a postdoctoral researcher at the University of Hohenheim, Stuttgart, Germany, he spent three years as a researcher at the Ruhr-University Bochum, Germany, and one year as Laboratory Manager at solid-chem GmbH based in Bochum, Germany. Since 2012 he holds a position at the Department of Chemistry, University of Oslo, Norway. His scientific interests are focused on the chemistry of pgms and nanomaterials based on metallic particles, thin films and porous coordination polymers as well as solid-state chemistry of pharmaceutical materials.



“Fuel Cell Science and Engineering: Materials, Processes, Systems and Technology”Edited by Detlef Stolten and Bernd Emonts (Forschungszentrum Jülich GmbH, Germany), Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, Germany, 2012, 2 volume set, 1268 pages, ISBN: 978-3-527-33012-6, £270.00, €324.00, US$330.00


Reviewed by Brant Peppley

Queen’s-RMC Fuel Cell Research Centre, Innovation Park, Queen’s University, Kingston, Ontario K7L 3N6, Canada


Introduction“Fuel Cell Science and Engineering: Materials,

Processes, Systems and Technology” is a very

comprehensive review of the current status of this

technology. The book’s editors, Detlef Stolten and

Bernd Emonts of the Institute of Energy and Climate

Research at Forschungcentrum Jülich GmbH,

Germany, have a long history of working in the

fi eld of fuel cell research. Professor Detlef Stolten

is the Director of the Institute of Energy Research –

Fuel Cells at the Research Centre Jülich, Germany,

and received his doctorate from the University of

Technology at Clausthal, Germany. He served many

years as a Research Scientist in the laboratories of

Robert Bosch and Daimler Benz/Dornier. Professor

Stolten’s research focuses on electrochemical energy

engineering including electrochemistry and energy

process engineering of electrolysis, solid oxide fuel

cell (SOFC) and polymer electrolyte fuel cell (PEFC)

systems. Bernd Emonts is the Deputy Director of the

Institute of Energy Research at the Jülich Research

Centre, Germany. He was awarded his PhD on the

fundamentals of mechanical engineering from RWTH

Aachen University, Germany, in 1989. Emonts has been

involved in extensive research and development

projects in the areas of catalytic combustion and

energy systems with low-temperature fuel cells and

has published extensively in the fi eld of fuel cells.

The present book is divided into eight sections

that cover virtually all aspects of the current research

effort in fuel cells, beginning with reviews of the

various fuel cell technologies themselves, followed

by sections on materials and manufacturing issues,

diagnostics, quality assurance, modelling and

simulation, balance of plant design and components,

system demonstrations and market introduction, and

fi nally knowledge distribution and public awareness.



There are 71 contributing authors, 20 of these being

colleagues from the editors’ research centre at Jülich.

Other contributors include representatives from other

German laboratories, US Department of Energy (DOE)

laboratories, and a number of academic institutions

from the Western Hemisphere. There is however a

notable lack of contributions from Japan and Korea,

both key centres of hydrogen and fuel cell research.

Platinum Group Metal CatalystsPlatinum group metals (pgms) are mentioned

sporadically throughout the entire book. For example

platinum catalyst loadings are mentioned four times

in Chapter 1, ‘Technical Advancement of Fuel-Cell

Research and Development’ by Bernd Emonts and

colleagues. The fi rst mention is to inform the reader

that direct methanol fuel cells (DMFCs) have Pt catalyst

loadings of 4 to 16 mg cm–2. Later we are told that a

specifi c DMFC light traction vehicle (for example, a go-

cart) required >11 mg cm–2 and has been demonstrated

in Germany. On a more promising note, Daimler already

has, and General Motors (GM) aims to achieve by

2013, a per vehicle Pt catalyst requirement of 30 g. In

the conclusion of this chapter the minimum loading

for a DMFC of 4 mg cm–2 is deemed to be a signifi cant

barrier to commercialisation and the 30 g per vehicle

statistic is seen as being extremely promising.

The pgms are mentioned next in Chapter 4, ‘Alkaline

Fuel Cells’ by Erich Gülzow (German Aerospace

Center (DLR), Stuttgart, Germany), but only to say they

are good but that porous nickel can be used instead

of Pt for terrestrial applications. Pt, however, is the best

choice for use in space applications.

In Chapter 7 on ‘Micro-Reactors for Fuel Processing’

by Gunther Kolb (Institut für Mikrotechnik Mainz

GmbH (IMM), Germany), platinum and palladium are

both mentioned as alternatives to copper-zinc oxide

for methanol steam reforming. Several of the references

for this chapter deal with rhodium-based catalysts for

fuel processing but this pgm is not mentioned in the

text of the chapter.

In Chapter 8, on ‘Regenerative Fuel Cells’, by

Martin Müller (Forschungszentrum Jülich GmbH,

IEK-3, Germany) the catalysts for polymer electrolyte

membrane (PEM) electrolysers cover the entire span

of pgms. Pt is considered the best choice for hydrogen

evolution. For the oxygen evolution reaction the order

of catalytic activity is: iridium/ruthenium > iridium

> rhodium > platinum. For a unitised regenerative

polymer electrolyte membrane fuel cell (PEMFC) the

catalyst of choice for the oxygen electrode is a Pt/Ir

blend with Pt coated Ir oxide being mentioned as a

promising concept.

Platinum AlloysIn Chapter 14 on ‘Nanostructured Materials for Fuel

Cells’ by John F. Elter (Sustainable Systems LLC and

University of Albany, State University of New York, USA)

delves into the area of Pt alloys with discussion of

Pt-Ru, platinum-tin and platinum-cobalt. The classic

volcano plot showing that Pt provides a maximum

current density for the hydrogen evolution reaction

provides an interesting picture of how the pgms rate

for this benchmark electrochemical reaction. Later

in this chapter a very interesting fi gure is provided

showing how activity is infl uenced by the relationship

between oxygen binding energy and hydroxyl binding

energy (Figure 1) (1). This leads into a very interesting

discussion on Pt3M alloys, where M = nickel, cobalt,

iron, vanadium or titanium, that reviews the work of

Markovic and coworkers (2). This prefaces the perhaps

even more intriguing description of the core–shell

catalysts developed by Adzic and coworkers (3). The

shell is Pt on a Pd or Pd3Co core.

The discussion of pgms continues with a section

on the nanostructured thin fi lm (NSTF) electrode that

is being developed by 3M, who claim that they can

achieve a total pgm content of less than 0.18 mgPt kW–1

(this would be approximately 9 g of Pt for a 50 kW

automobile engine if it were a practical electrode).

Furthermore, 3M believe that they can meet the elusive

mass current density target set by the US DOE of

0.44 A mgPt–1 by using a Pt3Ni7 alloy. Other work being

done on using Pt-NSTFs on various oxide whisker

supports is also promising in terms of reducing catalyst

costs for PEMFCs.

Materials and ManufacturingChapter 15, ‘Catalysis in Low Temperature Fuel

Cells – an Overview’, by Sabine Schimpf and Michael

Bron (Martin-Luther-Universität, Halle-Wittenberg,

Germany), completes the section on materials and

manufacturing. They provide a review of Pt-based

catalysts including a volcano plot of the Pt3M alloys (4)

discussed in Chapter 14 by Elter. The core–shell work

is also reviewed. There are interesting discussions on

non-pgm catalysts and Pt-free noble metal catalysts.

The main conclusions are that non-pgms cannot

compete with Pt and that Pd-Co and Pd-V alloys were

of similar activity to Pt.

This chapter also opens the topic of electrocatalyst

degradation. Catalyst ripening (or particle-size



growth) is mentioned but the topic of catalyst support

corrosion is given more attention. Intriguingly, this

chapter also covers the area of catalysts for hydrogen

production but in a relatively superfi cial way. Ni, Pt,

Pd, Rh and Ru are listed as being suitable catalysts for

steam reforming, partial oxidation and autothermal

reforming of hydrocarbons.

Catalyst DegradationChapter 20, ‘Degradation Caused by Dynamic

Operation and Starvation Conditions’, by Jan Hendrik

Ohs, Ulrich S. Sauter and Sebastian Maass (Robert

Bosch GmbH, Germany) provides insights into Pt

catalyst degradation in PEMFC electrodes. There is

an interesting comparison of the Pourbaix diagrams

of carbon and Pt. The oxidation of Pt is clearly visible

for potentials above 0.8 V but clearly the corrosion of

C is problematic over a much wider operating range

of potential. The possibility of Pt leaving the electrode

structure as Pt2+ ions that are then precipitated in an

isolated and inactive band within the membrane is

described as ‘catalyst islanding’.

Chapter 30, ‘Modeling of Polymer Electrolyte

Membrane Fuel-Cell Components’, by Yun Wang

(University of California, Irvine, USA) and Ken S.

Chen (Sandia National Laboratories, Livermore, USA),

examines the use of high-fi delity modelling of the

catalyst layer to optimise the composition in terms of

pore structure and proportions of Pt, C and ionomer.

Chapter 35, ‘Design Criteria and Components for

Fuel Cell Powertrains’, by Lutz Eckstein and Bruno

Gnörich (RWTH Aachen University, Germany)

provides a very detailed overview of the design

options for fuel cell power trains. Several interesting

statistics are cited. Firstly, that for 500,000 units per

year production, fuel cell systems could be produced

for 67 €/kW of which 42 €/kW is associated with the

fuel cell stack and 17% of the total system cost is for

Pt. This is further put into perspective by comparing

a conventional internal combustion engine (ICE)

90 kW drivetrain cost of €800 versus €13,594 for the

PEMFC equivalent.

Fuel Cell MarketsThe penultimate section on System Verifi cation and

Market Introduction, Chapters 37 and 38 ‘Off-Grid

Power Supply and Premium Power Generation’ by

Kerry-Ann Adamson (Pike Research – Cleantech

Market Intelligence, UK) and ‘Demonstration Projects

and Market Introduction’ by Kristin Deason (NOW

–1.5 –1 –0.5 0 0.5 1 1.5 2

∆EOH, eV

E O, e

V

–0.5

–1.0

–1.5

–2.0

–2.5

–3.0

–3.5

–4.0

–4.5

–5.0

3

2

1

0

–1

–2

Activity

Mo

W

Fe

CoRu

Ni Rh

CuIr

Pd

PtAg

Au

Fig. 1. Trends in oxygen reduction activity plotted as a function of both the O and OH binding energy (1)



GmbH, Germany), provides encouraging reviews of

successful demonstrations and promising markets.

The fi nal section on Knowledge Distribution and

Public Awareness is a useful supplement to the purely

technical content. It includes a survey of current

national and international organisations promoting

hydrogen and fuel cells along with a short commentary

on the need to increase efforts to educate the public

about hydrogen as a fuel.

SummaryThe book, “Fuel Cell Science and Engineering:

Materials, Processes, Systems and Technology”, is a very

informative reference regarding the current progress

in a very wide range of topics in fuel cell research and

development. There is some duplication within the

various chapters and many chapters begin with the

standard description of what a fuel cell is and how it

is a clean electrochemical energy conversion device.

As can be seen from the above review, only nine of the

forty-one chapters speak directly to the issue of pgm

usage in fuel cells and fuel cell systems. Chapter 14, in

particular, does an excellent job of reviewing the very

interesting developments in reducing Pt loading using

alloys and nano-structures. A considerable amount of

the book is devoted to SOFC development that has

little relevance to pgm except perhaps with respect to

recent hydrocarbon reforming catalysts using Rh and

other pgms although this work was not well covered.

Overall, however, the book does indicate that there

is reason to be optimistic regarding the potential for

fuel cell automobiles to compete with current battery

electric vehicles in the near future.

For researchers who already have some history

with fuel cells and want to maintain their knowledge

of the general progress of fuel cell research this

could be a useful addition to one’s personal library.

For those specifi cally interested in pgm catalysis for

fuel cells, I would recommend the book “Catalysis in

Electrochemistry: From Fundamentals to Strategies for

Fuel Cell Development” (5) .

References1 J. K. Nørskov, J. Rossmeisl, A. Logadottir, L. Lindqvist, J.

R. Kitchin, T. Bligaard and H. Jónsson, J. Phys. Chem. B, 2004, 108, (46), 17886

2 V. R. Stamenkovic, B. S. Mun, K. J. J. Mayrhofer, P. N. Ross and N. M. Markovic, J. Am. Chem. Soc., 2006, 128, (27), 8813

3 J. X. Wang, H. Inada, L. Wu, Y. Zhu, Y. Choi, P. Liu, W.-P. Zhou and R. R. Adzic, J. Am. Chem. Soc., 2009, 131, (47), 17298

4 V. R. Stamenkovic, B. S. Mun, M. Arenz, K. J. J. Mayrhofer, C. A. Lucas, G. Wang, P. N. Ross and N. M. Markovic, Nature Mater., 2007, 6, (3), 241

5 “Catalysis in Electrochemistry: From Fundamentals to Strategies for Fuel Cell Development”, eds. E. Santos and W. Schmickler, John Wiley & Sons, Inc, Hoboken, New Jersey, USA, 2011

The ReviewerBrant A. Peppley is the Director of the Queen’s-RMC Fuel Cell Research Centre and has been working in the fi eld of fuel cell research for more than 26 years. His current research activities include modelling of PEMFCs, the development of new materials and fabrication technologies for fuel cell system components and the development of catalyst-coated heat transfer components for fuel processing systems.

“Fuel Cell Science and Engineering: Materials, Processes, Systems and Technology”

http://dx.doi.org/10.1595/147106713X661449 •Platinum Metals Rev., 2013, 57, (1), 70–71•


The latest market survey of platinum group metal

(pgm) supply and demand from Johnson Matthey,

“Platinum 2012 Interim Review”, was released on

13th November 2012.

PlatinumPlatinum Market Forecast to Move from Surplus to Defi cit in 2012Severe disruption to pgm mining in South Africa

as a result of labour stoppages and the closure of

marginal operations is forecast to result in a 10%

drop in worldwide platinum supplies in 2012 to

5.84 million oz. Gross demand is predicted to

remain fi rm, at 8.07 million oz, while a decline in

recycling will help decidedly shift the market into a

defi cit of 400,000 oz.

Lower Supplies and Recycling ExpectedSupplies of platinum from South Africa are forecast

to fall by 12% to 4.25 million oz, an 11-year low. With

the exception of Zimbabwe, which is set to see a rise

in output of 6% to 360,000 oz, all other producing

regions are predicted to see fl at or lower supplies.

Recovery of platinum from open loop recycling

is forecast to decline by 11% to 1.83 million oz

as weaker average pgm prices have encouraged

collectors to hold on to exhaust catalysts from end-

of-life vehicles. Jewellery scrap recycling is also

expected to fall following a strong year in 2011.

Automotive Demand to Weaken SlightlyGross platinum demand in autocatalysts is

predicted to soften by 1% to 3.07 million oz in 2012.

Although purchasing of platinum by the European

autocatalyst sector is set to decline by 14% as a

consequence of falling vehicle production and a

reduction in the market share of diesel cars, this

will be will be mostly offset by higher demand

elsewhere. Following the Great East Japan

Earthquake disaster of 2011, vehicle output in

Japan recovered strongly during 2012, stimulating

greater platinum purchasing. Additional demand

came from the strongly-performing light-duty

diesel sector in India as well as greater platinum

use in heavy-duty diesel emissions aftertreatment

worldwide.

Industrial Demand Forecast to Fall by 13%Lower demand for platinum by the glass

manufacturing industry is expected in 2012 due

to the use of metal scrapped from old glass fi bre

production facilities and the drawing down

of inventory bought during the previous year.

Demand for platinum in electrical applications

is also expected to soften due to a contraction

of purchasing by the manufacturers of hard disk

drives. However, purchasing of platinum for non-

road emissions control applications will more than

double to 130,000 oz as pgm-forcing legislation is

now in effect for various types of agricultural and

construction machinery in many markets.

Jewellery Demand to Reach a 3-Year HighDemand for platinum in the jewellery sector is

expected to reach 2.73 million oz in 2012. Gross

demand from the trade in China is forecast to grow

by 14% to 1.92 million oz as manufacturers increase

output of platinum jewellery to stock new retail

stores. In India, consumer demand for platinum

jewellery has continued to grow, prompting an

expansion of platinum jewellery manufacturing.

Investment Demand to Remain PositivePhysical investment demand for platinum is

forecast to remain positive, at 490,000 oz in 2012.

Periods of rising price have tended to attract net

investment in the physically-backed exchange

traded fund (ETF) market.

PalladiumPalladium Market Set to Swing into Large Defi citThe balance of the palladium market in 2012 is

forecast to swing by over 2 million oz from surplus to

defi cit due to lower supplies, higher gross demand

and less recycling. Supplies will contract mainly

because of lower sales of Russian state stocks,

while recycling will be constrained by subdued

pgm prices. Gross palladium demand is predicted to

rise to 9.73 million oz, driven by a return to positive

net physical investment and higher autocatalyst

purchasing, moving the palladium market into a

defi cit of 915,000 oz.

“Platinum 2012 Interim Review”



Automotive Demand to Reach a Record LevelDemand for palladium in automotive applications

is set to rise by 7% to reach a new all-time high of

6.48 million oz. Growth in global vehicle production,

a strong performance in the principally gasoline

car markets of Japan and the USA and continuing

substitution of platinum with palladium in diesel

aftertreatment formulations are all factors behind

this rise.

Industrial Demand to SoftenIndustrial demand for palladium is forecast to fall

by 3% to 2.41 million oz in 2012. A long-term trend

towards using cheaper base metal alternatives to

palladium in all but niche and high-end electrical

components continues to drive demand lower.

This will be offset somewhat by the purchasing of

palladium for process catalysts in new chemical

manufacturing plants in China.

Return to Net Positive Investment Demand, Fall in Jewellery DemandA change in investor sentiment towards palladium

ETFs is expected to result in 385,000 oz of net new

physical investment demand, a swing of 950,000 oz

compared with 2011. Gross demand for palladium

in jewellery is predicted to dampen by 11% to

450,000 oz as the metal continues to suffer from

competition and a lack of effective marketing in

China, the biggest market.

Other Platinum Group MetalsThe rhodium market is forecast to move into a

defi cit of 43,000 oz, the fi rst since 2007, as a result

of falling supplies and lower autocatalyst recycling,

as well as stronger gross demand. The return of

Japanese auto manufacturers to full production in

2012 has resulted in additional rhodium demand

while demand is also expected to benefi t from

higher physical investment purchasing and a rise

in sales to the chemical industry.

Demand for ruthenium is forecast to fall by 20%

to 770,000 oz in 2012. Purchasing by the chemical

sector is predicted to drop following unusually

high levels of purchasing in 2011, when several

ammonia plants globally bought complete new

charges of ruthenium catalyst. Ruthenium demand

in the electrical sector is expected to soften in

line with lower use by the global hard disk drive

industry.

Iridium demand is forecast to weaken by 35% in

2012 to 218,000 oz, mainly as a result of a decline

in purchasing by the electrical sector, which has

stood at exceptionally high levels in the last two

years. The main market for iridium is in crucibles

used to manufacture sapphire crystal wafers for

light-emitting diodes (LEDs).

Special Feature“Platinum 2012 Interim Review” contains a special

feature on the control of emissions of oxides

of nitrogen (NOx). Over several decades, NOx

emissions from vehicles have been mitigated by

a range of technologies driven by progressively

tighter regulations. The special feature details

some of the ways that NOx can be controlled

from vehicles, including pgm-containing three-way

catalysts and NOx traps. As legislation around the

world is extended, tightens and covers more vehicle

types, pgm demand should benefi t from integrated

catalyst solutions that combine the functionality for

NOx reduction with that to reduce other pollutants.

Availability of “Platinum 2012 Interim Review”The book is available, free of charge, as a PDF fi le

in English, Chinese or Russian from Platinum Today

at: http://www.platinum.matthey.com/. The English

version can be ordered in hard copy, by fi lling

in a form on the website, by emailing: ptbook@

matthey.com, or by writing to: Johnson Matthey,

Precious Metals Marketing, Orchard Road, Royston,

Hertfordshire SG8 5HE, UK.

NOx traps are a promising area of future pgm demand

CO+HC+H2 NOx CO

PtRh

N2 +CO2

Ba(NO3)2

Al2O3

BaCO3



BOOKS“Alkane C–H Activation by Single–Site Metal Catalysis”

Edited by P. J. Pérez (Laboratorio de Catálisis Homogénea, Departamento de Química y Ciencia de los Materiales, Unidad Asociada al CSIC, Centro de Investigación en Química Sostenible, Universidad de Huelva, Spain), Series: Catalysis by Metal Complexes, Vol. 38, Springer Science+Business Media, Dordrecht, The Netherlands, 2012, 272 pages, ISBN: 978-90-481-3697-1, £90.00,

€106.95, US$129.00

Over the past decade, much research has been

devoted to new reagents and catalysts, including those

involving pgms, that can infl uence carbon–hydrogen

bond activation, mainly because of the prospect that

C–H activation would allow the conversion of alkanes

into more valuable functionalised organic compounds.

This book describes the development in the systems

for the catalytic transformations of alkanes under

homogeneous conditions. Chapter 1 is a summary of

the main discoveries. Chapter 2 reviews the so-called

electrophilic activation, initiated by Shulpin in the

late 1960s, and the base for the Catalytica system.

Chapter 3 examines the catalytic borylation of alkanes,

discovered by Hartwig, Chapter 4 provides an updated

vision of the alkane dehydrogenation reaction.

Chapter 5 covers the oxygenation of C–H bonds and

fi nally Chapter 6 presents the functionalisation of

alkane C–H bonds by carbene or nitrene insertion.

“Celebrating Jewellery: Exceptional Jewels of the Nineteenth and Twentieth Centuries”

By D. Bennett and D. Mascetti (Sotheby’s, UK), Antique Collectors’ Club Ltd, Old Martlesham, Woodbridge, Suffolk, UK, 2012, 324 pages, ISBN: 978-1-85149-616-7,

£75.00, US$125.00

Some of the greatest and most

iconic pieces of jewellery from the

nineteenth and twentieth centuries are included in

this book. Each jewel is shown in detail, with captions

explaining the history and background to its design.

All the great jewellery designers and manufacturers

are represented. Following the discovery of diamonds

in South Africa around the 1860s, the supply of these

gems increased exponentially, enabling jewellers to

create ornaments encrusted with these gems. Platinum,

then a new metal for use in jewellery, became the metal

of choice for setting diamonds. Its combination of

hardness and rigidity, coupled with its ‘whiteness’, was

perfectly suited to the lacelike fi ligree mounts of the

time; these followed design motifs drawn from Louis

XVI ormolu furniture mounts, with swags and garlands

delicately set with variously shaped diamonds.

“Fuel Cells: Current Technology Challenges and Future Research Needs”

By N. Hikosaka Behling (USA), Elsevier BV, Amsterdam, The Netherlands, 2013, 685 pages, ISBN: 978-0-444-56325-5, €180.00

This book provides an overview

of past and present initiatives

to improve and commercialise

fuel cell technologies. It reviews

government, corporate and

research institutions’ policies and programmes related

to fuel cell development and their effect on the

success or failure of fuel cell programmes. It offers

analysis to help potential investors assess fuel cell

commercialisation activities and future prospects. It

gives policy recommendations as to what should be

done to further successfully commercialise fuel cells.

“Principles of Asymmetric Synthesis”, 2nd Edition

By R. E. Gawley (Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, USA) and J. Aubé (Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, USA), Elsevier Ltd, Kidlington, Oxford, UK, 2012, 555 pages, ISBN: 978-0-08-044860-2, €49.95

The focus of the book is on the

principles that govern relative and

absolute confi gurations in transition state assemblies.

For example, organisation around a metal atom, A1,3

strain, van der Waals interactions, dipolar interactions,

etc., are factors affecting transition state energies, and

which in turn dictate stereoselectivity via transition

state theory. The fi rst chapter provides background,

introduces the topic of asymmetric synthesis and

Publications in Brief



outlines principles of transition state theory as applied

to stereoselective reactions. Chapter 2 begins with

a discussion of practical aspects of obtaining an

enantiopure compound, and then describes methods

for analysis of mixtures of stereoisomers. Chapter

3 discusses enolate and organolithium alkylations,

while Chapter 4 covers nucleophilic additions to C=O

and C=N bonds; these two chapters are on reactions

in which one new stereocentre is formed. Chapter 5

covers aldol and Michael additions that generate at

least two new stereocentres, while Chapter 6 covers

selected cycloadditions and rearrangements. The last

two chapters are on reductions and oxidations. The

book gives many examples of pgm catalysts.

“The Rare Earth Elements: Fundamentals and Applications”

By D. A. Atwood (Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA), John Wiley & Sons, Ltd, Chichester, West Sussex, UK, 2013, 696 pages, ISBN: 978-1-1199-5097-4, £160.00, €191.50, US$265.00

This book explains the chemistry

of the lanthanide elements which

are often used alongside pgms in

catalytic and other applications. A chapter describes

the similarity of the Group 3 elements, Sc, Y, La, the

group from which the lanthanides originate and the

Group 13 elements, particularly Al, having similar

properties. The early chapters describe the occurrence

and mineralogy of the elements, with a focus on

structural features observed in compounds described

in later chapters. The majority of the chapters are

organised by the oxidation state of the elements,

Ln(0), Ln(II), Ln(III) and Ln(IV). The chapters are

further distinguished by type of compound, inorganic

(oxides and hydroxides, aqueous speciation, halides,

alkoxides, amides and thiolates and chelates) and

organometallic. The concluding chapters describe the

applications of the lanthanides in catalysis, electronic

and magnetic materials, and medical imaging, etc.

JOURNALSEnergy Science & EngineeringEditor-in-Chief: T. Kåberger; Wiley and SCI; e-ISSN: 2050-0505

Energy Science & Engineering is a new peer-reviewed,

open access journal dedicated to fundamental and

applied research on energy and its supply and use.

The journal is published jointly

by Wiley and SCI (Society of

Chemical Industry). This journal

aims to “facilitate collaboration

and spark innovation in energy

research and development”.

The journal will give priority

to research papers that are

accessible to a broad readership

and discuss sustainable, state-of-the art approaches to

“shaping the future of energy”. Topics to be covered

include:

(a) General Energy;

(b) Fossil Fuels;

(c) Energy Storage;

(d) Nuclear Energy;

(e) Renewable Energy (includes bioenergy, biofuels;

solar energy and photovoltaics; and hydrogen,

batteries and fuel cells);

(f) Power Engineering.

Special Issue: Modeling of Exhaust-Gas After-Treatment

Catal. Today, 2012, 188, (1), 1–134

This special issue of Catalysis

Today is a selection of the papers

given at the 2nd International

Symposium on Modeling of

Exhaust-Gas After-Treatment

(MODEGAT II) held in Bad

Herrenalb/Karlsruhe, Germany,

on 19th–20th September 2011. The

aim of the symposium was to support the exchange of

state-of-the-art modelling and simulation techniques

and new approaches. The location, programme and

low fee were chosen to try to boost open discussions

and new collaborations. The number of attendees was

limited to 100; 40 of them were from academia and

60 from industry. A total of 37 papers were submitted

and were presented in oral and poster presentations

in sessions, each of them focusing on an exhaust

gas aftertreatment system: three-way catalysts, diesel

oxidation catalysts, selective catalytic reduction, NOx

storage catalysts and diesel particulate fi lters.

Special Issue: Proceedings of the 10th International Conference on Catalysis in Membrane ReactorsCatal. Today, 2012, 193, (1), 1–226

ICCMR10 took place in Saint Petersburg, Russia, on

20th–24th June 2011. It was organised by Topchiev



Institute of Petrochemical

Synthesis of the Russian Academy

of Sciences and Saint-Petersburg

State Institute of Technology

(Technical University) and

sponsored by Russian Foundation

for Basic Research, Russian

Academy of Sciences and European Membrane

Society. The conference covered the preparation

of new and improved membrane materials, new

experimental and modelling achievements and

progress reports about old and new proposed

applications of membrane reactors. This special issue

contains 31 selected papers including: ‘Electrocatalytic

Properties of the Nanostructured Electrodes and

Membranes in Hydrogen-Air Fuel Cells’, ‘Hydrogen

Production from Bio-ethanol Steam Reforming

Reaction in a Pd/PSS Membrane Reactor’, ‘Hydrogen

Production from Ethanol over Pd–Rh/CeO2 with a

Metallic Membrane Reactor’, and ‘Hydrogen Transport

through a Selection of Thin Pd-Alloy Membranes:

Membrane Stability, H2S Inhibition, and Flux Recovery

in Hydrogen and Simulated WGS Mixtures’.

Special Issue: Synthesis of NanocatalystsChemCatChem, 2012, 4, (10), 1441–

1682

The ultimate goal of research and

development on heterogeneous

catalysis is to provide a

“fundamental understanding

of the nature of active sites

toward the design of effi cient

heterogeneous catalysts that

provide highest activity, 100% selectivity and long-

term stability”. This special issue of ChemCatChem

was put together with this in mind. The editorial

‘Catalyst Synthesis by Design for the Understanding of

Catalysis’ is by Shu-Hong Yu (Department of Chemistry,

University of Science and Technology of China, Hefei,

China), Franklin (Feng) Tao (Department of Chemistry

and Biochemistry, University of Notre Dame, USA)

and Jimmy (Jingyue) Liu (Department of Physics,

Arizona State University, USA). Relevant items include

‘Study of the Durability of Faceted Pt3Ni Oxygen–

Reduction Electrocatalysts’, ‘A Multi-Yolk–Shell

Structured Nanocatalyst Containing Sub-10 nm Pd

Nanoparticles in Porous CeO2’, ‘Ordered Mesoporous

Carbon Supported Colloidal Pd Nanoparticle Based

Model Catalysts for Suzuki Coupling Reactions: Impact

of Organic Capping Agents’, and ‘A Highly Selective

Catalyst for Partial Hydrogenation of 1,3-Butadiene:

MgO-Supported Rhodium Clusters Selectively

Poisoned with CO’.

Themed Issue: Homogeneous and Heterogeneous Catalysis in Industry

Catal. Sci. Technol., 2012, 2, (10),

1997–2154

In this themed issue of Catalysis

Science & Technology, advances

in modelling, biomass utilisation

and ligand design in processes

that range from high-temperature

high-pressure high-tonnage to

small-scale ambient-pressure

liquid-phase are covered. The editorial is by Johannes

G. de Vries (DSM Innovative Synthesis BV, The

Netherlands) and S. David Jackson (Department of

Chemistry, University of Glasgow, UK). Items of interest

include: ‘Synthesis of Methanol and Dimethyl Ether

from Syngas over Pd/ZnO/Al2O3 Catalysts’, ‘Direct

Coupling of Alcohols to Form Esters and Amides

with Evolution of H2 Using In Situ Formed Ruthenium

Catalysts’, ‘Steam Reforming of Ethanol at Medium

Pressure over Ru/Al2O3: Effect of Temperature and

Catalyst Deactivation’, and ‘Syngas Production by

CO2 Reforming of Methane Using LnFeNi(Ru)O3

Perovskites as Precursors of Robust Catalysts’.

ON THE WEB

Encyclopedia of Applied Electrochemistry

The Encyclopedia of Applied Electrochemistry on

SpringerReference.com will provide in alphabetical

order an authoritative compilation of entries covering

applied aspects of electrochemistry, including basic

theoretical concepts and laboratory techniques.

Find this at: http://www.springerreference.com/docs/

navigation.do?m=Encyclopedia+of+Applied+Electrochemi

stry+(Chemistry+and+Material+Science)-book161

25 Prominent and Promising Applications Using Platinum Group Metals

Founded in 1987, the IPA (International Platinum

Group Metals Association) represents the leading

mining, production and fabrication companies

in the global pgms industry, comprising platinum,



palladium, iridium, rhodium, osmium and ruthenium.

The IPA has currently fi fteen members. Its mission is

to provide a platform to address issues of common

concern and to jointly engage with stakeholders at

the international level. On the occasion of its 25th

Anniversary the IPA have put together the Fact Sheet

“25 Prominent and Promising Applications Using

Platinum Group Metals”.

Find this at: http://www.ipa-news.com/

“25 Prominent and Promising Applications Using Platinum

Group Metals”: http://www.ipa-news.com/en/fi les/25_

applications_of_pgms.pdf



CATALYSIS – INDUSTRIAL PROCESSESHeterogeneous Catalytic Chemistry by Example of Industrial ApplicationsJ. Heveling, J. Chem. Educ., 2012, 89, (12), 1530–1536

A heterogeneous metal catalyst typically consists

of the active metal component, promoters and a

support material. The metallic state itself may form

the active ingredient. Examples of practical industrial

importance are used by the author to highlight

important principles of catalysis. These include for the

pgms: ammonia oxidation (Pt-Rh), automotive exhaust

catalysts (Pt, Pd and Rh) and oxidation catalysts (Pt-Bi).

CATALYSIS – REACTIONSPhotocatalytic Hydrogen Generation in the Presence of Ethanolamines over Pt/ZnIn2S4

under Visible Light IrradiationY. Li, K. Zhang, S. Peng, G. Lu and S. Li, J. Mol. Catal. A: Chem., 2012, 363–364, 354–361

The photocatalytic activity for H2 evolution and

decomposition of ethanolamine (EA), diethanolamine

(di-EA) and triethanolamine (tri-EA) as electron donors

(pollutants) over Pt/ZnIn2S4 were investigated. The Pt

was deposited on ZnIn2S4 by in situ photoreduction

of H2PtCl6. The order of activity for H2 evolution was:

tri-EA di-EA > EA. The order of adsorption intensity

of the ethanolamines on ZnIn2S4 was: EA > di-EA >> tri-

EA. The order of activity was found to depend on their

molecular structure and adsorption performance.

Application of an Air-and-Moisture-Stable Diphenylphosphinite Cellulose-Supported Nanopalladium Catalyst for a Heck ReactionQ. Du and Y. Li, Res. Chem. Intermed., 2012, 38, (8), 1807–1817

The title catalyst (Cell–OPPh2-Pd0) was prepared from

cellulose and chlorodiphenylphosphine in pyridine,

followed by treatment with an ethanol solution of

PdCl2. The prepared catalyst was air- and moisture-

stable. Phenyl halides were coupled with alkenes in

DMF under air, to afford the corresponding products

in good yields. The catalyst could be easily recovered

by fi ltration and reused for up to 6 cycles.

Hydrogenation of Phenol Using Silica-Supported Pd and PdAu Catalysts in the Presence of H2 and O2

S. Okada, K. Fujiwara, T. Kamegawa, K. Mori and H. Yamashita, Bull. Chem. Soc. Jpn., 2012, 85, (9), 1057–1059

2-Cyclohexen-1-one was obtained from phenol

by hydrogenation under H2 and O2 gases using a

Pd/SiO2 catalyst. The effects of the H2:O2 ratio, solvent

and alloying Pd with Au were all investigated. Similar

transformations to form corresponding cyclic enones

were achieved with other phenolic type compounds.

Iridium-Catalyzed Intramolecular [4 + 2] Cycloadditions of Alkynyl HalidesA. Tigchelaar and W. Tam, Beilstein J. Org. Chem., 2012, 8, 1765–1770

Ir-catalysed intramolecular [4 + 2] cycloadditions of

diene-tethered alkynyl halides were carried out using

[IrCl(cod)]2. The most suitable phosphine ligand for

the reaction was dppe. The cycloadditions proceeded

smoothly at 90ºC to give the halogenated cycloadducts

in good yield (75–94%). No oxidative insertion of the Ir

into the carbon–halide bond was observed.

EMISSIONS CONTROLA Three-Electrode Column for Pd-Catalytic Oxidation of TCE in Groundwater with Automatic pH-Regulation and Resistance to Reduced Sulfur Compound Foiling

Abstracts

15–20% aq. H2O2

OHR

R

5% Pt-5% Bi/C OR

R

H

RH, Cl; R = H orR = H; R = CH2-C6H4-COONa

2-Butyl-5-formylimidazole derivatives

(up to 100%)

N

N

N

N

J. Heveling, J. Chem. Educ., 2012, 89, (12), 1530–1536



S. Yuan, M. Chen, X. Mao and A. N. Alshawabkeh, Water Res., 2013, 47, (1), 269–278

A hybrid electrolysis and Pd-catalysed oxidation

process was evaluated for the degradation of

trichloroethylene (TCE) in groundwater. A three-

electrode (one anode and two cathodes) column was

used to automatically develop a low pH in the vicinity

of Pd and neutral effl uent. Simulated groundwater

containing up to 5 mM bicarbonate could be acidifi ed

to below pH 4 in the vicinity of Pd using a total of

60 mA with 20 mA passing through the third electrode.

By packing 2 g of Pd/Al2O3 pellets in the developed

acidic region, the column effi ciency for TCE oxidation

in simulated groundwater (5.3 mg l–1 TCE) increased

from 44% to 59% and 68% with increasing Fe(II)

concentration from 0 mg l–1 to 5 mg l–1 and 10 mg l–1,

respectively. This process may be used to control the

fouling caused by reduced sulfur compounds (RSCs)

because the in situ generated reactive oxidising

species such as O2, H2O2 and ·OH can oxidise RSCs.

A New Oxygen Storage Capacity Material of a Tin-Doped Ceria–Zirconia-Supported Palladium–Alumina Catalyst with High CO Oxidation ActivityQ. Dong, S. Yin, C. Guo and T. Sato, Chem. Lett., 2012, 41, (10), 1250–1252

Ce0.5Zr0.4Sn0.1O2/Pd–Al2O3 composite catalysts were

prepared by mechanical mixing of Ce0.5Zr0.4Sn0.1O2

and 2 wt% Pd--Al2O3 powder (weight ratio of

Ce0.5Zr0.4Sn0.1O2:Pd–Al2O3 = 50:50). These composites

had a high BET surface area of 38 m2 g–1 and exhibited

a high oxygen storage capacity and high CO oxidation

activity at low temperatures, even after calcination at

1000ºC for 20 h. The authors state that the prepared

Ce0.5Zr0.4Sn0.1O2/Pd–Al2O3 has potential as a key

material in advanced catalytic converters for the

design of three-way catalysts.

Application of a Re–Pd Bimetallic Catalyst for Treatment of Perchlorate in Waste Ion-Exchange Regenerant BrineJ. Liu, J. K. Choe, Z. Sasnow, C. J. Werth and T. J. Strathmann, Water Res., 2013, 47, (1), 91–101

Re–Pd/C was shown to reduce ClO4– to Cl– in waste

ion-exchange (IX) brines. The catalyst activity was not

inhibited in synthetic NaCl-only brine compared to DI

water. Re–Pd/C was deactivated by reaction with excess

NO3– present in the real waste IX brine. The deactivation

of the Re–Pd/C catalyst could be prevented by

pretreating NO3– with an In–Pd/Al2O3 catalyst.

FUEL CELLS

Self-Recovery of Pd Nanoparticles That Were Dispersed over La(Sr)Fe(Mn)O3 for Intelligent Oxide Anodes of Solid-Oxide Fuel CellsT. H. Shin, Y. Okamoto, S. Ida and T. Ishihara, Chem. Eur. J., 2012, 18, (37), 11695–11702

High-performance ‘intelligent oxide anodes’ for SOFCs

have been prepared. These anodes can achieve self-

recovery from power density degradation during the

redox cycle by using a Pd-substituted La(Sr)Fe(Mn)O3

cell as an oxide anode. The recovery of the power

density could be explained by the formation of Pd

NPs, which were self-recovered through reoxidation

and reduction. This process was shown to be effective

for improving the durability of SOFC systems when

under severe operating conditions.

A Dual-Chambered Microbial Fuel Cell with Ti/Nano-TiO2/Pd Nano-Structure CathodeM. G. Hosseini and I. Ahadzadeh, J. Power Sources, 2012, 220, 292–297

The title cathode was used in a dual-chambered

microbial fuel cell with a graphite anode and a

Flemion cation exchange membrane. Ti/nano-TiO2/Pd

gave satisfactory long term performance as a cathode

to reduce water dissolved oxygen. The maximum output

power of the cell was about 200 mW m–2 normalised to

the cathode surface area. The open circuit potential

of the cell was about 480 mV and the value of the

short circuit current was 0.21 mA cm–2 of the cathode

geometric surface area.

Additive-Free Fabrication of Spherical Hollow Palladium/Copper Alloyed Nanostructures for Fuel Cell ApplicationC. Hu, Y. Guo, J. Wang, L. Yang, Z. Yang, Z. Bai, J. Zhang, K. Wang and K. Jiang, ACS Appl. Mater. Interfaces, 2012, 4, (9), 4461–4464

Spherical hollow Pd-Cu alloyed nanostructures

supported on MWCNTs were obtained by alloying

through a one-pot preparative method. A Pd(II) salt

and a Cu(II) salt (atomic ratio 1:1) and MWCNTs were

simultaneously dispersed into ethylene glycol in a

stainless steel autoclave, and the pH was adjusted to

12. Then it was sealed and heated at 160ºC for 6 h. The

PdCu/MWCNTs exhibited a higher electrochemical

active surface area than that of Pd/MWCNTs and

therefore their electrocatalytic activity for formic acid

oxidation was enhanced.



METALLURGY AND MATERIALSThermal Stability of Grain Structure and Material Properties in an Annealing-Twinned Ag–8Au–3Pd Alloy WireT.-H. Chuang, H.-C. Wang, C.-H. Tsai, C.-C. Chang, C.-H. Chuang, J.-D. Lee and H.-H. Tsai, Scr. Mater., 2012, 67, (6), 605–608

A large number of annealing twins can be observed in a

Ag–8Au–3Pd wire. In contrast to the rapid grain growth

in Au and Cu wires during ageing at 600ºC, the grain

size of this alloy wire remained almost unchanged.

The annealing twins in this alloy wire exhibited

increasing strength and elongation with ageing time.

The electrical resistivity remained constant.

CHEMISTRYHigh Energy Resolution Off-Resonant Spectroscopy at Sub-Second Time Resolution: (Pt(acac)2) DecompositionJ. Szlachetko, M. Nachtegaal, J. Sá, J.-C. Dousse, J. Hoszowska, E. Kleymenov, M. Janousch, O. V. Safonova, C. König and J. A. van Bokhoven, Chem. Commun., 2012, 48, (88), 10898–10900

The decomposition of Pt(acac)2 in H2 induced by

fl ash heating was investigated. The changes in the local

Pt structure were followed using in situ high energy

resolution off-resonant spectroscopy (HEROS). The

metal complex was fl ash heated to 150ºC and HEROS

spectra were collected every 500 ms. The Pt(acac)2

decomposition was shown to consist of a two-step

reduction process of the Pt(II) species.

ELECTRICAL AND ELECTRONICSInfl uence of Thin Platinum Layer on the Magnetic Properties of Multiple Layers of CVD Cobalt Thin FilmsN. Deo, M. F. Bain, J. H. Montgomery and H. S. Gamble, J. Mater. Sci.: Mater. Electron., 2012, 23, (10), 1881–1886

Co layers were deposited by MOCVD on oxidised Si

substrates at 450ºC, in H2 at ambient temperature

with 2 Torr processing pressure. Pt layers were then

deposited by E-beam evaporation in another vacuum

system. Multiple layers of Co/Pt/Co and Co/Pt with

Co thickness 15 nm and 30 nm and a 1.5 nm Pt

spacer layer showed signifi cant change in magnetic

properties (coercivity Hc and magnetisation Ms). They

had soft magnetic properties with Hc values of 51 Oe

and 49 Oe, respectively, which are signifi cantly less

than the Hc values of single Co layers on oxidised Si.

NANOTECHNOLOGYControlled Synthesis of Concave Tetrahedral Palladium Nanocrystals by Reducing Pd(acac)2 with Carbon MonoxideH. Zhu, Q. Chi, Y. Zhao, C. Li, H. Tang, J. Li, T. Huang and H. Liu, Mater. Res. Bull., 2012, 47, (11), 3637–3643

Concave tetrahedral Pd nanocrystals with uniform

sizes were prepared using Pd(acac)2 as a precursor,

PVP as a stabiliser and CO as a reducing agent

under atmospheric pressure. The best CO fl ow rate,

temperature and time for the formation of the ideal

concave tetrahedral Pd nanocrystals were 0.033 mL s−1,

100ºC and 3 h, respectively. In the absence of CO, the

reaction did not occur.

Microfl uidic Size Selective Growth of Palladium Nano-Particles on Carbon Nano-OnionsF. Md Yasin, R. A. Boulos, B. Y. Hong, A. Cornejo, K. S. Iyer, L. Gao, H. T. Chua and C. L. Raston, Chem. Commun., 2012, 48, (81), 10102–10104

Size selective growth of Pd NPs (2–7 nm in diameter)

on the surface of C nano-onions (CNOs) in water

involved pretreating the CNOs with p-phosphonic acid

calix[8]arene, 1, then mixing with H2PdCl4 followed by

dynamic thin fi lm processing under H2 in a vortex fl uidic

device (VFD). The control in particle size by varying the

speed using the VFD was consistent with variations in

mass transfer of H into the dynamic thin fi lms.

OH

OH

OH

OH

HO

HO

HO

HO

PO3H2

PO3H2

PO3H2

PO3H2H2O3P

H2O3P

H2O3P

H2O3P

F. Md Yasin et al., Chem. Commun., 2012, 48, (81), 10102–10104

1



CATALYSIS – APPLIED AND PHYSICAL ASPECTSPolymetallic Reforming CatalystChina Petroleum & Chemical Corp, Chinese Appl. 102,441,377; 2012

The catalyst consists of (in wt%): 0.1–2 Pt; 0.01–2

Ir; 0.1–1 Sn; and 0.5–5 Cl on an Al2O3 support. An

impregnating solution with Ir acetylacetonate, Pt(II)

acetylacetonate, C6–C10 alkane and C6–C7 aromatic

hydrocarbon is fi rst prepared. The Sn containing

Al2O3 support is impregnated with the impregnating

solution at 0–50ºC for 10–200 h; the weight ratio of water

to chlorine is controlled at 1--150:1; water-chlorine

activation of impregnated solid is carried out at

370–700ºC; and the product is reduced to obtain the

polymetallic reforming catalyst.

EMISSIONS CONTROLSupported Bilayer Three-Way CatalystMitsubishi Motors Corp, Japanese Appl. 2012-154,250

The exhaust gas treatment for an internal combustion

engine consists of an exhaust gas treatment unit in

the exhaust pipe and an air-fuel ratio controller. The

treatment unit has a supported bilayer TWC comprising

a Rh-containing upper layer and a Pd-containing lower

layer. The alkali metal content in the lower layer is

higher than in the upper layer. The controller controls

the air-fuel ratio within a predetermined range based

on a theoretical ratio.

FUEL CELLSFuel Cell Catalyst PreparationBlue Nano Inc, World Appl. 2012/102,714

A fuel cell catalyst consist of a 3D nanoporous Au

with additional coatings of Pt, Pd, Ru and/or Bi. The

catalyst has a thickness of 0.05–50 μm; a width of

0.1–100 cm; and a length of 0.2–1000 cm. This catalyst

is prepared by immersing Au-Ag alloy in concentrated

HNO3 from 1–1000 minutes at 0–60ºC, to selectively

remove Ag to form a nanoporous Au, this is then

rinsed in deionised water and one (or more layers)

of Pt is deposited onto the surface. Either Bi or Ru are

deposited onto the surface of the nanoporous Au-Pt

resulting in a nanoporous Au-Pt-Bi or nanoporous

Au-Pt-Ru catalyst.

Core–Shell Catalytic NanoparticlesUTC Power Corp, World Appl. 2012/105,978

A process for forming core–shell catalytic NPs

comprising a Pd core enclosed by a Pt shell is claimed.

The percentage of the surface area of the core–shell

catalytic NPs is increased by storing in a hydrogen

environment for absorbing hydrogen into the Pd core

and depositing Pt atoms on the surface of the core–

shell catalytic NPs by reducing a Pt salt, selected from

K2PtCl4, H2PtCl4, Pt(CN)2, PtCl2, PtBr2 and Pt(acac)2, with

hydrogen absorbed into the Pd core. The percentage

of surface area of the core–shell catalytic NPs covered

by Pt can also be increased by subjecting these NPs

to ~50 potential cycles between 0.65 V and 1.0 V with

~5 seconds at each potential, before incorporating into

the catalyst layer of an electrochemical cell. The mass

activity of the core–shell catalytic NPs is increased by

~20% after the potential cycling.

Electrode CatalystSamsung Electronics Co Ltd, US Appl. 2012/0,196,207

A fuel cell electrode catalyst consists of Pd, a transition

metal selected from: Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn;

and a precious metal which has a higher standard

reduction potential than the transition metal. The

precious metal is selected from: Pt, Rh, Ir, Au and Ag. The

catalyst has a C-based support. The electrode catalyst

is formed by substituting transition metal atoms in the

surface of a fi rst catalyst with precious metal atoms by

mixing the fi rst catalyst, the precious metal precursor

and a glycol-based solvent or an alcohol-based solvent

and heat treating the mixture at ~80–400ºC for ~1–4 h.

METALLURGY AND MATERIALSPlatinum Base Alloy in JewelleryKrastsvetmet, Russian Patent 2,439,181; 2012

The Pt base alloy consists of (in wt%): 95.0–95.5 Pt;

1.5–3.5 Co; 0.5–less than 1.0 Ga; and the remainder

is Cu. This alloy has good casting ability, is not prone

to pore formation, has satisfactory microhardness of

1900 MPa and is suitable for jewellery manufacture by

investment microcasting.

APPARATUS AND TECHNIQUEPlatinum Alloy Spark PlugJ. T. Boehler and E. P. Passman, US Appl. 2012/0,220,180

Patents



The process for manufacturing a spark plug consists

of securing a Pt-based alloy electrode tip to both

the centre and side ground electrodes by resistance

welding. The Pt-based alloy comprises of (in wt%): 20–

35 Pd; 0–15 Ir; and the remainder is Pt, e.g. the Pt alloy

comprises: 35 wt% Pd; 10 wt% Ir; and 55 wt% Pt. The

electrode tips are confi gured as a pad, rivet or a wire.

Catalyst for Life Support SystemT. A. Nalette and C. Eldridge, US Appl. 2012/0,258,013

A catalyst for a life support system consists of Pt

disposed on TiO2 support particles. The surface area is

variable and the % Pt is a percentage of the combined

weight of Pt and the TiO2 support particles. The ratio of

the surface area:% Pt is between 5 and 50 m2/% Pt g.

The surface area of the catalyst is ~150 m2 g–1 and Pt

is 3–30 wt%. The ratio of % Pt:pore volume is between

7.5 and 100% Pt g cm–3. The catalyst is disposed within

the air conditioning passage in a life support system.

MEDICAL AND DENTALFlexible Circuit Electrode Array for Artifi cial VisionJ. M. Neysmith et al., US Appl. 2012/0,192,416

The method of manufacturing a fl exible circuit

electrode array involves the following steps: a polymer

base layer is deposited, a fi rst metal layer is deposited

onto this base layer and patterned to form the fi rst

metal traces, a polymer interlayer is deposited on

the base layer and is patterned to provide vias, and

a second metal layer is deposited on the interlayer

and is patterned to form the second metal traces. A

polymer top layer is deposited on the interlayer and

the second metal traces to form a fl exible circuit.

Electrodes are electroplated through openings in the

polymer top layer which protrude above this layer. This

is embedded in a curved body which conforms to

the spherical curvature of the retina and is useful for

retinal stimulation to create artifi cial vision. The metal

is selected from Pt, Pd, Rh, Ir, Ir oxide, Ru, Ru oxide,

Ti, Au, Ag, Nb and TiN. The polymer is selected from

polyimide, thermoplastic polyimide, silicone, parylene,

LCP, epoxy resin, PEEK, TPE or a mixture. During the

stage of depositing a metal, a Ti adhesion layer and Pt

conducting layer are preferably deposited.

Gold-Palladium Alloy in Medical DevicesKunming Institute of Precious Metals, Chinese Appl. 102,517,470; 2012

The Au-Pd alloy consists of (in wt%): 5–30 Pd; 0.1–5 Nb;

0.1–5 Zr; 0.1–5 Mo; 0.1–5 Ta; 0.1–5 Yb; 0.1–5 Gd; 0.1–5

Tb; and the remainder is Au. The preparation method

involves batching, smelting, casting, rolling, drawing

and heat treating. The advantages of the Au-Pd alloy

are high hardness, high wear resistance, high corrosion

resistance, no toxicity, no irritation to humans and high

biocompatibility. This alloy could be widely used as

dental and acupuncture materials.

PHOTOCONVERSIONTridentate Bis-Carbene ComplexesUniversal Display Corp, World Appl. 2012/116,234

A process for making tridentate bis-carbene

complexes of Ru and Os is claimed. The use of DMSO

solvates of Ru(II) and Os(II) halide salts gives a good

yield of the corresponding complexes. The method of

manufacturing involves mixing a salt, MX2Ln, where M

is Ru or Os, X is Cl, L is DMSO and n is 4, with carbene

precursors, a carbene forming agent selected from

Ag2O or Cu(I) alkoxide and a polar solvent selected

from 2-methoxyethanol, 2-ethoxyethanol or a mixture,

and heating the reaction mixture. These complexes

may be used in OLEDs for improved performance.

Preparing Luminescent Iridium ComplexesBeijing Normal Univ., Chinese Appl. 102,399,181; 2012

The preparation of Ir complex, 1, involves adding

IrCl3•3H2O, the corresponding 6-aryl-2,2-bipyridine

ligand and a solvent selected from ethylene glycol

ethyl ether, butyl ether, butanol, toluene, DMSO and

DMF, into a three-neck fl ask, reacting under refl ux at

100–160ºC, and stirring for 1--3 days. In 1 m = 0–3; l = 0–4;

R1, R1, R2, R2, R3 and R3 are selected from deuterium,

tritium, halogen, cyano, amino, nitro, hydroxy, carboxy,

or substituted or unsubstituted ether group/ester

Chinese Appl. 102,399,181; 2012

1

(R2)n

(R3)k

(R1)l

(R2)n

(R3)k

(R1)m

N N

Ir

N

N



group/C1–C50 alkyl/C2–C50 alkenyl/C2–C50 alkynyl/

C3–C50 cycloalkyl/C1–C50 alkoxy/C5–C50 alkenyl

aryl/C3–C50 heteroaryl; n = 0–3; and k = 0–4.

REFINING AND RECOVERYSeparation of RhodiumSumitomo Metal Mining Co Ltd, Japanese Appl. 2012-158,778

The process of separating Cu and Rh from raw

materials involves forming a Cl leaching solution with

gaseous Cl2 followed by an extraction process which

involves solvent extracting Cu from the leaching

solution. Steps (a)–(c) are carried out between the

leaching and extraction process and the resulting

Cu-removed mother liquor is fed to the extraction

process: (a) the leaching solution is neutralised by

adding alkali to control the pH to 7–9, resulting in a

hydroxide precipitate; (b) this is then redissolved by

adding H2SO4, producing a solution of hydroxide;

and (c) the hydroxide solution is crystallised by

heating and concentrating then cooling to separate

the precipitated Cu sulfate crystal and Cu-removed

mother liquor. This method decreases the loss of Rh

in Cu sulfate.

Extraction from Spent Platinum Alloy GauzeS. Yao et al., Chinese Appl. 102,586,607; 2012

The process for extracting Pt, Rh and Pd from spent Pt

alloy gauze involves dissolving the gauze in HCl and

HNO3, removing the nitro group, treating with NaCl,

fi ltering to obtain the complexing solution of Pt, Rh

and Pd, separating Pt through NH4Cl precipitation,

separating Rh and Pd with NaNO2 complexing method,

purifying Rh with ammonium hexanitrosorhodate

method, purifying Pd with dichlorodiammine

palladium(II) method, adding N2H4•H2O, reducing

to acquire spongy Pt, Pd and Rh powders, vacuum

drying, roasting and repurifying. The extracted Pt, Pd

and Rh have a purity of >99.9%.

Recovery of Platinum from Electronic ScrapSiberian Federal Univ., Russian Patent 2,458,998; 2012

A process for recovering Pt from electronic scrap

involves crushing of the scrap and melting in a

furnace using a molten collector, comprising metallic

Bi with 0.5–1.0% In. This is mixed with the electronic

scrap at a ratio of 2.0–2.5:1 by weight at 800ºC and

kept at this temperature for 30–45 minutes, followed

by an increase in the furnace temperature to 900–

1000ºC. The obtained Bi-Pt alloy melt is oxidised by

air blowing with the transition of Bi into its oxide and

conversion of Pt into a Pt-rich globule. The advantages

of this method are that it is low cost and is relatively

simple.



Catalysis “After the Goldrush”

Cardiff University, UK, has recently been awarded

European Union (EU) funding for a new programme

entitled “After the Goldrush” (1). This programme aims

to explore the implications of discoveries made over

the last 25 years of intensive research into catalysis by

gold and so accelerate the discovery and development

of other catalytic materials such as those based on

platinum group metals (pgms), which may hold the

key to solving many of the pressing challenges facing

us now and in the future.

Gold and the Platinum Group MetalsThe independent discoveries that gold can catalyse the

hydrochlorination of acetylene (2) and that it shows

good activity in the oxidation of carbon monoxide (3)

marked the beginning of the current era of interest in

nanoparticle gold catalysis. What followed over the

next few decades can be seen as a global and highly

productive screening exercise, which has generated

a long list of potential applications. A mong the most

promising end-uses for gold are carbon monoxide

clean-up either by preferential oxidation (4) or by

water gas shift (5), selective hydrogenation (6) and

dehydrogenation (7) of hydrocarbons and oxygenates,

and oxygen insertion through formation of a peroxide

intermediate (8). For several of these reactions, gold

has impressive catalytic activity (2–5).

Just one gold-containing catalyst has so far made it

into the marketplace, and it is notable that palladium

is a key constituent: supported gold-palladium has

become established as the catalyst of choice in the

now dominant fl uidised-bed process for producing

vinyl acetate monomer (9). This apparently slow

uptake by industry needs to be seen in the context

of the 10–15 year development time required for

many catalytic processes, which may well mean

that there are more gold or gold-pgm catalysts in the

pipeline. However, it is also clear that there are specifi c

obstacles on the route to commercialising any new

catalytic technology that relies on gold. Some of these,

such as the high cost of the metal per troy ounce, are

beyond the control of the research community, but

others, such as poor durability of the catalysts or the

irreproducibility of the preparative methods, can only

be solved in the laboratory.

Fundamental UnderstandingIt is too soon to put a value on the commercial

impact of gold catalysts, but the progress made in

understanding catalysis on the nanoscale cannot

be understated and will have broad implications

for other metals including pgms. The study of gold

catalysis has revealed to us the key interdependence

between the size of a metal particle, its morphology

and the extent of its interaction with the support

material (10). It has made us push existing

characterisation techniques to new limits (11),

develop new methods for probing the active site

(12), and ask fundamental questions about why the

surface reactivity of near-neighbours in the Periodic

Table can vary so much (13). It may even be leading

us towards more active, selective and durable

catalyst formulations in which gold might be an

essential but subsidiary component alongside other

metals (14). A representative study of gold and gold-

palladium nanoparticles is shown in Figure 1 (15).

With hindsight we can now appreciate how the

publication of the seminal papers on gold catalysis

(2, 3) coincided with tetrachloroauric acid becoming

commercially available, making the preparation of

supported gold catalysts much simpler and, in turn,

opening the fl oodgates onto a largely untouched area

of scientifi c study. Although it is often asked whether

the study of other catalytic materials has suffered as

a consequence, the publication rates for the pgms

suggest otherwise (Figure 2). Rather than dwell on

this question, however, it is probably more productive

to consider how much of the emergent learning from

the work on gold is either generic or transferable to

other areas of catalysis. It is exactly this approach

that the Cardiff Catalysis Institute will be taking in its

programme “After the Goldrush”.

Over a relatively short time span, gold catalysis has

become a dynamic and highly creative fi eld. The

FINAL ANALYSIS



Fig. 1. Scanning transmission electron microscopy-high-angle annular dark-fi eld imaging (STEM-HAADF) images of metallic nanoparticles: (a) and (c): pure gold; (b) and (d): bimetallic gold-palladium nanoparticles with high selective oxidation activity. (Regions within the nanoparticle with a higher local concentration of gold appear brighter than the palladium-rich areas by virtue of the higher atomic number of gold.) (Reproduced by permission of The Royal Society of Chemistry (15))

2 nm 2 nm 2 nm 2 nmAu AuAu-Pd Au-Pd

(a) (b) (c) (d)

4000 3000 2000

1000

0N

umbe

r of

sci

entifi

c p

ublic

atio

ns

Year

(a)

Gold

Palladium

PGMs (pro rated)

Num

ber

of p

aten

ts

2006 2007 2008 2009 2010 2011Year

3000

1500

2000

1500

1000

500

0

(b)

2006 2007 2008 2009 2010 2011

Gold

Palladium

PGMs (pro rated)

Fig. 2. Publications featuring gold, palladium or pgms with the role ‘catalyst use’ in: (a) scientifi c literature, taken from the Chemical Abstracts database; (b) patent literature, for which the numbers refer to the year of publication of the basic patent excluding subsequent family members. The numbers for pgms are pro rated (i.e. calculated from the exact breakdown for palladium)



programme “After the Goldrush” will take the learning

so far gained and use it to build on the already

substantial knowledge base that exists in the parallel

fi eld of precious metal catalysis. It is a simple rationale.

By adding new impetus to the study of the classic

catalytic metals such as platinum, palladium, rhodium

and ruthenium, we will greatly increase our chances

of developing breakthrough technologies, which we

need in order to address the pressing global challenges

that we face. These include upgrading waste, the

sustainable synthesis of chemical intermediates and

products, and the decarbonisation of transport.

STAN GOLUNSKI

Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK


AcknowledgementThe author would like to thank Richard Seymour

of Technology Forecasting and Information at

the Johnson Matthey Technology Centre, Sonning

Common, UK.

References 1 AFTERTHEGOLDRUSH, Addressing global sustainability

challenges by changing perceptions in catalyst design: http://cordis.europa.eu/projects/rcn/102021_en.html (Accessed on 19th November 2012)

2 G. J. Hutchings, J. Catal., 1985, 96, (1), 292

3 M. Haruta, T. Kobayashi, H. Sano and N. Yamada, Chem. Lett., 1987, 16, (2), 405

4 J. Zhang, Y. Wang, B. Chen, C. Li, D. Wu and X. Wang, Energy Convers. Manage., 2003, 44, (11), 1805

5 D. Tibiletti, A. Amieiro-Fonseca, R. Burch, Y. Chen, J. M. Fisher, A. Goguet, C. Hardacre, P. Hu and D. Thompsett, J. Phys. Chem. B, 2005, 109, (47), 22553

6 H. Yoshitake and N. Saito, Microporous Mesoporous Mater., 2013, 168, 51

7 M. Ojeda and E. Iglesia, Angew. Chem. Int. Ed., 2009, 48, (26), 4800

8 A. K. Sinha, S. Seelan, S. Tsubota and M. Haruta, Top. Catal., 2004, 29, (3–4), 95

9 D. T. Thompson, Platinum Metals Rev., 2004, 48, (4), 169 and references therein

10 D. A. H. Cunningham, W. Vogel, H. Kageyama, S. Tsubota and M. Haruta, J. Catal., 1998, 177, (1), 1

11 G. J. Hutchings and J. K. Edwards, ‘Application of Gold Nanoparticles in Catalysis’, in “Metal Nanoparticles and Nanoalloys”, eds. R. L. Johnstone and J. P. Wilcoxon, Frontiers of Nanoscience, Elsevier Ltd, Oxford, UK, 2012, Vol. 3, pp. 249–293

12 A. Janz, A. Köckritz, L. Yao and A. Martin, Langmuir, 2010, 26, (9), 6783

13 G. C. Bond, Platinum Metals Rev., 2000, 44, (4), 146

14 M. Sankar, N. Dimitratos, P. J. Miedziak, P. P. Wells, C. J. Kiely and G. J. Hutchings, Chem. Soc. Rev., in press

15 R. C. Tiruvalam, J. C. Pritchard, N. Dimitratos, J. A. Lopez-Sanchez, J. K. Edwards, A. F. Carley, G. J. Hutchings and C. J. Kiely, Faraday Discuss., 2011, 152, 63

The AuthorStan Golunski is Professor of Catalysis at the Cardiff School of Chemistry and Deputy Director of the Cardiff Catalysis Institute, Cardiff University, UK. His research activities include the fundamentals of catalyst design as well as the application of heterogeneous catalysis in emissions control, fuel reforming and chemical manufacturing processes. He is one of the co-investigators on the programme “After the Goldrush”, which is directed by Professor G. J. Hutchings FRS.

EDITORIAL TEAM

Jonathan ButlerPublications Manager

Sara ColesAssistant Editor

Ming ChungEditorial Assistant

Keith WhitePrincipal Information Scientist


Platinum Metals Review is Johnson Matthey’s quarterly journal of research on the science and technologyof the platinum group metals and developments in their application in industry

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