PLATINUM METALS REVIEW - · PDF filePLATINUM METALS REVIEW A Quarterly Survey of Research on...

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PLATINUM METALS REVIEW A Quarterly Survey of Research on the Platinum Metals and

of Developments in their Application in Industry www.matthey.com and www.platinurn,matthey.com

VOL. 46 OCTOBER 2002 NO. 4

Contents

Catalysis for Low Temperature Fuel Cells Ey M. P Hogarth and I R. Ralph

The Chemistry of the Platinum Group Metals By John Evans

Platinum Metals in Biological and Medicinal Chemistry By Matthew D. Hall

An Equilibrium in Catalyst Optimisation and Development? ByG. R. Owen

Structural Changes and Their Kinetics in Hydrogen-Containing Palladium Systems

By V: M. Avdjukhina, A. A. Katsnelson and G. t? Revkevich

Polymer-Supported Rhodmm Catalysts Soluble in sc-COz

9th International Platinum Symposium By R. G. Cawthorn

Recyclable Ruthenium-BINAP Catalysts

A C F Power Coatingsm By Paul Williams

Electrically Induced Phosphorescence

Abstracts

New Patents

Indexes to Volume 46

146

165

166

167

169

176

177

180

181

187

188

192

195

Communications should be addressed to: The Editor, Susan V. Ashton, Platinum Metals Review, [email protected] Johnson Matthey Public Limited Company, Hatton Garden, London EC1N 8EE

Catalysis for Low Temperature Fuel Cells PART 1 1 1 : CHALLENGES FOR THE DIRECT METHANOL FUEL CELL

By M. P. Hogarth and T. R. Ralph Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.

The direct methanol fuel cell (DMFC) is a low temperature fitel cell operating ut temperutures of30 to 130°C. The DMFC i s powered by CI liquidfie1 (usually considered essentia1,for transport uses) and is therefore regarded by some as the idea1,fuel cell system. I I I this piper, the DMFC is cornpared to the hydrogen-fuelled proton exchange mentbrane firel cell (PEMFC) which was discussed in detail in the Jaiiuaty and July issues. While a typical DMFC is less eficient than a PEMFC, work to improve its performance with new electrocatulyst murerials j o r utilisation in the membrane electrode assemblies has proved successfiil. This work is described here and some possible commercial uses j o r the DMFC are also considered.

Two of the most advanced low temperature fuel cells are the proton exchange membrane fuel cell (PEMFC) and the direct methanol fuel cell (DMFC). The DMFC directly consumes liquid fuel (methanol), while the PEMFC is fuelled by hydrogen. Operating a fuel cell with liquid fuel is considered by some to be essential for transport applications - for compatibility with the existing petroleum distribution network. The DMFC also has some system-related advantages over the PEMFC, making it of interest to fuel cell developers. For instance, the DMFC has no need for a fuel processor (or reformer) to convert a liquid hydrocarbon fuel (gasoline) into a consumable source of hydrogen. This considerably reduces the complexity and cost of the system. The DMFC system does not require the complex humidification and heat management hardware modules used in the PEMFC system: the d u t e methanol-water mixtures circulating around the DMFC provide the necessary humidification and heat management.

If it can meet the performance required of a commercially viable device, the DMFC system will be potentially more cost effective than the PEMFC. Performance has been a major problem for the DMFC: it typically produces only one third of the PEMFC's power density. Hence, the DMFC community has made great efforts to bring the performance closer to that of the PEMFC, and particularly to extend the maximum operating temperature. The majority of the work has involved

developing materials, such as new anode and cathode electrocatalysts and new proton conducting polymers, to promote the efficiency of the membrane electrode assemblies (MEiAs) used in the DMFC stack. Advanced MEA designs have also been developed. Since most effort has been directed towards increasing the efficiency of the MEA components, the DMFC system itself has remained relatively undeveloped compared to the PEMFC - particularly for transport use.

However, interest in producing low temperature (< 60°C) ambient-pressure portable DMFC systems has increased recently. This is because the power densities now accessible by state-of-the-art MEAs may be enough for these systems to become competitive with leading secondary battery technologies. This area could thus become a near-term market oppommity for the DMFC, with transport uses being a longer-term goal, if further performance gains can be achieved.

Comparison of PEMFCs and DMFCs The PEMFC and DMFC have much in com-

mon, in particular their MEAs. The MEA and its components were described in detail in Part I (1). The MEA of a DMFC usually consists of five layers which include gas and liquid diffusion layers, and electrocatalyst layers with a polymeric proton conducting acidic membrane in between (2). The proton conducting membrane acts as an electronic insulator between the electrodes, but allows protons

Phfimm Metals Rev., 2002,46, (4), 146164 146

I

Fig. I The perjhnance losses seen in a typical DMFC MEA operuting with dilute MeOH and air at SOT, compared to those in a PEMFC. The PEMFC is operating with pure hydrogen. A list of furtors affecting the eflciencies of both .fuel cells i s on the right in the Figure

to migrate efficiently from the anode to the cathode. The membrane also functions as a physical barrier to prevent mixing of the reactants. In ad&- tion, a soluble form of the membrane m a t e d is used to impregnate the electrocatalyst layers to extend the membrane interface. This provides a proton conducting pathway.

While the structures of the MEAs used in the PEMFC and DMFC are similar, the performance of each is very different. A comparison of the performance of the two fuel cells and the factors which limit their efficiencies is shown in Figure 1.

The DMFC has a maximum thermodynamic voltage of 1.1 8 V at 25”C, dehned by its anode and cathode half-cell reactions:

Anode reaction: CH30H + H20 = COz + 6H’ + 6e-

E , = 0.046 v (i) Cathode reaction: 3/202 + 6H’ + 6e- = 3H20

E”, = 1.23 V (ii)

Cell reaction: CH3OH + HzO + 3/202 = COZ + 3H20 Encd = 1.18 V (ii)

In comparison, the PEMFC has a maximum thermodynamic voltage of 1.23 V at 25°C. In prac-

tice, the cell voltage in both fuel cells is much less than this, see Figure 1. For example, at a current density of 500 mA cm”, the cell voltage is typically around 0.75 V for the PEMFC (1) and 0.4 V for the DMFC (3). Therefore, the power density and efficiency are considerably hgher in the PEMFC (61 per cent) than in the DMFC (34 per cent).

The Effect of Poor Kinetics Both types of fuel cell are limited by the poor

electrochemical activiy of their cutbode-r, for reasons described in Part I (1). This reduces the cell voltage of both by up to 0.4 V at 500 mA

However, unlike the PEMFC (when operated with pure hydrogen), the DMFC anode is also h- ited by poor electrochemical activity (kinetic loss [8] in Figure 1). This can account for a further loss in cell voltage of more than 0.3 V at 500 mA cm-’ (at

To increase both the anode and cathode activities in the DMFC, the electrocatalysts employed are usually unsupported (with high Pt loadmgs of typically 5 to 10 mg Pt cm-’ for each electrode) rather than the carbon-supported electrocatalysts used in the PEMFC. This Pt loading is too high

900C).

Phtinnm MefaLr h., 2002,46, (4) 147

for commercial exploitation of the DMFC (but it does of course dramatically increase the power densities attainable by the MEA). By contrast, typical PEMFC electrodes are carbon-supported electrocatalysts, loaded at 0.2 to 0.5 mg Pt cm”.

Fuel Crossover Another critical effect, which reduces the effi-

ciency of the DMFC, is fuel crossover (methanol ~ J J O V W [4] in Figure 1). Methanol and water readily diffuse through all the commercially available polymeric membrane electrolytes (such as Nafion), and significant quantities of methanol and particularly water pass from the anode to the cathode. This reduces the cathode efficiency in two ways.

First, any methanol that comes into contact with the cathode electrocatalyst will reduce the efficiency of the oxygen reduction reaction by a competing electrochemical process - known as the mixed potential effect. Second, the cathode structure becomes waterlogged or flooded, and is no longer an efficient structure for gas diffusion (mars transport loss, [3] in Figure 1). Both these effects can reduce the cell voltage by a further 0.2 to 0.3 V, particularly when practical air flows are used.

In practice, the effects of methanol crossover can be reduced to a large extent by careful design of the MEA structure or by the application of novel membrane materials (4) or cathode electrocatalyst materials ( 5 , 6). The use of thick membrane materials, such as Nafion 117 (- 180 pn), in preference to those used in the PEMFC, such as Nafion 112 (50 q), is often a sensible choice. Using a thick membrane does increase the cell resistance (ehchu&e ndJtance [5] in Figure 1). but it is usually easily outweighed by an improved performance as a result of reduced crossover.

A further consequence of the high methanol crossover rates in commercially available materials is that to reduce it, the DMFC anode must be supplied with dilute methanol fuel, typically 0.5 to 1.0 molar concentration. This presents problems for system design because, in addition to the methanol fuel, large quantities of water must be stored, adding to the size and complexity of the system. It is particularly awkward for applications where space is limited, such as portable devices. As the

methanol concentrations used in the DMFC are low, the anode structure has to be designed to allow both efficient diffusion of the liquid fuel into the electrocatalyst layer and effective removal of the product carbon dioxide (COz). Correct design of the anode electrode spucture is very important for limiting anode mass iransportlosses ([GI in Figure 1).

Anode Electrocatalyst Limitations Although the electrooxidation of methanol is

thermodynamically driven (by the negative Gibbs free energy change, AG, in the fuel cell), in practice, the rate of methanol electrooxidation is severely limited by poor reaction kinetics. To increase the efficiency of the anode reaction, it is necessary to understand the reaction mechanism. Indeed, there are now probably over 100 published papers that deal with identifying the nature and rate limiting steps of this reaction (7).

The most likely reaction scheme to describe the methanol electrooxidation process is shown in Figure 2 (Steps i to viii). Only Pt-based electrocatalysts display the necessary reactivity and stability in the acidic environment of the DMFC. Spectroscopic studies on polycrystalline Pt have shown that methanol is electrosorbed in a complex process analogous to dehydrogenation. Sequential stripping of protons and electrons is believed to take place (Steps i to iv), leading to the formation of carbon-containing intermediates, such as linear- ly bonded - c o , d , and -CHO,d, (8, 9).

Although the vast majority of these studies have been carried out on bulk polycrystalline or single crystal metallic Pt surfaces, it is possible to study the methanol electrosorption process on finely divided electrocatalysts in a single cell. Methanol electrosorption appears to occur spontaneously when the anode and cathode of an MEA are connected externally by an electrical circuit. Hence, when methanol comes into contact with the electrocatalyst, an electric current flows between the two electrodes. This occurs for only a brief period of time until the electrocatalyst becomes poisoned with surface-bound intermediates, such as -CO,d,.

The results of an experiment in which three different anode electrocatalysts were exposed to a dilute methanol/water mixture are shown in

P h f h m Met& Rev., 2002, 46, (4) 148

Fig. 2 A reaction .scheme ilescribing the probable methntiol electrooxidutiorr process (Steps i to vii i) )tithin ( i D M F C titiode. Only Pt-bciscd electrocatalyst.~ show /he necessary reactivity rind sicrbility in the acidic environment of the DMFC to be ofprclcticnl use

Pt

Figure 3. The electrocatalysts were 40 wt.%

Pt/Vulcan XC72R carbon black, 20 wt.% Pt, 10 wt.% Ru/Vulcan XC72R and PtRu black alloy. The loadings on each electrode were: 1 mg Pt cm-* and 0.5 mg Ru cm-2 (ruthenium). Experiments were carried out at 90°C in a 50 cm2 in-house designed single cell using Nafion 112 membrane- based MEAs with Pt black cathodes (4 mg cm-*). The half-cell behaviour of the anode was studied by supplying pure hydrogen to the cathode, which then functioned as a reversible hydrogen electrode @HE) and also as a counter electrode.

Electrosorption was carried out under poten- tiostatic control at 75 mV (vs. WE) with a 2 M methanol solution for a period of 20 minutes. This potential was chosen because it is below the threshold potential at which the electrosorbed methanol would be electrooxidised to C02. The cell was then flushed with pure water for a further 20 minutes to remove any unreacted methanol.

As Figure 3 shows, a charge was produced by each electrocatalyst when it came into contact with

methanol (at - 400 s). The charge levelled out after a few minutes, suggesting that the electrocatalyst surface became poisoned and was unable to

Fig. 3 Three anode electroccitulysts (locrdings: I mg Pt em-', 0.5 nig Ru cni') in u single cell. with Nqfiorl 112 membrctne-based MEAs. exposed to dilute methanoUwter ( i t 90°C. The ccithodes are Pt bkrck (4 mg Pt en-'). At - 400 s after methanol contac/, the electroccrtcr1v.st.s produce charge which levels out rrs the su~cice becomes poisoned mid stops reacting. Cyclic voltammetry cmjirmed tin intermediate species was present

PLdnntn Metah b., 2002, 46, (4) 149

I Table I

I Surface Areas of Electrocatalyst Materials Pt and PtRu Determined with Gas-Phase CO and Electrochemically with CO and Methanol, and the Resulting Stripping Peak Potentials

Electrocatalyst surface area, m2 g" Pt or m2 g-' PtRu

Stripping peak potential, I Electrocatalyst

40 wt.% PtiXC72R 20 wt.% Pt, 10 Wt.% Ru/XC72R PtRu alloy black

co, gas-p hase

67 139 83

co, electrochemical

( E PSAco)

40 80 46

Methanol, electrochemical

(EPSAM~OH)

37 78 39

co, electrochemical

538 305 302

Methanol, electrochemical

react further with methanol. It was not possible to quantify the rate of t h i s reaction since a few seconds were required to pass the methanol solution through the flow field and across the entire area of the electrode. The presence of an intermediate species was confinned by ramping the anode potential up to 0.9 V (vs. RHE) at a scan rate of 10 mV s-'. This resulted in an electrooxidation peak (stripping peak) for each electrocatalyst, shown in Figure 4 (corresponding to Steps vi to viii in Figure

2). Water electrosorption is believed to occur leading to the formation of -OHdd, species which then react with the intermediate species to form COz (10,ll). This process results in the saipping peaks.

As the nature of the surface-bound intermediate was unknown but was believed to be 40- l ike , the experiments were repeated but with CO gas passing through the fuel cell instead of methanol. A CO,d,-stripping peak was recorded for each electrocatalyst, see Figure 4. In addition to the elec-

Fig. 4 Stripping peaks (electrosorbed methanol intermediates and electrosorbed carbon monoxide (CO(,'IJ) .for three mode electrocatalysts. The peaks probably correspond to Steps vi to viii in the reaction scheme of Figure 2

Phrinum Metab b., 2002,46, (4) 150

438 292 292

mv (vs. (RHE)

trochemical measurements, the gas-phase CO chemisorption areas of the electrocatalysts were determined. The data are summarised in Table I, and show the CO gas-phase and CO electrochemical surface areas for each electrocatalyst. The CO gas-phase surface areas correspond to the absolute maximum metal surface area. The electrochemically determined CO values, however, correspond to the electrode platinum surface area (EPSACO), which is the total metal area in contact with the proton conducting polymer in the electrode. For each electrocatalyst the EPS&O was less than the gas-phase value, indicating that not all the electrocatalyst in the electrodes was utilised.

Table I also summarises the EPSAMeoH values of each anode electrocatalyst, determined using the methanol electrosorption (or electrosorbate) stripping peak. (7%. dominant surface-bound intermediate was assumed to be Co&) These were found to agree well with the CO-stripping values (EPS&O) for the 40 wt.% Pt/XC72R and 20 wt.% Pt, 10 wt.% Ru/XC72R electrocatalysts. However, the values for the PtRu alloy black were somewhat different. A further difference was observed in the stripping-peak positions of each electrocatalyst, see Figure 4 and Table I. The Ru- containing electrocatalysts produced stripping peaks at much lower potentials than the pure Pt electrocatalyst, showing that the removal of the surface-bound intermediates was promoted by Ru. This is believed to occur more readily for PtRu alloys since Ru is more easily electrooxidised than pure Pt, and forms Ru-OHds at lower potentials (12). The -Had, species are then believed to spill over onto neighbouring Pt sites where they react with -Cods. This occurs at lower potentials than with pure Pt.

Another interesting observation was made con- cerning the relative positions of the methanol and -Codd, stripping peaks. For 40 wt.% Pt/XC72R the methanol stripping peak was observed at a lower potential (438 mv) than the CO stripping peak (538 mv). This could be an indication that the pure Pt electrocatalyst was not completely poisoned by the methanol, although the similar EPSA values from the methanol (EPSAM,,H) and CO (EPSAco) experiments make this debatable.

Further, the presence of a shoulder on both the methanol and CO Stripping peaks also suggests that the electrocatalyst contains either two types of reaction site or crystallites with differing activities that were resolvable by both techniques.

One final point to consider is the relevance of the EPSA values determined by each technique. Although the values in Table I are normalised for the Pt and Ru content of the electrocatalysts, it is not clear how the Ru components interact with CO in the gas-phase and in the electrochemical experiments. For example, the Ru (or Ru oxides) may not be covered with a complete monolayer of CO during the electrochemical measurements. This process is also probably strongly dependent on time, temperature and the partide size of the electrocatalyst. Similarly, the significance of the EPSA values determined with methanol are open to debate. Although methanol is believed to preferentially electrosorb on Pt sites, the process probably requires an ensemble of Pt atoms. Therefore, for complete poisoning, the methanol fragments must be mobile enough to release the Pt ensembles so further reaction with methanol can occur.

Nevertheless, the use of methanol stripping voltammetry appears to give an excellent indication of the available electrocatalyst surface area for methanol electrooxidation. This strongly comple- ments the measurements that are routinely carried out with co.

Better Anode Electrocatalyst Materials The search undertaken for more active anode

electrocatalyst materials for methanol electrooxidation in acid electrolyte is illustrated by studies similar to the one above. The electrocatalyst needs to provide both an efficient mechanism for methanol dehydrogenation and an efficient mechanism to electrooxidise - c o , d , to COZ.

Of great importance are materials that might combine with Pt to promote Steps iv to viii in Figure 2, and Ru in particular significantly increases the activity of Pt for methanol electrooxidation. Other studies have looked at elements that form binary alloys with Pt (Ru, Sn, Re, Au, Mo, W, Pd, R h (13-20)), and ternary (PtRuSn (21)) and

Phtinwm Metals Rev., 2002,46, (4) 151

-0- P t tXC72R -X- Pt lr lXC72R +- PtPdlXC72R + PtOstXC72R -A- PtRh IXC72R t PtRulXC72R -Xr PtWIXC72R +PtRuRhIXC72R 4 PtGalXC72R -.A.-PtRuSn/XC72R

0 0.1 0.2 0.3 0.4 0.5 0 6 0.7 0.6

SPECIFIC ACTIVITY, mA cfn-’ Pt

Fig. 5 Half-cell specific uctirity plots,fur Pt cilloy tnaterials in I M sulfuric acidR M methanol at 80°C shoning that Ru-conraining electrocutulysts ure the most cicrive. A lower mode potential corresponds to a more active electrocatalvst for methanol electrooxidution

quaternary alloys (P tRu I rOs (22)). At the Johnson Matthey Technology Centre,

the focus of DMFC anode development has been on using carbon-supported high surface area electrocatalysts. Figure 5 presents anode half-cell polarisation data for a series of Vulcan XC72R- supported Pt materials. These include pure Pt, and alloys of Pt with iridium (Par), palladium (PtPd), osmium (Ptos), rhodium (PtRh),. tungsten (PtW), gaUium (PtGa), ruthenium (PtRu), ruthenium- rhodium (PtRuRh) and ruthenium-tin (PtRuSn).

Steady-state measurements were performed at 80°C in 1 M sulfuric acid electrolyte containing 2 M methanol. Prior to the methanol electrooxidation studies, the in situ electrochemical metal area (ECA, m2 g-’ Pt) of each electrode was determined using CO stripping voltammetry. Unlike the EPSAco measurement, this value corresponds to the maximum available Pt surface area in the electrode. The sulfuric acid can make effective contact with the entire electrocatalyst surface because it floods the electrodes, as it also does in the gas- phase CO chemisoiption experiment. Thus, the performance of each electrocatalyst is not limited by electrode structure or by the EPSA effects that are seen in the MEAs. Using the ECA value for

each electrode, the half-cell polatisation data were corrected to give the intrinsic activity of the electrocatalysts (specific activity, mA cm-’ Pt). Hence, the activity of each anode electrocatalyst could be compared, independent of its surface area.

The half-cell data in Figure 5 show that the activities of the materials fall into two distinct bands. The most active electrocatalyst materials - those having the lowest potentials - all contain Ru. The elements Rh, 0 s and Ga appear to show pro- motional effects, but much smaller than that of Ru. Tungsten did not promote methanol electrooxidation on Pt, and Pd and Ir appeared to inhibit it.

The methanol electrooxidation activity of the PtRu was found to be the highest of the binary Pt- based alloys. A number of groups have claimed to

have developed ternary or even quaternary materials with activities higher than PtRu alloy (23, 24). The rationale behind some of these materials is sometimes unclear and quite often their new materials are compared with what could be considered a poor PtRu alloy baseline. Figure 5 also compares the methanol electrooxidation data of two ternary materials, PtRuRh and PtRuSn. Both Rh and Sn have been shown to promote the activity of Pt for methanol electrooxidation, but neither were found

PIatinrrm Met& Rm, 2002.46, (4) 152

to co-promote PtRu. This observation led to the conclusion that only modest improvements in the PtRu activity can be attained by addmg co-promoting elements. Indeed, quite often, adding ternary or even quaternary electrocatalyst components can reduce the production friendliness of the material and dramatically increase its cost. Hence, at Johnson Matthey, the electrocatalyst development work has focused on optimising the PtRu alloy.

An Optimum P1atinum:Ruthenium Ratio There are a number of published papers which

describe work to determine the optimum PtRu alloy composition for the DMFC anode (25, 26). For this type of study to be carried out successful- ly, the composition of the electrocatalyst must be controlled so that the surface structure is repre- sentative of the bulk alloy composition. (This can be challenging for carbon-supported electrocatalysts.) The composition of the electrocatalyst surface is determined by the chemical deposition process used to deposit the particles and/or by any post-treatment it receives, such as thermal annealing. The wide range of methods reported in the literature for preparing PtRu electrocatalysts therefore probably results in a range of materials with different surface compositions. This makes it difficult to assess which composition is most active for methanol electrooxidation. There is also evi- dence that different alloy compositions are favoured at high and low temperatures (27). Hence, it is probably only possible to select the most active PtRu alloy phase from a range of compositions prepared using the same deposition process and post-treatment conditions.

In order to determine the most active alloy composition for methanol electrooxidation, a range of PtRu/Vulcan XC72R electrocatalysts was prepared by an aqueous-based slurry route. Each electrocatalyst contained a 6xed Pt loadmg (20 wt.Yo); the Ru loadmg was varied to give a range of atomic compositions from PtlM to PtJtu,,. The preparation involved codeposition of highly-dispersed mixed oxide particles onto the carbon, followed by drying and heat treatment. Characterisation by X-ray difhction (XRD) was

used to estimate the bulk alloy composition (from the Pt lattice parameter) and the average crystallite size (using Scherrer’s equation (28)).

From Figure 6 (which shows some early work that used an experimental deposition technique) the bulk alloy composition and average crystallite size (as a function of alloy composition) can be seen. The XRD-determined bulk alloy compositions shown here are a reasonable match to the theoretical compositions. Alloys PtwRulo and Pt&uzo had bulk alloy compositions identical to the theoretical compositions, but alloys from Pt7oRu~ to Pt&u,O appeared to be Pt-rich. Thus, part of the Ru was not being incorporated into the predominant crystalline face centred cubic (f.c.c.) PtRu phase but was present either in an amorphous Ru oxide phase or in an amorphous Ru-rich PtRu phase - but neither of these phases could be detected with XRD. X-ray photoelectron spectroscopy (XF’S) measurements suggested that the electrocatalyst surface was indeed Ru-rich.

The XRD crystallite size data showed an interesting effect: the crystallite size of P t l m was very large (- 12 nm) but fell dramatically as the Ru content was increased to 30 at.% and above. The crystallite size of alloys with theoretical compositions between Pt70Ru~ and P ~ ~ O R U ~ ~ was found to be between 2 to 3 nm. This suggests that Ru promotes the dispersion of the electrocatalyst. The effect was most noticeable for materials having

Fig. 6 XRD dutu j b r a range af’PtRdYC72R electrocutu1y.st.s. showing cilloy composition cmd uverage ctystallite size. The diagonal dushed line represents the theoreticul cornpodion. These mciteriuls were used to assess the suitahilir?. of a new laboratary-.sccile chemicul deposition process

Pkadnwm Metah Rey., 2002,46, (4) 153

compositions (Pt&uW to Pt&u7,,) which deviated most from the theoretical composition. Therefore, the unalloyed amorphous material that may reside on or near the surface of the PtRu alloy particles may help prevent sintering during the deposition or thermal reduction processes. For alloys Pt&ulo and PtsoRuzo this effect was less prominent because all the Ru was incorporated into the bulk alloy.

To investigate the surface electrochemical behaviour of the PtRu alloy electrocatalysts and their activities for methanol electrooxidation, all the electrocatalysts were used to prepare electrodes suitable for testing in sulfuric acid electrolyte. Aqueous-based Nafion ionomer inks were prepared and carbon-fibre paper electrodes were manufactured using a coating process.

Figure 7 shows the half-cell methanol electrooxidation activity and the ECA (mz g-' PtRu, determined with CO-stripping voltammetry) for each PtRu material. The methanol electrooxidation activities were determined in 1 M sulfuric acid and 2 M methanol at 80°C. The electrodes contained 0.35 mg Pt cm-'. The methanol electrooxidation activity is compared at a mass activity of 100 mA me-' Pt; electrocatalysts with lower anode potentials were the most active. (The mass activity corresponds to the current density corrected for the electrode Pt loading.) As expected, pure Pt was

Fig. 7 Electrochemical dutu recorded in u hulfcell for PtRu ullovs in I M suljirric acid. The effect of the PtRu ulloy compohition is shown on: ( i ) methunol electrooxidotion uctivit?, at 100 mA mg-' Pt und 80°C in 2 M MeOH; (ii) the ECA (m' g ' PtRu) determined with CO stripping voltummetry ut u sweep rute .f I0 mV s I :

(iii) the 1-ulculuted totul electrochemicul nietul ureu (m' g ' PtRu) from the XRD cnwullite size

the least active material, requiring an anode potential of - 0.500 V (vs. RHE). However, its activity increased dramatically as the Ru content was increased to Pt70Ru,o, but at higher Ru contents the activity became constant at - 0.340 V (vs. RHE).

Figure 7 also shows the theoretical (calculated from XRD data assuming spherical particles) and electrochemical (from CO-stripping voltammetry) metal surface areas as a function of alloy composition. The two sets of values compare well; the ECA values of Pt3oRu70 to Pt&uN are the hghest.

An examination of the data suggests that two effects may control the activity of the electrocatalysts. First, as the level of Ru was increased in the alloy to 30 at.% and above, the ECA of the electrocatalyst increased. The XRD data also suggest that part of the Ru was not incorporated into the Pt lattice but may have remained segregated on the surface of the particles, perhaps as an oxide. Further addition of Ru beyond Pt~Rum did not lead to a relative increase in the amount incorporated into the Pt lattice. Instead, the amount of unalloyed Ru remained essentially the same (as shown by the constant deviation of the XRD alloy composition versus the theoretical composition in Figure 6). Thus, the methanol electrooxidation activity of all these materials is roughly similar. It appears that good alloying of Ru into the Pt lattice

Plalinwm Met& Rev., 2002,46, (4) 154

I Table I I

Composition

20 Wt.% Pt, 10 Wt.% RU 40 Wt.% Pt, 20 Wt.% RU PtRu black Pt black

I Some Physical and Electrochemical Parameters for Pt Black and Various PtsoRuso Alloy Electrocatalyst I ComDositions

XRD crystallite XRD lattice Calculated surface CO chernisorption metal size, nm parameter, 8, area, rn2 g-' Pt(Ru) area, ECA, m2 g-' Pt(Ru)

1.9 3.877 174 139 2.5 3.883 132' 104 2.9 3.882 114 83 6.5 3.926 43 24

is required to produce an active electrocatalyst, but that the process of 'tilling the Pt lattice' may also enable a stable surface Ru component to be built up - most likely essential for promoting methanol electrooxidation (1 2).

This contrasts with the proposed mechanism by which PtRu alloy promotes CO tolerance in the PEMFC at practical anode potentials. The CO tolerance (in PEMFCs) of PtRu is believed to occur because the incorporation of Ru in the Pt lattice decreases the Pt-COd, bond strength, reducing the -Codd, coverage (28). Surface Ru only comes into play at hgher potentials where it promotes -co& electrooxidation. as in the DMFC.

Anode Electrocatalyst Structure Unsupported PtRu alloy blacks are the most

widely used electrocatalysts employed at the DMFC anode, primarily because they provide very high Pt loadings (210 mg Pt cm") to maximise the EPSA in the electrode. Such electrodes are very active for methanol electrooxidation but are too expensive for most commercial applications.

To investigate whether the metal h d n g could be reduced to a more economical level and find the effects on performance, a series of PtRu alloy electrocatalysts of composition Pt&uw was prepared. The materials were PtRu black (HiSPEC" 6000), and two Vulcan XC72R-supported electrocatalysts of composition 20 wt.% Pt, 10 wt.% Ru (HtSPECm 5000) and 40 wt.% Pt, 20 wt.% Ru. The crystallite sizes and lattice parameters were determined by XRD, see Table 11. The smallest crystallite size was 1.9 nm for the 20 wt.% Pt, 10 wt.% Ru electrocatalyst. The 40 wt.?? Pt, 20 wt.%

Ru electrocatalyst had a slightly larger crystallite size (2.5 nm), while the PtRu black had the largest (2.9 nm). These are excellent dispersions, especia- ly for the latter two, and this is very apparent when their crystaJlite sizes are compared to that of unsupported Pt black (6.5 nm) (HLSPECTM 1000).

The improved dispersions found for PtRu electrocatalysts compared with a pure Pt electrocatalyst at a similar loading on carbon was described in Part I1 (29). The presence of Ru again appears to promote the dispersion, most probably through small amounts of surface-segregated Ru oxides (or surface enrichment with Ru) which prevent sintering. The XRD lattice parameter values for each PtRu electrocatalyst also show a shift from the value for pure Pt black. This is not indicative of exactly PtsoRuso alloy but of slightly Pt-rich alloy (compared to the theoretical composition).

The CO chemisorption metal areas c o n k e d the trend seen in the XRD crystallite size data. The CO gas-phase area of 20 wt.% Pt, 10 wt.% Ru was the highest (139 mz g-' PtRu); slightly lower (104 mz g-' PtRu) for 40 wt.% Pt, 20 wt.% Ru; and lowest (83 mz g-' PtRu) for PtRu black alloy, although this last value is much higher than that of the Pt black (24 m2 g-' Pt). The difference between the calculated and CO gas-phase areas is probably due to obscuring of the metal crystallites, and was very evident for the Pt black sample.

Specific Activity for Methanol Elcctrooxidation To find the methanol electrooxidation activity

of the electrocatalysts, flooded steady-state half- cell experiments were performed in 1 M sulfuric acid and 2 M methanol at 80°C. Electrodes were

Phfinnm Metals h., 2002,46, (4) 155

Fig. 8 Flooded anode half-cell polarisation dafu ut 80°C in I M sulfuric a c i d n M methuno1,for three PtRu materials with a Pt loading of - I mg Pt cm '. The intrinsic activity of each material was cornparable under these conditions

prepared using electrocatalyst-containing aqueous Nafion inks, with a loacllng of - 1 mg Pt cm-'. Figure 8 shows the specific activities of the three PtRu electrocatalyst materials; under the reaction conditions, the methanol electrooxidation activities were comparable. That is, the intrinsic kinetic activity of the electrocatalysts was unaffected by the electrocatalyst structure and no significant electrode structure effects were observed. The lack of electrocatalyst structure effects is probably due to the sulfuric acid electrolyte penetranng the entire electrode structure, and utilising all the electrocatalyst.

MEA Anode Performancc

To study the effect of the anode electrode structure on the MEA performance, a series of experiments was carried in a 3 cmz micro-fuel c d .

The electrodes described above (with 1 mg Pt cn-3 were used to prepare MEAs using Nafion 112 membrane and Pt black cathodes (4 mg Pt cm-2).

Figure 9 shows the results of pseudo anode half-cell (or half MEA) experiments at 90°C. In these experiments, the anode of the MEA was supplied with 2 M methanol fuel and the counter electrode with pure hydrogen. The fuel cell was then driven by a potentiostat and the anode potential (vs. RHE) was measured as a function of the current density. The resistance of the MEA was determined using current-interrupt techniques.

Although the intrinsic activities of the electrocatalysts had been identical in sulfuric acid electrolyte (Figure 8) this was not the case when these electrocatalysts were employed in the anode of an MEA. Within the MEA, their anode performance appears to be linked to a number of factors

Fig. 9 Pseudo anode halfcell (or half MEA) experiments at 90°C. The anode potential (w. RHE) is measured as afunction qj'current densip,for the three PtRu muterials. 2 M Methanol was supplied to the anode and pure hydrogen to the cathode. The 40 wt. % Pt, 20 wt. % Ru electrocatalyst had the highesr performance, shown b?j its lower potential

Ph%imm Me& Rev., 2002,46, (4) 156

Fig. 10 Single cell polurisation curves showing the effect of the anode structure on the MEA performance. The highest anode perforniance is given by 40 wt.% Pt, 20 wt.% Ru. The anode loading is I m g Pt c t d . The operating temperature is 90°C, and Najion I I7 membrane is used. The fuel is 0.75 M MeOH

The cuthodes are bused on Pi black (4 m g Pt ern-’ ) ond the oxidant is pressurised air (30 p i g , L,,w = 5)

( A h f < O H = 4.5).

including electrocatalyst udisation (the extent of the electrocatalyst/ionomer interface), the thickness of the electrocatalyst layer and its porosity.

The anode containing the 20 wt.% Pt, 10 wt.%

Ru electrocatalyst had the lowest performance of the three anode electrocatalysts, see Figure 9. This anode had the highest EPSA (EiPSAMdH = 78 mz g-’ PtRu) but corresponded to the thickest electrode layer (at 1 mg Pt crn-’)). Its performance suggests it was suffering from mass transport limitations at current densities > 200 mA cm-’. It seems that methanol could not enter the entire structure and COZ could not escape. At current densities > 1000 mA cm-’ th is was particularly severe.

This observation suggested that the PtRu black should have the best performance of the three materials as it produced the thinnest electrocatalyst layer, but this is not the case. The PtRu black anode has a significantly better performance only at high current densities (> 1000 mA cm-’). At low current densities, when kinetic control is attained, the performances of the PtRu black and 20 wt.%

Pt, 10 wt.% Ru anodes were almost identical. (Kinetic control is attained when mass transport does not occur and only electocatalyst kinetics limit performance.)

In fact, the 40 wt.% Pt, 20 wt.% Ru electrocatalyst had the hlghest performance of the three over the complete range of current densities. This electrocatalyst seems to produce the best compro- mise between available electrocatalyst surface area

(when operating in the MEA) and electrocatalyst layer thickness (to minimise mass transport losses). At a current density of 500 mA cm-’ (corresponding to an anode potential of 0.35 V (vs. M E ) ) its potential was about 30 mV lower than that of the PtRu black electrocatalyst and more than 50 mV lower than that of the 20 wt.%

Pt, 10 wt.% Ru electrocatalyst. This is an excellent performance with none of the mass transport limitations shown by the 20 wt.% Pt, 10 wt.% Ru electrocatalyst. The reason for its superior performance over PtRu black is not easy to explain.

One aspect is the EPSA; the 40 wt.% Pt, 20 wt.% Ru electrocatalyst has a higher available EPSA (EPSAM,oH = 59 m’ g-’ PtRu) than the PtRu black (EPSAM,oH = 39 m2 g-’ PtRu). However, EPSA values should only at best be considered as corresponding to the maximum accessible electrocatalyst surface area. In operation the actual active surface area of the anode may be lower than the EPSA value or may change dynamically with CUT-

rent. The real udisation of the 40 wt.% Pt, 20 wt.% Ru electrocatalyst may therefore be significantly %her than that of the PtRu black.

Following the micro-fuel cell experiments, MEAs of area 50 cmz were prepared with the same anode and cathode electrodes as before but th is time with Nafion 117 membrane (instead of Nafion 112), see Figure 10. The resulting MEAs were tested in a DMFC single cell at 90°C. Methanol fuel (0.75 M) was supplied to the anode of the MEA at ambient

Piatinurn Metah REV., 2002,46, (4) 157

pressure and at a flow 4.5 times in excess of stoichiometry = 4.5) (a stoichiometry of 1 is the amount needed to sustain the current). The cathode was supplied with unhumidified air at a pressure of 30 psig at a flow 5 times stoichiometry

The data in Figure 10 show the same clear trend as the pseudo anode half-cell data in Figure 9. The MEA containing the 40 wt.%, Pt, 20 wt.% Ru electrocatalyst gave the highest performance (0.5 V at 228 mA cm-’) compared with 20 wt.% Pt, 10 wt.%

Ru (0.5 V at 170 mA ern-') and PtRu black (0.5 V at 187 mA cm-’); all had the same Pt loading of 1 mg Pt cm-’. Figure 10 also gives current-interrupt resistance data for the same series of MEAs, also showing that the structure of the anode did not influence the resistance of the MEA. That is, the performance difference was entirely due to the change in anode structure.

Therefore it appears that 40 wt.% Pt, 20 wt.%

Ru gives an MEA performance superior to those of 20 wt.% Pt, 10 wt.% Ru and PtRu black. Excellent single cell performance have been attained with MEAs containing only 1 mg Pt cm-’ with power densities exceeding 100 mW cm-’. This shows that careful choice of the anode structure is important to maximise DMFC MEA performance and that the levels of PtRu electrocatalyst can be reduced significantly fiom the 2-10 mg Pt cm” levels that are traditionally employed.

The Effect of Membrane Thickness

(L = 5).

Nafion 117 membrane is the preferred electrolyte for the DMFC. It is the thickest (- 180 p) available commercial fuel cell membrane. The rate of methanol crossover through Nafion 117 is low compared to, for instance, the thinner Nafion 112 membrane (50 p). New membrane materials to help reduce the methanol crossover rate are being developed, but it is unlikely that any of the current candidates will

completely eliminate it as all low-temperature proton conducting polymer materials only function efficiendy in a fully hydrated state. Methanol, being completely miscible with water, is carried by the water as it diffuses through the membranes.

In the PEMFC, thinner membrane materials (such as 30 p) are preferred as they offer reduced

ionic resistance and thus increased MEA performance. They also help to reduce the MEA cost. For the DMFC, it would be advantageous to use thinner membrane materials to reduce the ionic resistance of the MEA. However, there is a sensible lower thickness limit beyond which the rate of methanol crossover becomes too hgh and/or the membrane is no longer strong enough to maintain the large pressure differentials often needed.

Cathode Improvements With careful design of the cathode, it has been

possible to use Nafion 112 membrane as an alternative to Nafion 117, without significant loss in performance. Data from a 50 cmz single cell containing MEAs with Nafion 117 and Nafion 112 membranes is shown in Figure 11. Both MEAs contained a 40 wt% Pt, 20 wt% Ru (1 mg Pt ad) anode and a Pt black (4 mg Pt cm-’) cathode. Cell voltage data were recorded at 90°C with 0.75 M methanol ( 1 ~ 4 ~ = 4.5) and pressurised air (30 psig, h, = 5). In a second (pseudo half-cell diag- nostic) experiment, the anode potential was determined by passing pure hydrogen across the cathode (instead of air) and the fuel cell was driven by an electric load. Hence, the anode and cathode potentials could be decoupled from the cell voltage. Current-interrupt measurements were used to determine the MEA resistance.

Under these conditions, the MEA with Nafion 112 had the better performance than with Nafion 117, especially at lugher current densities. This was shown to be mainly a resistance effect - the resistance-corrected data for both MEAs were comparable (except that the cell voltage of the Nafion 112 MEA was about 10 mV lower at low current densities, probably due to enhanced methanol crossover). This observation was con- firmed by the anode and cathode half-cell data for the MEAS. As expected, the anode half-cell potentials of both MEAs were very similar. In the Nafion 112 MEA the cathode potential was only about 10 to 20 mV lower than in the Nafion 11 7 MEA due to the enhanced crossover rate through the thinner membrane.

Figure 11 also shows the cathode potential for the same Nafion 112 MEA when it was operating

Phfinum Met& Rcv., 2002,46, (4) 158

Fig. I I A comparison of Najion 117 and Najion 112 membranes in MEAT. Both MEAs hove (I 40 wt.% Pt, 20 wr.% Ru anode ( I mg PI cni ') and a Pt black cathode (4 mg Pt cm-'). The data were recorded in a 50 cm2 single cell at the operating temperature of 90°C with 0.75 M methanol,fuel (LOU = 4.5) and pressurised air (30 p i g . A,,, = 5). hi a pseudo halj-cell experiment, pure hydrogen was pussed across the cathode to help determine the mode potential. The Nujiori 112-bused MEA had the higher performance (especially at higher current densities) due to reduced membrane resistance

as a PEMFC. Instead of methanol and dry air, it was supplied with humidified hydrogen and humidified air, respectively, (both at 30 psig). The cathode potential in PEMFC-mode is only slightly higher (10 mv) than in DMFC-mode (but is slightly lower than the cathode potential for the Nafion 117 MEA in DMFC-mode). This suggests that the Pt black-based cathode structure used in these MEAS has good methanol tolerance and indicates that the cathode structure can be optimised to make it essentially methanol tolerant. However, these experiments were carried out with relatively high air flows (hk = 5) and at high pressures which reduce the effects of crossover to some extent.

Reducing the Cathode Air Flow

The air flow rate in the single cell shown in Figure 11 is too high for most practical fuel cell applications (large volumes of air require energy to

pressurise them). The cathode exhaust gas from the fuel cell stack must also be cooled efficiently to remove any methanol (from crossover) and water vapour. This places a high energy demand on the fuel cell system. A lower air flow, preferably equiv- dent to a stoichiometry of 2 (A- = 2) or less, is thus desirable.

Figure 12 shows the performance of a Nafion 117-based MEA, of similar construction to that in Figure 11. Single cell measurements were carried out at 30°C with 0.75 M methanol fuel ( ~ M , O H = 4.5) and pressurised air (30 PSI&, but at the lower air flow rate, h, = 2. Under these conditions, the MEA performance w a s very similar to that of the MEA in Figure 1 1 which was operating with a hgh

Pseudo half-cell experiments were carried out to decouple the anode and cathode half-cell potentials in the MEA. The cathode potential was found

air flow (L = 5).

Phtimm M e f d b., 2002,46, (4) 159

Fig. 12 Data recorded at low airflows to the cathode.

cell with a Nafion I1 7 MEA. The anode is 40 wt.% Pt, 20 wt.% Ru ( 1 mg Pt cm-') and the cathode is platinuni bkrck (4 mg PI cnii'). The operating temperuture is 90°C und the,fuel supplied to the anode is 0.75 M methanol (LOH = 4.5); the nir is pressurised (30 psig). The cell perjhnance under the low airflow conditions is compunible to that at higher air,flows. This demon.strutes the good methanoWwuter tolerance of the cathode

= 2, in n 50 cm' single

to be only 5 1 0 mV lower under the low air flow conditions, showing the excellent water and methanol tolerance of the cathode. The cathode potentials were also compared in DMFC- and PEMFC-modes, and were found to be identical under the low air flow condition. Thus, the effects of methanol crossover can be significantly reduced by careful design of the cathode and the performance can be maintained at low air flows. Indeed, methanol-tolerant materials (6) may not be required under these conditions, especially with Nafion 11 7 membrane.

Reducing Cathode Electrocatalyst Loading The DMFC anode electrocatalyst developments

described so far have been aimed at reducing the Pt loading to 1 mg Pt ern-', while maintaining performance. This has been achieved with 40 m.% Pt, 20 wt. YO Ru/Vulcan XC72R. By comparison, in the PEMFC the typical Pt electrocatalysts used in the cathodes are also supported on Vulcan XC72R, but the loading is only 0.2 to 0.7 mg Pt cm-2 which gives an excellent MEA performance (1). AU the DMFC single cell data described here

have used MEAs containing high loaded cathodes

(Pt black, 4 mg Pt cm-2). To reduce this loading, work was undertaken to develop carbon-supported Pt electrocatalysts of much hgher surface area than Pt black electrocatalyst (24 mz g-' Pt) (1). A reduction in Pt loading from 4 to 1 mg Pt cm-2 was investigated, and providmg that the methanol tolerance is comparable to that of Pt black, no impact on performance was expected. The new materials must also be able to cope with the high levels of water and methanol found at the DMFC cathode.

In Figure 13, data from a 25 cm2 single cell measured at 90°C for three MEAs is shown, one is based on Pt black (4 mg Pt cm-') and two are based on carbon-supported Pt cathodes (1 mg Pt cm-'). Methanol (0.5 M) was supplied to the anode

= 3) and pressurised air to the cathode (30 psig, h, = 10). Cathode A was based on 40 wt.%

Pt on carbon @CA 60 m2 g-' Pt) of similar construction to that used in the PEMFC. Cathode B was based on a 60 wt.% Pt on carbon (ECA 45 m2 g-' Pt) and was optimised for DMFC operation. The performance of the MEA with cathode A was slightly lower than the Pt black cathode. The MEA with cathode B performed comparably to the Pt black cathode, showing that the cathode Pt loadmg

Platinnm Metalr Rev., 2002,46, (4) 160

Fig. 13 Cell voltage data recorded in u 25 cm' single cell of the performances of three MEA cathodes at u 90°C operating temperature. The Pt black cathode is loaded at 4 mg Pt cm-'. Cathode A (40 wt.% Pt/ carbon) and Cuthode B (60 wt.% Pt/carbon) are loaded at I mg Pt cm '. Methanol fuel (0.5 M ) was supplied to the anode (b,.,~ = 3). und pressurised uir (30 p i g ) to the cathode at high flows (A",, = 10). The anode was 40 wt. % PI, 20 wt.% RulXC72R (1 rng f t cm ')

can be reduced significantly without performance loss. Further optimisation is expected to bring the Pt loading to the levels used in the PEMFC.

Portable DMFC Applications Recently, the tremendous advances attained in

power densities by the DMFC have prompted companies, such as Smart Fuel Cell (Germany); Manhattan Scientific, MTI and Motorola (U.S.A.); and Toshiba gapan) to establish ambient micro- DMFC programmes to target the 1-100 W power range. While the power densities offered by the DMFC are considerably less than those from the PEMFC, the DMFC can still generate sufficiently high energy densities to make it an attractive alternative to secondary batteries for a wide range of applications. Miniaturisation of the DMFC system is also simpler. With liquid fuel, the main advantage is the convenience of almost instant recharging, by replacing a spent fuel cartridge - an advantage over rechargeable batteries. The DMFC is therefore being targeted at applications such as mobile phones, notebook computers and video cameras where rapid recharging is advantageous.

To date, the most efficient DMFC systems are almost all exclusively designed to operate at hgher temperatures and pressures where the power densities are the hghest. Most MEA development has focused on increasing the performance in the temperature range 80 to 130°C and little work has

been done to increase the MEA performance at lower temperatures and pressure (20 to 60"C, ambient air pressure). Often, the MEAs used in portable ambient DMFC systems have been optimised for higher operating temperatures and pressures, which may not be the best option to maximise power density. Tailoring the MEA components, including the electrocatalysts, substrate and membrane, may improve the performance further and is a hgh priority for device developers, as improvements in the stack power/size ratio will allow more straightforward miniaturisation.

Miniaturising the Fuel Cell Stack

Figure 14 presents 50 cmz single cell data for an MEA based on Nafion 117 membrane, a 40 WL%

Pt, 20 wt.% Ru/XC72R anode (1 mg Pt cm-') and a Pt black cathode (4 mg Pt cd). The data were measured at 40,60 and 80°C with 0.5 M methanol (flow rate 6 ml mid) and ambient air (< 0.3 psig inlet pressure) at low flows (L = 2). Although this MEA was optimised for hqgher temperatures and pressures, its performance under low pressure conditions was good. The data is summarised in Table In together with projected fuel cell stack volumes (cm') for a range of devices.

The fuel cell stack volumes were calculated based on a 3 mm cell pitch (the thickness of one bipolar flow field plate and one MEA), 10 mm thick stack end plates and an MEA membrane

Platinum Metah Rev., 2002, 46, (4) 161

Fig. 14 Single cell data for an MEA based on Nufion 117 with an anode of 40 wt.% Pt, 20 wt.% RdXC72R ( I mg Pt cm") and a Pt black cathode (4 mg PtT The temperatures were 40, 60 and 80°C with 0.5 M methanol fuel supplied to the anode (flow rate 6 ml mini') and ambient air (< 0.3 p i g inlet pressure) at flows (a,,,= 2 ) to the cathode. At 40°C the cell voltage was 0.409 V and power density 21 mW cm-2; at 60°C the cell voltage was 0.419 V and power density 42 m W crn-'; and at 80°C the cell voltage was 0.440 V and power density 66 m W cm

border of dimensions 5 mm x 5 mm x 5 mm x 10 mm for edge sealing (the 10 mm dimension includes provision for porting - the holes cut into the membrane to allow the gases and liquids to flow). The calculation does not include the volume of the fuel pump, the air blower or the fuel tank. The projected stack volumes are based on the power density of the MEA increasing by a factor of two.

The htst example in Table I11 shows, that to generate 1 W of power at a stack voltage of 3.6 V (typical cell phone requirements) when operating at N"C, 9 MEAs of active area 5.4 cm2 are required, giving a projected stack volume - 63 cm3 - far too large to fit a modern cell phone. Doubhg the power density produced by the MEA would only modestly reduce the stack volume to - 42 cm3 because the end plates and MEA edge seals are responsible for a large proportion of the stack volume. This demonstrates that miniaturisation of the DMFC to fit a cell phone will be challenging.

The other examples shown in Table III correspond to larger 30 W 10 V devices operating at 40, 60 and 80°C. The larger devices utilise volume more effectively, primarily because the end plates and edge seals represent a much smaller propor-

tion of the overall volume of the stack. When operating at 4O"C, the projected stack volume based on current MEA technology is 823 cm3 (requiring 24 MEAs of active area 61 cm'). If the temperature of the fuel cell stack is increased to 60 and 80"C, the volume of the stack decreases to 430 and 334 cm3, respectively. Temperature thus has a large effect on stack volume. When the temperature is increased from 40 to 60°C the stack volume almost halves. The stack volumes are very attractive; when operating at 60"C, the approximate dimensions of a 30 W 10 V stack would be 5.5 cm x 5.5 cm x 14 cm. When operating at 40"C, with a doubled MEA power density, the projected stack volume is again significantly reduced from 823 to

441 cm3. At 60 and 80"C, the impact on the stack volume is less marked, decreasing from 430 to 261 cm3 and from 334 to 191 cm3, respectively. Again, these are very attractive stack volumes and show why the DMFC is being rigorously developed as a secondary battery replacement device.

Extending Upper Temperature Limit While the power densities produced by low

temperature ambient pressure DMFC stacks have become attractive enough to drive its near term

PUnum Metals h., 2002,46, (4) 162

em-2

Table Ill Ambient Pressure DMFC MEA Performances and Fuel Cell Stack Dimensions*

Stack power, W

1

30

30

30

Stack voltage,

V

3.6

10

10

10

MEA active area,

cmz

5.4 (2.8)**

61 (31 )

30 (1 6)

20 (11)

* Data r im u 50 cm' single cell for an MEA based on Na&m 117 memhmne with on anode of 40 wt.% PI, 20 wt.% Ru/XC72R ( 1 m g Pt cn- j and a PI block ruthode (4 mg Pt em-')). Methanol fuel 0.5 M (flow rate 6 ml m i d ) is supplied to the anode and ambient air (< 0.3 psig inlet pressure) orflow (&,,, = 2 ) is supplied to the cuthode. "This value and 011 other volues in brackets are projections based on increasing the power density of the MEAs by a,fucror of two

f

Cell Power Stack voltage, density, volume,

V m W c m 2 cm3

0.409 20.5 63 (0.409) (40) (42)

0.409 20.5 823 (0.409) (40) (441 1

(0.419) (80) (261)

(0.440) (1 20) (191)

0.41 9 42 430

0.440 66 334

commercialisation, some argue that longer term transport applications should be targeted. The DMFC system, and the reformer-PEMFC system, are considered to be good options for transport uses, but the DMFC efficiency is poor compared to the PEMFC. On the other hand, the PEMFC stack must be humidified so the hydrogen (refor- mate) and air are saturated with water vapour. Without humidification the MEA will dry out and eventually fail due to resistive heating and pin-hol- ing of the membrane. In addition, the large

amounts of low grade heat must also be removed from the stack and radiated to the surroundmgs. However, the size resmctions, for example, of an automobile make this difficult to achieve effectively, and has led some to believe that the fuel cell stack operating temperature must be increased beyond 100°C. Heat management would then be less critical.

This presents an ideal opportunity for the DMFC, with its dilute methanol fuel solution providmg it with the necessary humidification. The

Fig. 15 The effects of operating temperatures 90 und 130°C on u DMFC single cell with a Narfion II 7-based MEA. The anode is 40 nit. % Pt. 20 wt. % Ru ( I mg Pt cmn ')); the cathode is Pt black (4 mg Pt ern-'). Pressui-ised air (30 p i g ) jlows (L = 2 ) to the cathode and 0.75 M methanol = 4.5) is supplied to the anode. At 90°C the MEA perfortnunre is - 330 mA c111i~ at 0.5 V A! 130°C the MEA performance is - 530 mA mi2 at 0.5 V (or 500 mA cn-' ut 0.510 V ) I

PIatinum Metals b., 2002,46, (4) 163

Stack temp.,

O C

40

40

60

80

Current density, mA cm-'

50

50

100

150

Number of MEAs in stack

9

24

24

23

MEA active area,

cmz

5.4 (2.8) **

61 (31 )

(1 6)

20 (11)

30

large volumes of water circulated around the stack help to keep the membrane humidified at temperatures where the PEMFC membrane could not operate.

Figure 15 presents DMFC single cell data for a Nafion 117-based M E A employing 40 wt.% Pt, 20 wt.% Ru anode (1 mg Pt cm-’) and a Pt black catt- ode (4 mg Pt cm-’). The design of the MEA is more advanced than previously presented. It is supplied with 0.75 M methanol @,McOH = 4.5) and pressurised air at low flows &,, = 2). At 9O”C, the h E A performance is - 330 m A cm-2 at a cell voltage of 0.5 V, which is significantly higher than presented earlier. Due to the advanced design of the MEA, its performance increases dramatically at hgher temperature. Hence, at 130°C the performance was about 530 mA m-’ at 0.5 V (or 500 mA cm-’ at 0.510 V). The current-interrupt resistance was found to be unchanged at 130°C showing that the MEA was well humidified.

This level of performance brings the DMFC much closer to that of the PEMFC and strongly suggests that with further modest improvement in power density, the DMFC system could success- fully compete with the reformer/PEMFC system.

Acknowledgements The financial assistance of the EU is acknowledged, under

the framework of the Non-Nuclear Energy Programme Joule III Contract, JOE3-ClY5-0025. The contributions of past and present members of the Johnson Matthey fuel cell research group are acknowledged: S. Ball, N. Collis, S. Cooper, J. Denton, D. Fongalland, M. Gascoyne, K Goodman, H. G. C. Hamilton, G. A. Hards, K L. Hogarth, G. Hoogers, J. Keatmg, D. Lonergan, D. Peat, E. Smith, B. Theobald, D. Thompsett and N. Walsby.

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25 W. H. Lizcano-Valbuena, V. A. Paganin and E. R Gonzalez, Ekctmbim. Acta, 2002,47, (22-23), 3715

26 H. N. Dinh, X Ren, F. H. Garzon, P. Zelenay and S. Gottesfeld, J. Ekctmand Cbem., 2000,491, (1-2), 222

27 H. A. Gasteiger, N. Markovic, P. N. Ross and E. J. Cairns, J. Ekctmchem. Soc., 1994,141, 0, 1795

28 P. W. Atkins, “Physical Chemistry“, 4th Edn., Oxford University Press, 1990, p. 622

29 R Ralph and M. P. Hogarth, Pkdnnm Metah Rm, 2002, 46, (3), 117

The Authors Martin Hogarth is a Senior Scientist at the Johnson Matthey Technology Centre and has worked in the area of DMFCs since 1992. His main interests are the development of new electrocatalyst materials and high-performance MEAs for DMFCs. He is also interested in novel high-temperature and methanol- impermeable membranes for the PEMFC and DMFC, respectively.

Tom Ralph is the Head of Electrochemical Engineering at the Johnson Matthey MEA manufacturing facility based at Swindon. His main interests are the development of MEAs for PEMFC and DMFCs.

Platinwm Metah Ray., 2002,46, (4) 164

The Chemistry of the Platinum Group Metals A REPORT OF THE EIGHTH INTERNATIONAL CONFERENCE

By John Evans Department of Chemistry, university of Southampton, Southampton SO17 1 BJ, U.K.

The themes of the Eighth International Conference of the Chemistry of the Platinum Group Metals (PGM8), held at the University of Southampton, from 7th to 12th July 2002, covered a broad spectrum from the chemistry of these fascinating elements, ranging through

Organometallic chemistry Coordination and supramolecular chemistry Biological and medicinal chemistry Surfaces, materials and crystal engineering Photochemistry and electrochemistry

9 Catalysis and organic syntheses, to Theoretical chemistry and physical methods. The attendees also found time to cruise down

Southampton Water (in mist and rain), visit Stonehenge and Salisbury (only a little rain), walk through in the New Forest (totally dry!), and dine under Kmg Arthur’s Round Table in the Great Hall in Winchester.

But the open and challenging atmosphere was the most apparent hallmark of PGM8. Scientists with a breadth of approaches shared their differing experience and targets around common chemical foci, and these can be exemplified by an overview of the reports of the invited speakers.

The wel-established antitumour activity of cisplatin and carboplatin, and the onset of tumour resistance to them, was discussed by Lloyd Kelland (St. George’s Hospital Medical School, London, U.K.); and here there siill remain many important targets. Phase I trials of a ruthenium(I1I) complex were reported by Gianni Sava (University of Trieste, Italy), and these show promise for a selective effect on lung metastases. Indeed, ruthenium complexes occupied a significantly important position in the biological and medicinal chemistry theme, with Jackie Barton (Caltech, U.S.A.) using them to monitor electron transfer ranges and iden- tify the effect of oxidative damage on the conductivity of DNA. Peter Sader (University of

Edinburgh, U.K) described how his work on coordination spheres interacted with DNA bases is being extended to organometallic centres.

Control and exploitation of coordination spheres was preeminent in the programme. Many examples were elegant, such as the helicate complexes of open chain tetra- and hexa-dentate phosphines (Bruce Wild, Australian National University, Canberra) and osmabenzenes and fused osma-aromatics (Warren Roper, University of Auckland, New Zealand), while others chal- lenged conventional thinking, such as the careful design of complexes with monodentate phosphines acting as bridgmg ligands (Helmut Werner, University of Wiirzburg, Germany). Probably the ‘simplest’ hgand sets were presented by Gary Schrobdgen (McMaster University, Canada) who compared the htgh oxidation states of osmium and xenon (these elements have the widest +8 oxidation state chemistry). The simplicity of the formulae belied the technical challenges of unrav- elling this chemical frontier.

For the most part, ligand sets were chosen to engender attractive physicochemical properties. These included the luminescent properties of ter- pyridyl complexes of iridium and ruthenium (Gareth Williams, University of Durham, U.K), and the non-linear optical materials based upon dendrimeric oligomers of rutheniumQI) bipyridyls (Hubert Le Bozec, Universitt de Rennes 1, France). Dendrimers and other polymeric architec- tures (rings, chains and helices) have been synthesised with impressive control by Shgetoshi Takahashi (Osaka University, Japan), and Ian Manners (University of Toronto, Canada) described his control over the synthesis of different types of ferrocenyl polymers.

Catalysis was one of the recurring reasons for ligand design, with Duncan b Bruce (Univertsity of Exeter, U.K) demonstrating that metallorganic

Phtinnm Metalr Rm, 2002,46, (4), 165-168 165

Platinum Metals in Biological and Medicinal Chemistry By Matthew D. Hall, Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW 2006, Australia

The Eighth International Conference on the Chemistry of the Platinum Group Metals provided an ideal opportunity for researchers to report their latest results on research and development in the field of biological and medicinal chemistry with respect to the platinum metals. A number of exciting new directions have emerged in this field, and these are summarised below.

Professor J. K. Barton (Caltech, U.S.A.) opened the proceedings, describing the elegant use of met- allointercalators to probe charge migration through DNA. DNA base mismatches and drug lesions (including those from cisplatin) on DNA can be characterised using this method. Her research group is currently embarlung on exciting in yitro cell studies using these novel probes.

The current status of several platinum drugs in clinical studies was reviewed by L. R. Kelland (St. George’s Hospital Medical School, London, U.K.) who described the challenge of drug resistance that needs to be faced in future drug development. While cisplatin and oxaliplatin remain successful in the clinic, novel drugs such as JM216 and BBR3464 are currently under evaluation. Professor T. G. Appleton (University of Queensland, Australia) described the complex reactions with endogenous thiols that contribute to tumour resistance, and their examination using NMR techniques.

While platinum drugs are the major research

thrust of platinum metals in medicinal chemistry, the emergence of several promising ruthenium complexes with antimetastatic and antitumour activity was described by Professors G. Sava (University of Trieste, Italy) and P. J. Sadler (University of Edinburgh, U.K.), respectively. Complexes trialled by Sava have been shown to localise in the lung basement membranes, not in DNA like many platinum drugs, thus preventing lung cancer metastasis. Sadler described the development of RuQI) arene complexes with reduced toxicity, non-cross-resistance and a different spectrum of activity to platinum compounds. Structure-activity relationships have been developed and highly selective DNA binding has been demonstrated. While it is clear that the development of further platinum chemotherapeutics is an ongoing endeavour, the emergence of active ruthenium compounds with the potential to enter clinical trials demonstrates that the medicinal chemistry of the platinum metals now has even wider potential.

The Author Matt Hall is a Ph.D. student at the Centre for Heavy Metals Research, University of Sydney, working on the biological fate of Pt(lV) antitumour complexes under the supervision of Professor Trevor W. Hambley. His interests are in bioinorganic chemistry, the biological fate of metals in medicine, and spectroscopy in cellular and biological systems.

Matt Hall is the joint winner of the Platinum Metals Review PGM8 conference student article competition.

liquid crystals could act as templates for the synthesis of heterogeneous metal catalysts based on mesoporous silicas. Jan Backvall (University of Stockholm, Sweden) demonstrated the use of allenes as nucleophiles in palladium-catalysed couplmg reactions, and the emphasis of palladium mediated C-C coupling reactions was continued by Hans de Vries (DSM Research, Geleen, The Netherlands) who presented thoughtful developments of Heck reactions. An alternative approach to C-C couplmg, namely hydroformlyation, was also stressed, with Kyoko Nozaki (University of

Tokyo, Japan) describing very effective asymmetric hydroformylation catalyst systems, and Eric Hope (University of Leicester, U.K.) showing how fluoroorganic groups can be exploited in green chemistry: to enhance the solubility of rhodium and ruthenium complexes in supercritical COZ, and also utilising fluorous phases themselves as supercritical solvents.

More detailed fundamental studies relating to homogeneous catalytic processes were a feature of the programme. The elegant and penetrating studies of Bob Bergman (University of California,

Phtinmn Metah b., 2002,46, (4) 166

U.S.A.) provided great insight into C-H bond activation processes, and Zhenyang Lin (Hong Kong University of Science and Technology) showed how theoretical studies can add to the insight in an incisive way. Sylviane Sabo-Etienne (Laboratoire de Chimie de Coordination, Toulouse, France) described the activation of boranes and silanes, demonstrating the main group elements to hydro-

gen bonds as q2-ligands. Richard Eisenberg (University of Rochester, U.S.A.) reported the power of parahydrogen-induced polarisation to track through the mechanistic pathways of Hz through a catalytic cycle, while Jon Iggo (University of Liverpool, U.K.) reported on impressive technical developments with a flow cell to allow in situ NMR under h g h pressures, without

An Equilibrium in Catalyst Optimisation and Development? By G. R. Owen, Department of Chemistry, Imperial College, South Kensington, London SW7 2AY, U.K.

A number of the presentations at the Eighth International Conference on the Chemistry of the Platinum Group Metals focused on catalysis. One of the major issues addressed was the cost involved in the design, synthesis and optimisation of new catalysts. Why spend so much money and time on the preparation of expensive ligands and complicat- ed techniques when mphenylphosphine with PdC12, under standard conditions, works well?

As the conference progressed through imagina- tive and stimulating presentations it became cleat that the search for more efficient catalytic processes requires the involvement of both academia and industry. While the optimisation of the processes can be left to the industrialist, academics should dedicate their time to design and enhancement of novel systems that might involve unprecedented chemistry.

There were a number of fascinating and inspii- ing presentations. Professor B. R James (University of British Columbia, Canada) provided an amusing advertisement for the paper industry, describing the requirements for new strategies in the hydrogenation of lignul found in wood pulp, particularly one using a RuCl~3H20 and trioctylamine catalyst. This was a call to academia for some fresh ideas.

There were also some examples of novel routes for the overall dwelopment of catalytic systems. Two interesting presentations on the use of den- drimer catalysts by the van Koten group (G. P. M. van Klink and R J. M. Klein Gebbmk, Utrecht University, The Netherlands) were given. Organic products could be separated from the reaction

mixture by recently developed nanotiltration techniques. Careful choice of catalyst, the strong chelation of the pincer llgaflds in these cases, prevented catalyst leaching.

An important puzzle was also highlighted by Professor P. S. Pregosin PTHZ, Switzerland) in his talk on the ‘meta-&&yl fleet’. This interesting contribution showed that greatly improved enan- tiomeric excesses are obtained when meta-dialkyl substituted ligands are used. The reasons for this dramatic effect were discussed and studies have shown that in Pd-phospho-oxazoline ally1 complexes, the observed Cram-influence of both the N and P donors were the same. This remarkable ‘heL /i.g fleet’ dearly needs further investigation and may have many implications for reactivity.

The conference has shown that there is a great deal of chemistry which is available for study, and in partidar platinum group metals can be used to study a wide range of reactions. Pure curiosity and application-driven research will continue to be essential for the development of exciting and novel chemistry. In both cases, real investment will be required to achiwe the challenging a i m s ahead.

The Author Gareth Owen is working towards a Ph.D. in organometallic chemistry at Imperial College, under the supervision of Dr Rambn Vilar. His thesis will concentrate on the palladium-mediated reactivity and insertion chemistry of carbon-heteroatom multiple bonds, such as isocyanides, imines and heterocumulenes. His research interests include the design of novel supramolecular ligands and their uses in the control of selectivity in catalysis.

Gareth Owen is the joint winner of the Platinum Metals Review PGM8 conference student article competition.

Pkztinum Metah Rev., 2002,46, (4) 167

the attendant problems of slow gas dissolution due to poor mixing. This direct observation of homogeneous catalysis, such as hydroformylation and carbonylation, can be achieved under representa- tive conditions.

Although many of the complexes and materials describes above were ohgomeric and polymeric, few had direct metal-metal interactions. However, these were evident in the heterogeneous catalysts described by Stan Golunski (Johnson Matthey, U.K). He emphasised the ability of metals, especially palladium, to mediate the transfer of oxide ions from an oxide surface to a catalysis substrate.

Two talks, though, demonstrated differing but fascinating properties of nanoscopic metal structures; Phil Bartlett (University of Southampton, U.K.) described how liquid crystals and solid microspheres (of polystyrene and silica) could be used as templates for the chemical and electrochemical formation on mesoporous metals. These materials provide large surface areas, like those of the nanoparticles in heterogeneous catalysts, but the area within is a concave, rather than a convex, surface and generates different types of metal surface sites. It might also be expected that the large arrays that comprise mesoporous metals may be less prone to sintering than the clusters within a hgh dispersion metal catalyst. So novel chemical applications of these materials in catalysis, electrocatalysis and sensors can be anticipated.

The other approach was that of Giinter Schmid (University of Essen, Germany). His ligand-stabilised clusters lie at the boundary of molecular complexes and colloids. The Au55 type of duster with PPhs and the predominant protecang ltgand was reported to form 2-dimensional monolayers at a water-CHzClz boundary, and I-dimensional structures with different templates. A supramolecular chemistry was established between these hgh nuclearity cluster materials. The electrical conductivity across a single cluster molecule was also measured. In the junction to the nanoelectcodes, the ligand sheath acted as an insulating layer. The metal core itself behaved as a coulomb well with properties attributable to quantum size effects, rather than being merely a segment of an extended metal array.

It is unfair to the excellent contributed papers and to the poster presenters that I have concentrated on the contributions of the invited speakers. In many ways they accentuated the perception that platinum metals chemistry is a mature, but still youthful science, with new vistas opening. Indeed, that view was expressed by Helmut Werner in his thanks to Giinter Schmid. The boundaries of platinum metals chemistry are still there to be probed in a fundamental way, aided by the great array of structural, spectroscopic, imaging and analytical techniques now available to us.

Indeed, the platinum group metals themselves are now part of the array of analytical techniques, used for example in understanding the effects of damage within DNA, and the capability for effective functioning is continually being extended. Ligand design and synthesis are developing apace, and can be used to construct clefts at single metal atoms, helicate grooves in oligomers, and complex surfaces in dendrimers and polymers. As yet we do not understand these new structures well enough to predict the applications in molecular electronics, optoelectronics and catalysis. However, we can see extended arrays of metal nanostructures that have a totally untapped potential. Perhaps even less do we understand how such complexes interact with living tissue. That they can do so to therapeutic benefit is a major impetus to research. The conference demonstrated that the range of complexes and materials that could be tested comprise a vast array of types. And, as always, development of the underlying theory of all of these interactions is essential to orient further synthetic developments.

We are grateful for the organisation provided by the Royal Society of Chemistry, and also to our sponsors: Johnson Matthey, Synetix, BP Chemicals and Nycomed Amersham. On behalf of the National and Local Organising Committees, we would like to thanks all of the attendees for a memorable scientific meeting.

The Author John Evans is a Professor of Chemistry at the University of Southampton. His main interests are in surface organometallic chemistry and heterogeneous catalysis, mechanisms of homogeneous catalysis reactions and X-ray absorption spectroscopy. Professor Evans was awarded the Royal Society of Chemistry Tilden Medal in 1994.

168 pLATINUMmETALS rEV., 2002, 46, (4)

Structural Changes and Their Ianetics in Hydrogen-Containing Palladium Systems By V. M. Avdjukhina, A. A. Katsnelson and G. P. Revkevich Department of Solid State Physics, Moscow State University, 117234 Moscow, Russia

Non-trivial structural changes and phase transformation kinetics have been found to occur in palladium-hydrogen and palladium-metal-hydrogen systems during relaxation processes as hydrogen is released. In the palladium-hydrogen system these changes take place in stages: an incubation period, a period of fast degassing, a period of stabilisation, and a post-stabilisation period. In palladium-metal-hydrogen systems the structural changes and phase transformations are non-monotonous (oscillating or stochastic). Time dependent kinetics have been observed over periods of up to tens of thousands of hours. An hypothesis based upon non-equilibrium thermodynamics and hydrogen interaction factors between matrix defects and atoms in the palladium systems is proposed to explain the phenomena.

The unique ability of palladium (Pd) to absorb large quantities of hydrogen (H) was discovered about 130 years ago by Thomas Graham (1). The solution of H in Pd has a considerable effect on the physical properties of the Pd (2,3); for example, the Pd-H alloy is diamagnetic and super- conducting, although Pd itself is strongly paramag- netic. These differences are connected with the atomic and electronic structural changes which occur when H dissolves in Pd. Only atomic structural characteristics will be considered here.

Solid solutions of H in Pd correspond to 01- phase regions if the atomic ratio of HPd, nH/npd, is less than 0.024.03, and to P-phase regions if the nH/npd ratio is greater than - 0.60. When the ratio lies between these values, a mixture of both phases is present. In both the 01- and P-phases, the Pd atoms form a f.c.c. structure, with H atoms occupying octahedral interstitial sites. The distance between Pd atoms in the P-phase is - 3 per cent greater than in the a-phase, which is why the a H

P phase transition process is accompanied by defect generation. The structural changes talung place in Pd-H during saturation with hydrogen and during degassing have become the subject of sys- tematic research. The changes occurring in the lattice and in the defect structure during the 01 + P phase transition up to P saturation, and during courses of P + degassing are of particular inter-

est. These processes and their kinetics have been examined in our research (4-12).

Stnkmg data obtained during our work show the important roles that the formation of defect structure (at saturation) and its transformation (during degassmg) play. Thus the nature of the hydrogen effects on the structural changes in Pd-H solutions and on the kinetics is significant. The mutual disorder in the distribution of Pd and other metal atoms is an additional source of defect structure formation. The most striking effects may be expected in solutions where the metal is very different to Pd - in terms of its affinity to hydrogen. Some new characteristics of the structural changes that appear when Pd systems are saturated with hydrogen can also be expected. Our results confirm that these structural changes are non-

Characteristics of the structural changes in Pd and some Pd-M alloys at saturation and during degassing will be considered here. X-ray techniques described elsewhere were used (1621).

trivial (13-21).

Samples and Methods of Investigation Samples of Pd alloys were prepared by arc melt-

ing from highly pure (99.98Yo) elements in an argon atmosphere using a titanium getter, followed by annealing (for 24 h) at 900°C at a pressure of lo* mm Hg to reach a homogenised

P/azinwm Metah h., 2002,46, (4), 169-176 169

n - 1 5

- ;; 00.

-054

I TIME, minutes

1

3

I .

Fig. I The logarithmic dependence of the Pphase concentration ( p ) in Pd on the hydrogen saturation time. The lines relate to regions or ‘blocks’ (hkl blocks) of coherent scattering with crystallographic planes. The initial incubation periods for the three blocks can be seen before the lines begin. Line 1 is for ( 1 0 0 ) blocks Line 2 is for (311) blocks Line 3 is for ( I 10) blocks

state. After homogenisation, the samples were cut (using an electric spark method) into discs, 16-18 mm in diameter and 0.2-5 mm thick. These were then ground and polished with diamond paste to a mirror-like condition. The X-ray diffraction maxima of these samples were wider than for non-deformed samples. The grinding and polishing had created a deformed surface layer to a depth of > 10 pm (greater than the X-ray penetration depth (4 to 5 pm)). Samples were hydrogenated electrolytically ( 7 4 0 minutes at a current density of 2 5 8 0 mA cm-’) in a bath of aqueous NaF solution (~?J’o) at room temperature. The sample under investigation was made into an cathode, the anode was a Pt plate. Degassing was performed in air at room temperature. In some samples annealing removed the effects of the deformation. Hydrogen saturation was attained after one sequence or after repeated cycles of ‘saturation- degassing’ (cycling).

Peculiarities of Phase Transformations in Pd-H

Plots of the dependence of the P-phase concentration p(t) in Pd on saturation times at low current density (2.5 mA cm”) show a logarithmic dependence between the In(1 - p) function and the

time, see Figure 1 (7). Lines 1, 2 and 3 relate to regions or ‘blocks’ of coherent scattering ((hh’) blocks) which have crystallographic planes with (loo), (311) and (110) indices, respectively, parallel to the external surfaces of the sample.

The experimental points lie on straight lines that do not pass through the coordinates (0,O). The dependence of the P-phase concentration on time is:

P(4 = ’ - *[- rtt- fdl

where y represents the logarithmic rate of P-phase growth and to represents the duration of the incubation period. Both y and t o depend on the crystallographic orientation of the ‘block‘ planes with respect to the external surface. The factor is a maximum for the (100) blocks and a minimum for the (110) blocks, while to is a minimum for (100) blocks and a maximum for (110) blocks. The dependence on orientation is considered to be greater for y than for to.

In addition, to and y depend upon the current density,j. A s j increases up to 25 mA cm-’, the incubation period to decreases almost 40 times for the (100) block while y increases by one order of magnitude. These findings can be explained by the kinetic theory of first-order phase transformation (7). According to this theory, the P + a phase transformation can take place when the decrease in internal energy (due to a-phase formation) is greater than the amount of energy needed to make boundaries between the new phase and the old one, to generate defects and to increase the elastic energy of the matrix. (Elastic tension will appear because of differences in the specific volumes of the phases).

During the a + p transformation, the effective pressure resulting from the saturating hydrogen, (defined by the charging current density in the electrolyte bath) becomes part of a ‘thermodynamic stimulus’. The ‘embryos’ of the new phase at the a + P transformation are in plate form. Due to the increasing number of ‘embryos’ there is an energy loss linked to the elastic tension in the ma&, this energy loss is anisotropic. The elastic energy associated with the appearance of the ‘embryo’ phases reaches a minimum when their surfaces are parallel

Pkainwm Metah Rm, 2002,46, (4) 170

to the crystallographic (100) plane. The defect structure affects both the ‘thermo-

dynamic stimulus’ and the phase transformation kinetics. Phase transformations occur by a sponta- neous movement of the boundary between the a- and P-phases (22). In fact, the rate of increase of the @phase concentration depends on the height of the energy barriers which have to be crossed during migration of the a-crystal boundary (as a - phase transforms into P-phase) (12). The defects, which lead to irregularly distributed energy barriers of different heights, hamper movement and also decrease the a + P transformation rate. The energy of the interphase boundary migration reaches a minimum when the ‘embryo’ surface is parallel to the (100) crystallographic plane.

The factors specified above explain the existence of the ‘incubation’ period and its anisotropy. The value of to decreases as j increases, while to

increases as the defect concentration increases and there is stronger anisotropy with the rate of new phase growth.

Research to understand the factors involved in the structural changes duting the p + a transformations was performed on annealed samples after a single saturation and deformation, and on annealed samples saturated with hydrogen by repeated cycling.

Annealed Samples with a Swe Saturation For a single saturation annealed sample, the

P + a phase transformation (j = 40 mA cn-*, tSat = 15 min) began immediately after hydrogen saturation. During the first 25 hours the P-phase content decreased 30 times (6). The first 5 hours was the incubation period in the deformed sample. During the next 25 hours the P-phase concentration decreased 2.5 times and during the next 150 hours the P-phase decreased by up to 30 per cent of its original value.

The changes in P-phase concentration in an annealed sample during saturation cycling are shown in Figures 2 and 3 (11). In Figure 2 the incubation period is missing for the first three cycles. The degassing rate decreases as the number of cycles increases. The incubation period appears after the fourth saturation.

-?

r i

I1 I” I

4 0 . I I

I I I

lo-

0-

I I I I

I I I I I I I

I I

0 5 10 15 I 20

TIME, days

Fig. 2 Dependence of the /%phase concentrution on time for cycles I , 11, 111 and IV The arrows show that p changes at hydrogen saturation. In IV thejlut area of the initial incubation period can be seen

100, 1

60 I a

4 0

I , . . , . , . . J

20 40 60 80 100 120 140 160 TIME, thousand hours

Fig. 3 Dependence of the /%phase concentration on time a f e r the ninth hydrogen saturation for the (100) and (311) blocks. The incubation period is omitted but the other stages of degassing: the fast decrease in p concentration, stabilisution, and post-stabilisation with oscillations in the /%phase concentration, can be seen

Figure 3 shows the dependence of the P-phase concentration, p(t), on time after nine saturations. Immediately after the ninth saturation the value of p(t) was 80 per cent; this value had been constant over a period of 4000 hours. The P-phase concentration then decreased over 46,OOO hours. After this time the P-phase concentration remained constant for 50,000 hours, and then began to change again, with oscillating behaviour. The p + a process thus appears to have a ‘stage-like’ character.

Unlike the 01 + p process, the P + a transformation occurs spontaneously in air, although the initial stage is hampered by the defect structure that is already present. Further progress is influ- enced by the generation of new defects and then

PIdimm Metah Rev., 2002,46, (4) 171

.- E A n c .- E w e P >r r

-1.2

- 1.6

- 2.0

47

0 10 20 30 40 TIME, days

0.4

0

31; -0.4

5 -0.8

-1.2

- 1.6

0 0

50 60 70 80 90 TIME, days

by transformations that follow defect generation in the defect structure. An incubation period was noticed after a single saturation only in a deformed sample, but was noted in annealed samples after the fourth saturation. After nine saturations the incubation period became much longer following mechanical treatment of the surface because by then the dislocation density had been increased.

Decreases in p(t) during the next stage of degassing show exponential characteristics only when the defect concentration is not large. Increases in defect concentration, and the resulting creation of complexes (vacancy complexes, dislocation walls) lead to the appearance of lugher and wider energy barriers in that region. Decreases in p(t) can be described by a power dependence or even by a logarithmic function dependence on t, as postulated in (12). Any kind of time dependence (power or logarithmic) relates to a transition to another kind of defect. The transition to the next stage where p(t) stops changmg rmght correspond to specific trans-

Fig. 4 The dependence .f ln(14,x/t2~w) on the relaxation time for Pd-11.3 at.% W alloy afrer the third hydrogen saturation

formations in the defect struc-

ture. One of the characteristics of the transformation is the growth of blocks in the (x-

phase, which occur because regions of the dislocation wall migrate to block boundaries (11). As this process can occur in different parts of a sample at different rates, an additional

irregularity appears in the system in the distribution of energy barriers in the a-phase crystals. This leads to additional hampering of the interphase boundaries, which stops p(t) decreasing. After the growth of the blocks is completed the 'hampering factor' of boundary migration should disappear.

The accumulation of defects and hydrogen at the boundaries of the block regions can lead to an opposing process. This causes p(t) to change (oscillating character) and thus produce the next stage of relaxation. The character of the structural changes that take place at hydrogen saturation and subsequent degassing seem to be closely related to the transformations simultaneously occurring in the defect structure.

Structural Changes in Pd-M-H Alloys and Their Time Dependence

The unusual kinetics found for the structural changes caused by transformations in the defect structure encouraged us to look at the kinetics of

Phrinwm Mekdr Rm, 2002,46, (4) 172

Fig. 5 Profiles of the X-ray diffraction maximum for Pd-8 at.% Er alloy, at 20, 130, 330 and 1300 minutes after saturation with hydrogen n Initial state of

diffraction maximum

78 79 00 81 82 28, degrees

structural change in Pd-M-H alloys. Kinetic aspects of these structural changes have been examined in Pd alloys with tungsten, W, (13-14), samarium (15), erbium, Er, (16-21), and in more detail on annealed Pd-W (11.3 at.% W) and deformed Pd-Er (8 at.% Er). The alloyhg elements are characterised by their degree of affinity to hydrogen. Tungsten has a lower affinity for hydrogen than Pd, while Er has a %her affinity. In the equilibrium diagrams for these alloys, there is no P-phase region for a Pd-W alloy containing 11.3 at.% W, in fact, the Pd-11.3 at% W alloy is characterised by regions rich in W (2-3 nm in size) (23), and by superfluous concentrations of vacancies (24). Pd-Er alloys (8 at.% Er) are also dose to the solubility boundary.

Palladium-Tungsten Alloys The dependence of the intensities, In(b/Izo~),

on time in Pd-W doys is shown in Figure 4 after the third saturation (Im and Izm are the normalised intensities of the X-ray diffraction maxima for 400 and 200, respectively) (1S14). The dependence seems to be quasi-periodic as its character shows that two types of oscillations may be occurring in the system. The first oscillation is connected to the structural changes which cause the quasi-periodic changes in the function. During the initial stage, this oscillation has a period of - 7 days. The second oscillation is connected to sa~ctural changes characterised by abrupt short-term broad-

ening of the diffraction maxima and decreases in their upper regions which occur every 4 to 5 weeks (the broadened diffraction maxima tvmgs' expand so far that correct measurement is impossible). Quasi-periodic oscillations of the first type change to stochastic oscillations after transition through a second-type structural change.

The decrease in the I n ( I ~ / I ~ ) function for the first process can be caused by the appearance of defect regions of size 2-3 nm (25) and specific volume. Increases in the In(Im/Izm) function can be associated either with solutions of these regions or with the approach of their specific volumes to that of the matrix (defect disappearance). The width of oscillation of the difftaction maxima may be connected with the appearance and subsequent disintegration of dislocation loops of size 5 1 0 nm

(25). The appearance of oscillation in the structural

change after hydrogen saturation of the system indicates that hydrogen-rich clusters have been formed in the Pd matrix. The specific volume of these dusters is larger than that of the ma& and thus the dusters are not thermodynamically stable under normal conditions. For a 'non-contradicto- if model of this phenomenon it can be supposed that stability will increase if the number of defects decreases - because superfluous vacancies diffuse into the hydrogen-enriched dusters. A lack of vacancies arising during this process in W-rich regions will be stimulated by contra-directed

Pkztinum Metals Ra., 2002, 46, (4) 173

(i400/i200)

45 46 47 45 46 47

2e, degrees

Fig. 6 Profiles of X-ray diffraction muxima for Pd-8 at.% Er alloy at various times after hydrogen saturation: ( I ) 1.5 hours, (2) 7 hours. (3) 25 hours, ( 4 ) 48 hours, (51 I20 hours, (6) 4200 hours

vacancy diffusion; this will result in oscillation of the moving vacancies and will lead to first-type structural oscillation. After a few cycles, the vacancy concentration in the Pd-rich regions becomes so large that it would seem more advantageous to form large vacancy dislocation loops during the intermediate period (although these loops would be unstable). The loops disintegrate soon after they form, and then the process of defect cluster formation and disappearance begins again. This

model is, of course, an hypothesis and requires more direct proof. Nevertheless, it does describe the experimental data and may be used as the basis for a stricter model of the observed phenomena.

Palladium-Erbium AUoy The initial state in deformed Pd-8 at.% Er alloy

(caused by grinding and polishing) is characterised by an essentially non-homogeneous distribution of the constituents and by a strong stretching tension (acting outwards to the surface) that acts perpen- dicularly to the surface. After hydrogen saturation the tension changes to compression. Maximum compression was reached two days after hydrogen saturation. After eight days the value of the compression had decreased by 25 per cent; then it remained practically constant for the next 1.5 years

After hydrogen saturation the profile of the X- ray diffraction maxima becomes doublets, see Figure 5. This indicates that two phases develop that essentially differ from each other by the period of the lattice. The time dependence of the maximum profile has oscillating character, see Figure 6. Computer analysis of the profiles allowed us to determine the time dependencies of differences in Er concentrations in corresponding phases and specific parts of these phases. The data in Figure 7 indicate that irregular oscillations (stochastic) in the indicated characteristics have been occurring for 1.5 years. The oscillations occur in the initial stage of degassing when there is 10-20 per cent of H in the system and also in the later stages when the concentration of H is not more than 1 per cent (1S20). The data are explained

(17-18).

04 I 1.5 10 1 0 0 1000 10000

TIME, hours

Fig 7 The dependence cfthe concentration of specific parts of corresponding Er-rich phases in Pd-8 at.% Er alloy on time, after hydrogen saturation

Pkafinnm Metah Rm, 2002,46, (4) 174

with a model which takes into account the microscopic theory of alloys and a synergy model.

The lattice compression found in the alloy afier hydrogen saturation can be caused by transformation of the defect-metal (DM) complexes present in the alloy before saturation into hydrogen- defect-metal (HDM) complexes because the hydrogen-defect bond in Pd has hgher energy (26). Thus, the HDM complexes have low specific volume. As Er has a hgh affinity to hydrogen, these complexes attract Er atoms and trap them. They play a dual role, keeping the system in a non- equilibrium state and allowing the appearance of ascendmg diffusion. According to synergy consid- erations, non-equilibrium conditions in the system permit oscillations connected to self-organisation of the defect-structural states to appear (27). A competition between ascendmg diffusion and gra- dient diffusion provides a mechanism which allows any possible oscillations to be realised.

The various diffusion fluxes caused by the competition in the two-phase system with the Er traps can cause oscillations in the phase transformation kinetics. The stochastic nature of these oscillations may be related to differences in relaxation times of the different oscillation processes.

Conclusions Structural changes peculiar to the hydrogen-

containing systems Pd-H and Pd-M-H, where M is a metal having a different affinity for hydrogen to Pd, have been considered. Non-trivial kinetics for the p -+ CL transformation in Pd-H have been found. The most important feature is the altemat- ing stages in the P-phase concentration which may or may not occur. This phenomenon is related to the influence of the origmal defect structure on the transformation kinetics during the p + CL phase transformation. The second important feature in the CL H p transformation is the strong dependence of the associated p(t) function on the orientation of the (hM) blocks relative to the external surface. This is caused by the elastic energy dependence resulting from the orientation of the plate formations.

In Pd-M-H systems the kinetics of the structural changes have oscillating character related to the

defect subsystems caused by the non-homogeneous distributions of the metal and the associated non-homogeneous hydrogen distribution. Hydrogen is captured by regions that have a hgh bondmg energy for hydrogen and this keeps the system in a non-equilibrium state. This can lead to several diffusion fluxes where ascendmg and gra- dient diffusions compete.

Such ‘static’ instability can transform the dynamics to dynamics similar to those of Benard cells (27). Accordmg to alloy structure considera- tions, the oscillating character of the structural changes can have different characteristics, indud- ing an alternating appearance and, in Pd-W-H, the disappearance of the defect regions. In Pd-Er-H the structural changes may also have the form of stochastic phase transformations.

The long-term oscillating structural changes in hydrogen-containing alloys correlate with changes in strength characteristics, for example, those in rolled steel (28). Further investigations of the observed phenomenon will be to find Pd alloys in which it occurs and to examine its nature and any practical applications. Alloys Pd-Mo-H and Pd- Ta-H alloys are now being studied.

Acknowledgement This work has been supported by the Russian Fund of

Fundamental Research, under grants Nos. 99-02-16135 and 02- 02-16537.

References T. Graham, Phil. Trans. Rcy. Soc., 1866,156,399 P. V. Gel’d, R A. Rjabov and L. P. Mokhracheva, “Hydrogen and Physical Properties of Metals and Alloys: Transition Metal Hydrides”, Nauka, Moscow, 1985 “Hydrogen in Metals I”, eds. G. Alefeld and J. Volkl, Springer-Verlag, Berlq 1978 A. A. Katsnelson, G. P. Revkevich, S. V. Sveshnikov et a l , Metakj$aa, 1985,7, (2), 66 G. P. Revkwich, S. V. Sveshnikov and A. A. Katsnelson, I?. W Z o v , Fiz, 1988,31, (5), 102 G. P. Revkevich, A. I. Olemskoi, A. A. Katsnelson and V. M. Khristov, Met&j$a, 1990,12, (3), 71 G. P. Revkevich, A. I. Olemskoi, A. A. Katsnelson and M. A. Knjazeva, M O J ~ W Univ. Ply . BnL, 1992,

G. P. Revkwich, A. I.’ Olemskoi, A A. Katsnelson and M. A. Knjazeva, P ~ J . Met. Met., 1993,76, (l), 101 A. A. Katsnelson, M. A. Knjazeva, A. I. Olemskoi and G. P. Revkevich, S n ~ Invest., 1998,13,1443

33, (2), 74

P/acinrcm Metah Rev., 2002,46, (4) 175

12

3

4

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6

7

8

9

10

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17

18

19

20

21

A. A. Katsnelson, M. A. Knjazeva, A. I. Olemskoi and G. P. Revkevich, Plys. Solid Stute, 1997,39, 0, 1275 A. A. Katsnelson, M. A. Knjazeva, A. I. Olemskoi and G. P. Rwkevich, Mosmw Uniu. Plys. BwU, 1997, 38, (6),46 A. A. Katsnelson, M. A. Knjazeva and A. I. Olemskoi, Ply . Solid Stute, 1999,41, (9), 1621 A. A. Katsnelson, A. I. Olemskoi, G. P. Revkevich and I. V. Suhorukova, Mosmw Uniu. Ply . Bwll., 1994, 35, (3). 68 A. A. Katsnelson, A. I. Olemskoi, G. P. Revkevich and I. V. Suhorukova, Ply&-U@kbi, 1995,165, (3), 331 A. A. Katsnelson, G. P. Revkevich and V. M. Avdjukhina, Mosmw Uniu. Ply. BwU., 1997,38, (3), 68 V. M. Avdjukhina, A. A. Katsnelson and G. P. Revkevich, Sw$ Invest., 1999,14, (2), 30 V. M. Avdjukhina, A. A. Katsnelson, N. A. Prokofjev and G. P. Revkevich, Mosmw Uniu. Phys. BwU, 1998,39, (2), 71 V. M. Avdjukhina, A. A. Katsnelson and G. P. Revkevich, Ctyst. Rtp., 1999,44, (l), 49 V. M. Avdjukhina, A. A. Katsnelson and G. P. Revkevich, Momw Uniu. Pbs. BwU, 1999, 40, (5), 44 V. M. Avdjukhina, L. Dabrowskii, A. A. Katsnelson, J. Suvalskii, G. P. Revkevich and V. M. Khristov, P l y . SolidState, 1999,41, (9), 1532 V. M. Avdjukhina, A. A. Katsnelson, D. A. Olemskoi, A. I. Olemskoi and G. P. Revkevich, P l y . Met. Met., 1999, 88, (6), 576

22 H. C. Jamieson, G. C. Weatherly and F. D. Manchester,J. LwCommon. Met., 1976, 50, (l), 85

23 S. A. Alimov and A. A. Katsnelson, Ply . Met. Met., 1966,22,468

24 A. A. Katsnelson and A. I. Olemskoi, “Microscopic Theory of Non-homogeneous Structures”, Mir Publishers, Moscow, AIP, New Y o 4 1990

25 M. A. Krivoglaz, “Diffraction of X-Rays and Neutrons by Non-Ideal Crystals”, Naukova Dumka, Kiev, 1983

26 S. M. Myers, M. J. Baskes, H. K. Birnbaum et ul, Rev. Mod Pkys., 1992, 64, (2), 559

27 I. Pngogjne, “From Being to Becoming Time and Complexity in the Physical Sciences”, W. H. Freeman and Co., San Francisco, 1980

28 V. M. Piskovets, T. K. Sergeeva, Yu. A. Bashnin and 0. V. Nosochenko, SteeI, 1994,(7), 60

The Authors Valentina M. Avdjukhina is an Associate Professor of Physics at Moscow State University. Her interests include X-ray diffraction crystallography, non-equilibrium systems, metal-hydrogen alloys and platinum metals. Albert A. Katsnelson is a Professor of Physics at Moscow State University. His interests include X-ray diffraction crystallography, non-equilibrium systems, metal-hydrogen alloys, the electronic theory of condensed matter, synergetics and platinum metals.

Galina P. Revkevich is a Senior Scientist at Moscow State University. Her interests are X-ray diffraction crystallography, non- equilibrium systems, metal-hydrogen alloys and platinum metals.

Polymer-Supported Rhodium Catalysts Soluble in SC-CO? In organic syntheses utilising homogeneous cat-

alysts, the catalysts are dissolved in a suitable solvent which also acts as the reaction medium. These solvents are often toxic organic liquids, so there is a growing need to replace them with envi- ronmentally benign solvents, such as water or supercritical carbon dioxide (sc-COZ). At present, the majority of organic syntheses are solvent-sensi- tive and most homogeneous catalysts are not soluble in either water or SC-CO~.

Separating and recovering the homogeneous catalysts at the end of the reaction is also a major problem. To overcome this, increasing attention is being directed at developing polymer-supported ligands for complexing with homogeneous metal catalysts for straightforward membrane separation.

Researchers at Texas A & M University, U.S.A.,

The polymer was prepared by polymerisation of the monomer lH,lH,2H,2H-heptadecafluorode- cyl acrylate (zonyl TAN) and N-acrylosuccinimide (NASI); zonyl TAN increases the solubility in sc- COZ while NASI provides attachment sites for the catalyst. N H ~ ( C H ~ ) ~ P P ~ Z (DPPA) was then used to exchange the NASI groups in the polymer. Finally, this was reacted with pulCl(COD)]z to obtain the sc-COZ soluble, polymer-supported Rh catalyst. As the polymer is a very large molecule it was easily separated by a membrane.

Catalyst hydrogenation activity was evaluated using 1 -0ctene and cyclohexene at different molar ratios of substrate:% and different temperatures. Most reactions were performed at 173.4 bar pressure for 12 hours. Conversion of I-octene to n-octane was nearly 100%. Conversion of cyclo-

have now succeeded in developing a homogeneous catalyst that is soluble in sc-COZ solvent (2. K. Lopez-Castillo, R Flores, I. Kani, J. P. Fackler and A. Akgerman, Ind Eng. Gem. Res., 2002, 41, (13), 3075-3080). They did this by attaching a homogeneous rhodium (Rh) catalyst to the backbone of a fluoroacrylate copolymer. catalyst is reproducible.

hexene increased 4th temperature: at 368 and 393 K, the maximum conversions were 39 and 51%, respectively. For this hydrogenation, the catalyst was Rh(TAN15DPPA)Cl with a Rh dimer:polymer ratio of 1:3 and a Rh content of 1.95 mg of Rh/g of catalyst. The synthesis route for this Rh-polymer

Plafnwm Metah Rev., 2002,46, (4) 176

9th International Platinum Symposium AN EXCHANGE OF INFORMATION AND IDEAS ON GEOLOGICAL AREAS OF PLATINUM GROUP ELEMENTS MINERALISATION

By R. G. Cawthorn Department of Geosciences, University of the Witwatersrand, PO Wits, 2050, South Africa

The geological community has been hosting International Platinum Symposia since 1971, the first being held in Melbourne, Australia. Since then Denver, U.S.A.; Pretoria, South Africa; Toronto, Canada; Espoo, Finland; Perth, Australia; Moscow, Russia; and Rustenburg, South Africa, have hosted the event at intervals of approximate- ly four years. Over the years the number of delegates has increased by a factor of four (in exact proportion to the quantity of platinum group elements (PGEs) mined and the price of platinum), with over 200 people attending the latest, the 9th International Platinum Symposium, held in Bdhngs, Montana, U.S.A., in July 2002. The venue was conveniently placed for excursions to the Stillwater Complex, a classic layered intrusion hosting major palladium reserves, exposed in the Beartooth Mountains in Montana.

The delegates to these symposia come from academic, exploration, mining and government organisations, probably in that relative order in terms of numbers. At this meeang most areas of the world were represented, with the exception of Australia, which was rather surprising because considerable exploration for PGEs is underway there. These meetings are primarily intended for the exchange of geological information and ideas, with less emphasis on mining, metallurgy, and extraction. Presentations generally range from docu- mentation of exploration target areas, through the identification of assemblages of platinum group minerals in different deposits, and geochemical information and techniques, to ideas on the gene- sis of such mineralisation and identification of concepts aidmg future exploration programmes.

Areas in which PGE mineralisation were documented included the U.S.A., Canada, Brazil, India, U.K., Finland, Russia, China, Zimbabwe and South Affica, but many of these were only of aca-

demic interest, since at this stage they host no significant grades above 1-2 g t-'. However, they illustrate the type of host rocks in which mineralisation may occur, and the processes by which mineralisation was concentrated. There are several rock associations that host PGE occurrences: layered intrusions, concentric intrusions, brecciat- ed rocks related to intrusions, ophiolite complexes, komatiites, meteorite impacts, and alluvial deposits.

Not mentioned at this meeting were the large tonnages, but very low-grade, occurrences found in mud rocks formed under oxygen-free conditions at the bottom of inland seas. However, in these the grades are extremely low and it is unlikely that they will be exploited. These different settings and processes are briefly summarised.

Intrusions Layered intrusions form from the slow coollng

of large volumes of lava or (more precisely from its underground equivalent) magma. Layers of crystals

of different compositions (mainly of non-economic minerals) are deposited by this process, and extensive thin, parallel layers form that can be easily traced laterally. Examples, are the Bushveld (South Africa), Stillwater (Montana) and Great Dyke (Zimbabwe) intrusions, that may have one or two highly PGE mineralised layers. In other cases the underground magma did not form parallel layers of rocks, but produced a pipe-like body w e a volcanic feeder pipe), and each eruption produced a discrete concentric cylinder of rock. Several such PGE-bearing intrusions occur in the Urals in Russia.

There is another potential zone of mineralisation in layered intrusions. The heat from such magmas causes melting of the underlying rocks and reaction between the magma and the rocks in

Pl;lfnwn Met& Rm, 2002,46, (4), 177-1 80 177

the floor can cause mineralisation, especially of nickel and copper, but PGEs may be a byproduct. This mechanism has produced the major palladium reserves at Noril’sk in Russia.

Igneous intrusions are always associated with much heated groundwater (as seen in natural geysers). The steam can react with low-grade mineralised intrusions and concentrate the PGEs into hydrothermal (literally hot water) deposits. The steam and later intrusions permeate through, and break up the original rocks into fragments (called breccias), and in that way can leach the PGEs from the original rocks to deposit them in high-grade areas. The Lac des Iles palladium-rich body in Canada is such an example.

Ophiolite Complexes Lavas originate from deep inside the earth, in a

part called the mantle, which lies at least 35 km below the surface of the earth. Low concentrations of PGEs occur in such mantle rocks. Usually these rocks never reach the surface. However, where continents are crushed together in mountain-build- ing events (such as the Himalayas, Alps, Rockies and Urals) slices of mantle rock can be thrust up to

the surface. These rocks are called ophiolites and are distinctive compared to surrounding rocks. They have been extensively explored since very minor concentrations of PGEs are found in them.

One of the characteristic rocks containing PGEs in an ophiolite is chromite, and while these bodies have been extensively investigated worldwide, none has yet proved economic. The continued interest in them possibly arises from the fact that the smgle largest resource of PGEs in the world is a layer of chromite in the Bushveld Complex (l), called the Upper Group 2 (UG-2) chi-omitite layer.

Komatiites A relatively minor occurrence of PGEs lies at

the base of lava flows, especially extremely ancient lavas known as komatiites. In these settings, molten lava has eroded a channel down the flanks of the volcano, and precipitated nickel-copper sul- fides in which the PGEs are a minor commodity. Although these bodies can contain high grades of

nickel, the tonnages and grades of PGEs, as mined in Canada and Western Australia, are relatively small.

Meteorite Impacts Early in earth’s history, numerous meteorites

impacted the earth, and caused massive melting of the rocks on the surface. One such example, at Sudbury, Canada, produced a huge bowl-shaped mass of molten rock in an area where considerable copper, nickel and PGE mineralisation was already present. This mineralisation became concentrated in the molten rock and eventually produced the major deposits at the bottom of the bowl now being exploited at Sudbury.

Alluvial Deposits Weathering of PGE-bearing rocks can produce

secondary enrichment in the overlying soils or river systems. The PGEs are extremely dense minerals and also inert (not altered by surface processes). Hence, they become concentrated in soils and rivers, while all the other minerals are decomposed or washed away because of their lower densities. In this way a low-grade occurrence of PGE mineralisation may be upgraded in river systems. (Gold is also concentrated by this same process.) Such deposits are called alluvial deposits. The first platinum ever found, in South America, was concentrated by this process, but no high- grade source rock has ever been found there. In Russia considerable mining and exploration is being undertaken for such occurrences. Since they lie at the earth’s surface it is unlikely that enormous deposits have escaped detection by the prospec-

The statement that the PGEs are inert is not absolutely correct. Under certain conditions extremely small concentrations can be dissolved in very corrosive heated groundwater systems. These concentrations can then be deposited when the water cools or is neutralised by mixing with fresh water. Clay minerals may adsorb the precipitating PGEs, and in ancient black mud-rocks in Europe extremely low concentrations (totally uneconomic) of PGEs have been reported. Q h s is the old Kupferschiefer, mined in

tors’ pans.

Plarinutn Met& Rm, 2002,46, (4) 178

central Europe for copper in the Middle Ages.) Examples of all these rock types were docu-

mented at the 9th Internetional Platinum Symposium, and several examples from different parts of the world were reported on for the first time. In other cases, exploration programmes and academic studies on the origin and extent of known mineralisation were documented. There are still many challenging aspects as to how economic deposits of PGEs become concentrated, and exploration programmes are obviously influ- enced by such hypotheses, since each hypothesis makes certain predictions about what kinds of rocks, and especially their detailed chemical compositions, are the best pathfinders or fingerprints for mineralisation. For example, the PGE deposits in the Merensky Reef and the UG-2 chromitite in the Bushveld Complex, the J-M Reef in Stillwater and the Great Dyke, all occur in the middle of very large layered intrusions. One school of thought is that the mineralisation ra ins downward from the overlying magma and accumulates into a layer of crystals, like the well-known placer theory for gold mineralisation. An alternative view is that hot water systems dissolve the PGEs present in very minor concentrations from low down in the intrusion and precipitate the mineralisation in these reefs as the heated water percolates upward (like blotting paper suckmg spilt wine from a table- cloth). Exploration strategies would then differ, depending upon which process was considered applicable in a certain area.

New Areas of Exploration Activity By this stage readers are doubtless askrig

whether there are any new areas of exploration activity that might lead to future economic deposits. The answer is that there is probably nothing very new. The exploration in Finland that has been ongoing for twenty years has indicated multimillion ton resources in a few different intrusions and s e w , and regional exploration is probably evolving more to feasibility studies and financial evaluation. Establishing continuity of grades and extraction processes is now occupying centre stage.

Lagging somewhat behind the Finnish progress

is the exploration of the enormous intrusion in Duluth, Minnesota. This intrusion has been shown to have very large quantities of mineralisation, mainly of copper and nickel with minor PGEs, fairly near to the floor contact However, this mineralisation is diffuse and variable in grade. Tonnages could be enormous, but grades are generally elusively low. Identification of specific open-pit or underground mining targets is still awaited.

In Ontario and Minnesota, there are a number of small intrusions, which have tantalising concentrations of PGEs. The general impression seems to be that broad zones (more than 10 m wide) of mineralisation at 1.5 to 2 g f’ might be amenable to open-pit operations, but that thin (less than 2 m wide), lqh-grade (Merensky Reef-style) mineralisation, accessible only by underground mining is not likely to be identified there.

There was no mention at this meeting of some other exploration regions. The Muskox intrusion in the Canadian Arctic may have Duluth-style or Platreef-style (Bushveld) mineralisation (depending upon how bullish you want to be). In Australia, there are also a number of layered intrusions in which PGE mineralisation is known and currently being examined.

Extraction Challenges Exploration for PGEs has an inordinately long

lead time. One of the reasons is that the relative proportions of the different PGEs can be very variable, and an extremely wide range of platinum group minerals might be present Given their exceptionally low abundance, determining the proportion of these minerals, and especially their intergrowth with various gangue minerals is challenging but fundamental to successful extraction.

It is this extremely complex relationship between the different platinum group minerals and the wide variety of gangue minerals that is causing the apparent extraction problems encoun- tered by the Stillwater mines. The greater age of the Stillwater intrusion and the subsequent events that have faulted and altered the rocks and their mineralogy, compared to the Bushveld Complex, have caused mining and extraction problems. To

Platinum Met& Rm., 2002,46, (4) 179

the great relief of South African Bushveld mining companies, no other area or example better typifies the statement that ‘grade isn’t everythmg’.

It is for these reasons that many papers presented at the conference focused on documen- tation of the platinum group mineralogy in a great many different settings. Dealulg with grains, typically about 0.001 cm across, and present at grades of 2 g t-’, is an extremely challenging occupation. Academic studies presented on such minerals provide information on how the PGEs could be initially concentrated in the rocks, and by contrast, their counterparts in exploration are intent on get- ting them back out again!

A Global Inventory The section above indicates that there are

unlikely to be any changes in worldwide PGE production in the short term. In an address at the meeting, the Director of the U.S. Geological Survey, Dr Charles G. Groat, had two themes. His first observation was aimed largely at those people who suggest that oil deposits are running out. He pointed out that commodiues were not necessarily running out, it was simply that a global inventory was not available, but that with a global vlllage mentality there would always be suppliers. Second, and arising from this view, was the decision that the U.S. Geological Survey would be conducting a a cooperative international global programme to assess the undiscovered nonfuel mineral resources, and that platinum would be among the fist group of commodities to be assessed. This plan is ambi- tious, and a comprehensive evaluation is expected to take seven to ten years.

This writer feels that the fist conclusion should be applied with some caution to the platinum market. There is no other commodity in the world that remotely matches the PGEs for their uneven worldwide distribution. However quickly new tai- gets are identified and brought to fruition, their contribution will be minor compared to the Bushveld Complex (2) and Noril‘sk areas. No other commodity is so dominated by so few suppliers. Given the reserve and resource figures currently available, the Bushveld (mainly platinum) and Noril’sk (mainly palladium) areas will continue

to supply 80 to 90 per cent of the world’s platinum and palladium for the foreseeable future.

The 10th symposium in this series is expected to take place in Finland in 2006. It will then be interesting to see how far towards viable commercial operation some of the sources mentioned at the 9th symposium will have come. The conference website is www.platinumsymposiu.org.

References 1

2

R P. Schouwstra, E. D. Kinloch and C. A. Lee, Phtimm Metals Rey., 2000, 44, (l), 33 R G. Cawthorn, S.A@. J. Sci., 1999,95, (11/12),481

Addendum Geologically inclined readers may wish to obtain a recent sum- mary of PGE deposits worldwide, “The Geology, Geochemistry, Mineralogy and Mineral Beneficiadon of Platinum-Group Elements”, edited by L. J. Cab4 (Special Volume 54), Canadian Institute of Mining, Metallurgy and Petroleum, Montreal, 2002; website: www.cim.org.

The Author Grant Cawthorn is the Platinum Industry’s Professor of Igneous Petrology at the University of the Witwatersrand. South Africa (E-mail: [email protected]). His main interests are researching the origin of layered intrusions and their varied mineral deposits.

Recyclable Ruthenium-BINAP Catalysts Ryoji Noyori has been involved in asymmetric

homogeneous hydrogenation for over t h t y years. His work in this important area has resulted in catalysts with hlgh selectivity and wide application (T. J. Colacot, Pkdnum Metalr Rey., 2002,46, (2), 82-83). Among catalysts he has helped to develop is Ru- BINAP, (BINAP = 2,2‘-bis(dipheny1phosphino)- 1,l’-binaphthyl) which, as Ru(lI)-BINAP dihalide complexes, provides a versatile general asymmetric hydrogenation of functionalised ketones.

Now, scientists from China have synthesised dendridc Ru-BINAP catalysts that are peripherally alky-functionalised (G.-J. Deng, Q.-H. Fan, X.-M. Chen, D.-S. Liu and A. S. C. Chan, Chem. Commun., 2002, (15), 1570-1571). These catalysts can be used for asymmetric hydrogenation in an ethanol/hexane reaction medium. Acids: 2-arylacrylic, 2-phenyl- acrylic and 2-[p(2-methylpropyl)phenyl]aciylic used for model reactions had high catalytic activity and enandoselectivity. Phase separation was induced by adding a small amount of water. The hexane catalyst-containing layer can be removed for reuse.

Phtinum Mefah Rev., 2002,46, (4) 180

TM ACT Power CoatingsTM MULTIFUNCTIONAL INDUSTRIAL PLATINUM COATINGS FOR THE GLASS INDUSTRY

By Paul Williams Johnson Matthey Noble Metals, Orchard Road, Royston. Hertfordshire SG8 5HE. U.K

Almost every glass article in existence has been formed by cooling from a molten state (with the exception of the relatively tiny amount produced via sol-gel processing and similar routes). Molten glass is a difficult and challenging material to han- dle due to the extremely high temperatures required to melt and combine the glass constituents (typically 1400 to 1600°C) and to the hghly corrosive nature of glass in this state. Further difficulties arise when glass is formed using automated production equipment. Over the last century or so these difficulties have been overcome and mass- produced bottles, windows, tableware and display screens, amongst many other items, are now taken for granted. However, the various pieces of equipment used to melt, distribute and form these glass articles all suffer from continual corrosion. The corrosion causes two major problems:

First, corrosion has an obvious limiting effect on the lifetimes of the furnace and handling equipment used to melt and process the glass. For instance, some of the furnaces that produce the more aggressive glasses (such as fluoride opal glass for white tableware, or borosilicate glass for Pyrex@ articles and LCD screens) need to be completely rebuilt every two years and this can cost tens of millions of pounds each time.

Second, the products of the corrosion process (undissolved ceramic particles (‘stone’), chemical inhomogeneities (‘cord’) or bubbles (‘blister’)) can cause defects in the glass which reduce its overall quality. While the occasional defect in a beer bottle may be of minor consequence, a single minute defect in a hgh-quality lead crystal item or LCD screen panel is completely unacceptable.

Materials for Glass Making Platinum is one of the few materials that is rel-

atively immune from the corrosive effects of molten glass. Its hgh melting point (1769°C) (1)

and oxidation resistance at elevated temperatures make it the ideal material for handlulg molten glass. Ideally, the entire glass-contact surface of a glass furnace should be fabricated from platinum. However, the hgh intrinsic value of platinum pre- cludes this as an option for the majority of glass producers. Therefore, this approach is confined to the hghest-value and extremely-specialist production operations - that is, glass for flat panel display screens or glass for lenses of extremely high-power astronomical telescopes.

Instead, most sectors of the glass industry use platinum only for certain critically important items in the furnace. These items, protected by or manufactured from platinum, are subject to the most corrosion or have the greatest effect on the quality of the final product. In general, the extent to which platinum is used in a furnace is determjned by a number of factors. These include the value of the product glass, the quality required of it and the cor- rosiveness of the molten glass. For example, a single LCD glass production line uses about 350 kg of platinum in the re-, distribution and forming sections and typically lasts only 2 to 3 years. In this application, the use of platinum components is vital to the final product quality, and the high value of the product justifies the investment. By contrast, the beer bottle plant mentioned earlier may require only a few hundred grams of platinum for the thermocouples used to control the glass melt temperature. The bottle production process would certainly benefit from the use of platinum but it is not a necessity for the final product and the hlgh- volume, low-margin nature of the business makes using large amounts of platinum difficult to justify.

Platinum Fabrications Traditionally, the platinum used in the glass

industry is either fabricated to produce solid, free- standing components or is wrapped (dad) around

P L d h m Metals Rev., 2002,46, (4), 181-187 181

ceramic or high melting-point metallic components. Both methods use rolled sheets of platinum alloy (for example, 10%Rh/Pt or 20%Rh/Pt, measured in wt.%o), which are cut, formed and welded to the requisite shape. Extremely complex and sophisticated fabrications can be achieved using these processes.

However, with such a precious resource, optimisation of its use is essential and in order to minimise the amount of platinum the thicknesses of the platinum fabrications should be as small as possible. There is, however, a minimum thickness

below which the sheet is not sufficiently strong to support itself and contribute its protective and/or containment function.

Platinum Coatings An alternative technique, which utilises the ben-

eficial properties of platinum in a far more efficient manner, is by thermal spraying a protective platinum layer directly onto the glass-contacting surfaces of the production equipment. This process, known as advanced coating technology, ACTTM (2), has the capability to render the

ACT^" Platinum Coatings A C P platinum coatings are applied by a thermal spray deposition process. Platinum in wire or

powder form is fed into an oxygen-propylene or plasma flame. The residence time within the heat source is carefully controlled to ensure that the platinum is melted without vaporising it. A com- pressed gas stream fires the molten droplets onto the surface to be coated. The droplets ‘splat’ on impact and solidify almost instantly. The large differential in thermal mass between the molten particles and the substrate means that the component normally experiences ody a slight increase in temperature during the deposition process. A continuous feed of wire or powder ensures a uniform, even stream of thousands of droplets per second. Successive ‘splats’ build up to form the coating.

The thermal spray gun is controlled by a sophisticated multi-axis robot. The precise control of speed and motion obtainable ensures that even, reproducible coatings can be achieved. Coatings are applied in a purpose built coating booth which collects any ‘over-spray’ platinum, thus minimising loss of metal.

Correct preparation of the substrate material is vital to the integrity of the bond between substrate and coating. Great care is taken to ensure that the ceramic surface is in optimum condition to allow maximum adhesion of the coating. The substrate preparation methods allow the ceramic surface to be imperfect: minor defects can be rectified, but the number should be kept to a minimum.

The ACT‘M platinum deposition process is being used here to apply a thin layer of platinum to a fusion-cast ceramic block which will cover glass deliven, channels. Tlierniul spray techniques and sophisticnted robotic systems ensure that the distribution of the platinum coating matches the corefully designated coating profile: .for instance, two thicker (darker) bands of platinum can be wen on the upper surjiice

Phtitznm Mekrls Rm, 2002,46, (4) 182

The feeder chamber within u gltrs., production unit. The chamber comprise^ u 'T'-shaped cerumic tube through which the high temperuture molten glass flows from the melting urea to the forming machines. In this chumber a rotating and reciprocating screw-plunger moves stirring the glass und forcing it into the moulds. The feeder chamber is the part of the system that most requires protectioii from the corrosive eflect5 of the molten glass

coated component virtuaUy immune to the corrosive effects of the molten glass. The process is analogous to the cladding technique, where a base metal or ceramic component is protected by a platinum alloy sheet; however, the platinum is now strongly and intimately bonded to the substrate material. Rather than being a 'brick wrapped in metal foil', the component has become a composite structure. The platinum coating provides the corrosion resistance at the surface, while the substrate material provides the bulk properties, mechanical strength and shape. As the substrate now gives the system its strength, the platinum thickness can be reduced to the minimum required to ensure an impervious barrier layer and hence impart the necessary corrosion resistance. The thickness of the coating is typically in the range of 200 to 300 pm, compared to a dad% thickness of - 1 mm and above.

The obvious advantage offered by such coatings is that far less platinum can be used than in the traditional fabrication or clad- techniques. This reduction in platinum requirement also makes it feasible to use platinum in positions and applications that would not normally justify the investment of a fully dad platinum system.

Lead Crystal The effectiveness of the ACTm coatings can

be illustrated by their use in premium-quality lead crystal production. High-quality lead crystal is a

sector of the glass industry that has traditionally used significant amounts of platinum in the production process. Over the last six years, the glass industry has progressively adopted ACTm coatings as the standard production route. The best examples of lead crystal tableware have always been produced to stringent quality standards. Recently, the growing trend for uncut or hghtly cut crystal has raised these standards even hgher. Defects in the crystal are more apparent when there are fewer cuts made, so the defect tolerance is much lower. In order to meet these high-quality requirements, crystal manufacturers are increasing the number of platinum or platinum-protected parts in the production line, especially in the delivery systems close to the forming zone.

Delivery Systems The system that delivers the molten glass/crys-

tal from the melting area to the forming machines is referred to as the feeder chamber. It normally comprises a ceramic ''I" shaped tube, the vertical section of which contains a rotating and reciprocating screw-plunger. This serves the dual function of homogenising the glass (stirring action) and forcing the correct amount from the chamber into the moulds (plunging action). For high-quality crystal production, the feeder chambers are either lined with platinum alloy dad- or are ACTm platinum-coated on the internal surfaces. The quantity of precious metal required to do this is

PIninum Metah h., 2002, 46, (4) 183

ING

INGS

Material

Pt 1 O%Rh/Pt 20% Rh/Pt

I I I I

Melting point, 'C Density, g ~ r n - ~ Ultimate tensile strength (3) (fully annealed sheet), kg rnm-'

1769 21.45 13 1850 20.00 34 1900 18.72 49

obviously dependent on the size of the chamber. Typically, about 6 to 7 kg of platinum-rhodium alloy is used for the clad option and 2.5 to 3 kg of platinum for the coated version.

Pure platinum is rarely used for daddings or fabrications as it lacks the necessary strength when in the unalloyed condition. Therefore alloying additions are made to increase its strength. A common alloying addition for this purpose is rhodium, normally at 10 or 20 per cent. Rhodium is normally considerably more expensive than platinum and

Platinum Power CoatingsTM in a feeder chamber at Cwstulex (a tableware manufucturer in the C x c h Republic) thot i A pmducing a stream of molten glass. The Jervo-controlled cutting 5hear.s are on either side of the gluss stream. In full-scale operution, the chumher maintains u steady glass del ivey temperature k 0.5"C

has recently cost more than twice as much (4). This has a significant effect on the cost of a platinum- rhodium alloy relative to pure platinum. However, because ACTm coaangs utilise the ceramic substrate to provide the mechanical strength of the system, pure platinum can be used as the coating material.

If platinum protection of some form is not used, the molten glass will attack, corrode and dissolve the ceramic of the chamber, thus limiting its life. The products of the corrosion process (stone, cord and/or blister) are swept into the forming moulds and manifest themselves as clearly visible defects in the hnal product. Consequently, hgh-quality lead crystal producers regard platinum as a vital part of their production process and other producers are increasingly using it too.

Heating Options The temperature of the glass/crystal as it is

delivered to the forming moulds is a critical parameter in the production process. The glass temperature must be carefully controlled to ensure optimum viscosity and the correct coolmg/solidi- fication rate. The last stage in the production process at which the temperature can be controlled is when the glass is in the feeder chamber. The temperature is then typically around 1000 to 120O0C, dependmg upon the size of the glass art- cle being produced and the actual glass/crystal composition.

There are two main methods of maintaining and controllulg the temperature of the glass within the feeder chamber:

One method that is used to maintain the temperature of the chamber, and hence the glass inside, is by wrapping external electrical heating elements around the outer walls of the ceramic.

Pkatimm Metah Rey., 2002,46, (4) 184

Some Parameters of Platinum Materials Used in the Glass Industry

This form of heating is known as 'indirect heating'. The second method, commercially known as

direct heated platinum systems (DHPS@) (5), uses free-standing platinum alloy tubes welded together to form the T' section feeder chamber described before. These tubes contain and distribute the glass, and also control the temperature. Large electrical currents are passed through the platinum alloy, utilising the resistance/resistive heatmg effect to convert the electrical energy to heat. By using a control loop to adjust the current, the temperature can be precisely controlled.

The reason that two very similar but funda- mentally different technologies continue to exist for this application is because each system has its own strengths and weaknesses and the crystal/ glass producers choose the version that best suits their partic& requirements.

Indirect Heating of Platinum Clad Systems

An indirectly heated ceramic feeder system, clad with platinum (alloy), will enjoy the excellent glass corrosion protection that platinum (alloy) offers. However, the chamber walls in the vertical section of the chamber can be subject to collapse due to suction from the viscous glass melt as the reciprocating screw-plunger makes the upward stroke. In order to combat this, the vertical section could be strengthened, but to be effective the amount of platinum (alloy) required would have to be significantly increased.

In addition, after prolonged exposure to the high temperatures of glass forming, grain growth of the platinum (alloy) microstructure can weaken the mechanical strength of the material to such an extent that the chamber ruptures.

With this indirect heating configuration, the response time is relatively slow as the heating elements are on the outside of the ceramic and the heat has to be transmitted through the body of the ceramic chamber. This method does not give the level of control that the direct heating option allows.

Indirect Heating of Am."M Platinum Coatings

A ceramic feeder system that has been ACT* platinum coated will similarly enjoy excellent corrosion resistance but will use a much smaller

Schematic of an indirect1.y heated ACTTM coated,feeder chamber. The coating provides full protection to the ceramic against glass corrosion. The temperature is controlled via Kanthal@ electrodes outside the ceramic bodv. Heat travels through the cerumic to reach the glass

amount of platinum to do so. It will also utilise platinum rather than platinum-rhodium alloy. The excellent bond between the coating and the substrate removes the danger of suction collapse. Grain growth within ACTm platinum coatings is minimal (6) and due to the support of the ceramic substrate is thus of much less consequence. However, the heating method has the same limitations in temperature control as the clad version, because in both these cases the heat source is on the outside of the ceramic.

Direct Heating of Free-Standing Platinum Fabrications

If the platinum dad+ or liner is directly heated, the component providmg the heating effect is in immediate contact with the glass. This results in a much more responsive system with an increased level of temperature control.

However, fabricated direct heating systems are subject to the same mechanical issues as the indirectly heated dadded version: suction collapse, large numbers of welds, grain growth, etc., and similar quantities of platinum-rhodium alloy will

Phhmm Metah Rev., 2002,46, (4) 185

also be needed. In practice, the choice is between just two of the above options. The majority of the indirect heating systems supplied to high-quality crystal producers are now ACTm coated rather than clad. However, within the industry, there are still manufacturers who continue to choose fabricated direct heating systems because they feel that the precise temperature control offered by this system outweighs the advantages of the coated system.

Power CoatingsTM Combining the Advantages

Power Coatingsm were developed in order to provide the advantages of both systems and eliminate the drawbacks. Power CoatingsTM is a combination of the DHPS@ and ACTm coating technologies. An ACT^ platinum coating is applied to a ceramic substrate which is then direa- ly heated in the same manner as the solid platinum fabrications used in the traditional DHPS@ systems. As well as providing the beneficial features of both systems, it provides additional benefits such as increased responsiveness and hgh power capabilities.

The temperature control achievable within a chamber that has Power Coatingsm is extremely precise. To monitor the temperature, thermocouples are embedded in the ceramic immediately adjacent to the coating. These supply accurate temperature data to the computer control loop that automatically adjusts the power applied to the coating, thus controlling the temperature. The power applied is from a low voltage, high current (AC) source. The connection to the coating is made via specially-designed power distribution flanges which ensure an even current distribution around the chamber.

The temperature profile within the feeder itself can be specified by careful design of the coating thickness over the interior of the chamber. The heating effect of any section of the feeder chamber will be determined by the resistance of the coating in that section. The resistance is controlled by the geomeuy of the individual sections and by the thickness of the applied coating. By careful variation of the coating thickness, a constant heating profile

Schematic of a feeder chamber using Power Coatings" protection. The ACT'M coating shields the ceramic from glass corrosion and also controls the glass temperature. The heating surface is in direct contact with the glass thus giving a higher degree of temperature control

can be obtained over varying chamber dimensions. The heated coating is in direct contact with the

glass and its temperature is constantly monitored. This provides a very responsive feedback loop that allows accurate temperature control. Tolerances of k 0.5OC at operating temperature ranges of 1000 to 1200°C are currently being achieved.

Accurate temperature control provides control over the viscosity of the molten glass. Having accurate control of the glass viscosity, particularly at the point it is delivered to the moulding machines, is a key benefit to an automated glass manufacturer. For automated production, a critical operational parameter is the variance in the weight of the discrete quantities of molten glass (gobs) that are delivered to the mouldmg machines to form individual glass articles. This parameter is referred to as 'gob weight variance'. If the viscosity is under control then the gob weight can be controlled by careful regulation of the screw- plunger stroke. Ideally, the gob weight variance should be as close to zero as possible. The variance in gob weight that has been obtained with existing

Phtinum Metah Rev., 2002,46, (4) 186

A vie\\- looking dowri into LI

Power Cocrtings" chamber during in i t id hear-up. No glass is present iri the chamber at this point: the jilow- is from the pltitinum conting. The chamber is running lit about 1200°C nnd this temperature was achieved with power being upplied on1.v to the coating. N o other heot source was required

Power Coatingsm systems, such as that used by Crystalex, No* Bor, Czech Republic, is less than 0.2 per cent. This tightly-controlled delivery weight contributes towards the increased quality of the product and to a reduction in the rejection rate by ensuring that the correct weight of glass is consistently transferred to each mould, thus facili- tating smooth, efficient operation of the glass forming machines.

There are now four standard designs of feeder chambers that use Power C o a q m . The chambers have volumes ranging from 8000 to 24,000 cm3 and are able to deliver glass at temperatures up to 1400°C. These chambers are suitable for deal- ing with the existing range of daily pull rates and gob weight delivery requirements for the vast majority of current indirectly and directly heated feeder systems.

Conclusion Glass technology is one of the oldest manufac-

turing technologies. While using almost the same basic constituents now, as in the earliest times (for ornaments and utensils) the technology of production has advanced to the stage where manufacturers are able to produce perfect flat glass, lenses and display screens. Modem developments in the materials of production have contributed to this advance, and with the efficiency and accuracy available with Power Coaangsm technology, even more predictable outcomes are possible.

References 1 www.noble.matthey.com/pdfs/Engl1sh/37.pdf 2 D. R Coupland, Phtinwn Metah Rey., 1993,37, (2),

62; D. R Coupland, R B. McGrath, J. M. Evens and J. P. H d e y , ibid, 1995,39, (3), 98

www.noble.matthey.com/product/detail.asp?id=2 3 Takenfrom:

4 www.platinum.matthey.com/prices/ 5 www.eglass.de/ 6 M. Doyle, P. Williams, D. Coupland and J. Jenner,

Znt. G b s I., 1999, auly-August), 102

The Author Paul Williams is the Product Specialist for ACTTM coatings and platinum fabrications for the glass industry at Johnson Matthey Noble Metals, Royston. He has worked with the glass industry for the last six years, was involved in developing Power Coatings"" technology, and now Power Coatingsn and ACT" products.

Electrically Induced Phosphorescence When the voltage applied to a poly(pam-phenylene)

ladder-type polymer being tested for LED use was switched off, a team of researchers in Germany and Austria (J. M. Lupton, A. Pogantsch, T. Piok, E. J. W. List, S. Pad and U. Scherf, Pbs. Rey. Lett.., 2002,89, (16), 167401) saw a long-lasting pink phosphorescent glow (h - 600 nm) instead of the expected, but shorter lasting,

blue-green fluorescence (3L - 450 nm). Very low concentrations (- 80 ppm) of Pd atoms left over from the process catalyst and bound to the polymer backbone are

thought to be responsible for this new effect. Large numbers of dark long-lived triplet states gener-

ated in the polymer by the electrical excitation may diffuse thermally through the polymer fjlm until they encounter a Pd site where they decay as phosphorescence.

Platinum Metah b., 2002,46, (4) 187

ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES Microstructure and Shape Memory Behavior of Tisl.2(Pd27.0Ni21.8) and Tirs.s(Pdz8.sNi22.0) Thin Films T. SAWAGUCHI, M. SAT0 and A. ISHIDA, Muter sd. Eng., A, 2002,332, (1-2), 47-55

Ti-rich (Ti51.z(Pdz7.,,Nizl.8)) (1) and near-equiatomic ~i,p.5(Pd,.5Niu.o)) thin films were annealed at 773, 873 and 973 K from the amorphous state. At < 973 K, these crystallisations are effective for grain reline- ment. Film (l), annealed at 773 K, has line plate-like TizPd-type precipitates with a diameter < 100 nm inside the B2 grain. The shape memory characteristics can be improved by precipitate hardening.

Hydrogen Absorption of Nanoscale Pd Particles Embedded in ZrOz Matrix Prepared from Zr-Pd Amorphous Alloys S. YAMAURA, K SASAMORI. H. KUILTRA, A. INOUE, Y. C. ZHANG andu. ARATA, J. Matm a s . , 2002,17, (6), 1329-1334

Nanoscale Pd panides in an isolated dispersed state embedded in ZrO, matrix gave maximum Hz absorption amounts of - 2.4 mass% (Hz/Pd) at 323 K and 2.2 mass% (H*/Pd) at 423 K with Hz pressure of 1 h4Pa. In contrast, Pd metal in bulk and powder forms gave only 0.7 and 1.2 mass%, respectively.

CHEMICAL COMPOUNDS Multinuclear Magnetic Resonance Studies of the Aqueous Products of the Complexes cis- and trans-Pt(Ypy)z(N03)2 Where Ypy = Pyridine Derivative F. D. ROCHON and c. TESSIER, Can. 1. Chem., 2002, 80, (4). 379-387 The product of the cis title complexes undergoing

aquation in acidic pD was &~t(Ypy)~(DzO)z]~’, whereas hydrolysis in basic medium gave cis- Pt(Ypy)z(OD)z. Complexes containing 2-picoline and 2,4-luti&e ligands behaved differently in their 195Pt NMR due to the ottho effect. The trum analogues showed two signals in acidic pD corresponding to the diaqua monomer and the monohydroxo-bridged aqua dimer. Two species were also observed in basic pD.

Nonradical Trapping Pathway for Reactions of Nitroxides with Rhodium Porphyrin Alkyls Bearing PHydrogens and Subsequent Carbon-Carbon Bond Activation K w. MAK, s. K YEUNG and K. s. CHAN, Organometd’rcs, 2002, 21, (12), 2362-2364

A novel nimxide-induced H atom abstraction and p-elimination of Rh porphyrin alkyls was demonstrated. Subsequent C-C bond activation of methyl- substituted nitroxides by the R h o porphyrin radical yielded Rh porphyrin methyl complexes.

Liquid-Crystalline Materials Based on Rhodium Carboxylate Coordination Polymers: Synthesis, Characterization and Mesomorphic Properties of Tetra(alkoxybenzoato)dirhodium(ll) Complexes and Their Pyrazine Adducts M. RUSJAN, B. DONNIO, D. GUILLON and F. D. CUKIERNIK, Chcm. Ma&., 2002,14, (4). 1564-1575

Rhz(x,y,x-BmOCn)4 (B = benzoate group; m = n u - ber of akoxy chains on the aromatic ring; X,J ? = their anchoring positions; n = number of C atoms in each akoxy chain) and their pyrazine adducts (with polymeric structure via connected metallic centres) were synthesised. Most exhibit LC columnar and cubic mesophases with melting transition temperatures dose to or below room temperature. The equatorial llgands of the adducts fdl the interdimeric space.

Piano-Stool Inversion in Arene Complexes of Ru(ll): Modelling the Transition State T. J. GELDBACH, P. S. PREGOSIN and A. ALBINATI,]. Ckm. JOG.,

Dalton Trans., 2002, (12), 2419-2420 puH(yne)(Binap)]CF,SO, (arene = @-benzene

(1) or -toluene) was prepared. The structures were markedly distorted from a classical three-legged piano-stool structure with (1) having the P-Ru-P plane - perpendicular to the plane of the arene. The smucture of (1) indicates a transition state leading from one diastereomer to another via inversion at Ru.

ELECTROCHEMISTRY Degradation Mechanism of Long Service Life Ti/lrO2-Ta2O5 Oxide Anodes in Sulphuric Acid J. M. HU, H. M. MENG, J. Q. ZHANG and c. N. CAO, Corns. Sci., 2002,44, (S), 1655-1668

anodes over the whole of their electrolysis time in HzSO~ established that their performance can be divided into ‘active’, ‘stable’ and ‘deactive’ regions. In the first two stages, the loss of coated oxides is dominated by dissolution of the active component ( I r O z exhibits preferential loss). In the ‘deactive’ region, the oxide coatings are lost mainly by peeling at the Ti/oxide layer interface region.

Ageing studies of Ti/700/, IrOz-30%

Preparation and Electrochemical Characterization of Ti/Ru,Mnl-,O2 Electrodes J. L. FERNANDEZ. M. R. GENNERO DE CHIALVO and A. c. CHIALVO,]. E/e&uchem., 2002,32, (5), 51S520

DSA@ type electrodes of Ru-Mn mixed oxides (30 I at.% Ru < 100) supported on Ti were prepared by spray pyrolysis. Polarisation curves were used to evaluate their behaviour as anodes for the Clz and 0 2

evolution reactions. A composition of - 70 at.% Ru gave the best electrocatalytic activity and stability.

Plafinnm Metah b., 2002,46, (4), 18%191 188

j. APPL.

tA2oS

APPARATUS AND TECHNIQUE The Singlet-Triplet Energy Gap in Organic and Pt-Containing Phenylene Ethynylene Polymers and Monomers A. KOHLER, J. S. WILSON, R. H. FRIEND, M. K. AL-SUTI, M. s. KHAN.A GERHARD and H. B&LER,J. C h . Ply., 2002, 116, (21), 9457-9463

The evolution of the TI triplet excited state in a series of phenylene ethynylene polymers (1) and monomers with Pt atoms in the polymer backbone and in an analogous series of all-organic polymers (2) with the Pt(lI) tributylphosphonium complex being replaced by phenylene was studied. The Pt increases spin-rbit coupling so the TI state emission @hos- phorescence) is easier to detect. For both (1) and (2), the TI state was at a constant separation of 0.7 f 0.1 eV below the singlet .Y, state.

The Effect of pH on the Emission and Absorption Spectra of a Ruthenium Complex J. c. ELLERBROCK, s. M. MCLOUGHLIN and A. I. BABA, Inotg. Cbem. Commnn., 2002,5, (S), 555559

The protonable ligand for the Ru(1,lO-phenanthro- line)~(3-carbethoxy,4-hydroxy-l,lO-phenanthioline)~+- (PF& complex (1) is readily prepared. (1) has a small spectrophotometric change that results in a large emission intensity change. The emission intensity of (1) is pH dependent in the pH range S11. (1) is useful for luminescence-based pH sensors.

ELECTRODEPOSITION AND SURFACE COATINGS Crystallographic and Electrical Properties of Platinum Film Grown by Chemical Vapor Deposition Using (Methylcyclopentadienyl)trimethylplatinum M. HIRATANI. T. NmATAhlE, Y. MATSUI and S. KIMLTRA, Tbin SoMFihs, 2002,410, (1-2), 2W204

Pt thin films (1) grown by CVD using MeCpPtMe, were found to contain 0 and C impurities. The C impurities produce a micrograin morphology that contributes to hgh residual resistivity. High 0 contamination is observed, irrespective of the Oz/Ar ratio during growth. The intrinsic electrical transport prop- erty is not affected by the contaminants. (1) grown under oxidative conditions have good electrical properties so are useful as electrodes for MIM capacitors.

Electrodeposition of Osmium T. JONES, Met. Finfib.., 2002,100, (6), 84,8690

The electrodeposition of 0 s is reviewed. The &- line process, hexachloro-osmate process, nitrosy1 complex process and molten salt process are described. Blackening of the 0 s deposit for the hexachloro-osmate process is prevented by the use of dual anodes inside and outside a large porous pot. Very limited data on the deposit properties are available. Details of applications, alloys, analytical control techniques and toxicity are included. (19 Refs.)

Polysilicon Mesoscopic Wires Coated by Pd as High Sensitivity HP Sensors A. TIBUZZI, C. DI NATALE, A. D'AMICO, B. MARGESIN, S. BRIDA, M. ZEN and G. SONCINI, sens. Actnutors B, Chem., 2002,83, (1-3), 175-180

Mesoscopic poly-Si wires coated by a thin film of Pd (100 nm) can be used as HZ sensors. Using surface micromachintog combined with a usual microelec- tronic planar process, poly-Si wires of the following dimensions were fabricated 0.25-3.7 pm wide, 1OCL140 pm long, and - 600 nm thick. Because of their high surface/volume ratio, these wires exhibit a very hgh resistance percentage variation under HZ absorption.

CH4 Decomposition with a Pd-Ag Hydrogen- Permeating Membrane Reactor for Hydrogen Production at Decreased Temperature T. ISHIHARA, A. KAWAHARA. A. FUKUNAGA, H. NISHIGUCHI, H. SHINKAI, M. MIYAKI and Y. TAKlTA, Ind Eng. Cbem. Res., 2002,41, (14), 3365-3369

The C& decomposition reaction into C and Hz over Ni/Si02 was investigated using a Pd-Ag Hz-permeating membrane reactor. Removing the formed H2 with the Pd-Ag membrane increases the CH, decomposition activity (> 88Yo) at < 773 K. A higher H2 permeation rate was achieved with 77Pd-23Ag than with 9OPd-lOAg, thus increasing CH, conversion. The Hz formed was > 99.99% pure.

HETEROGENEOUS CATALYSIS Deep Oxidation of VOC Mixtures with Platinum Supported on A1203/AI Monoliths N. BURGOS, M. PAULIS, M. M. ANTXUSTEGI and M. MONTES, Appr Cat& B: Envimn., 2002,38, (4). 251-258

Pt impregnated metallic monoliths (1) were prepared from anodised Al foils. The catalytic oxidation activity of (1) was tested for the VOCs: 2-propanol, toluene, methyl ethyl ketone, acetone and their mixtures. Complete oxidation was achieved except for 2-propanol, where acetone was found as an oxidation intermediate. Even if the adsorption of the VOC on the A203 is governed by its polarity, the reactivity is mainly affected by the competition of the 0 atoms chemisorbed on the Pt particles.

lsomerization and Hydrocracking of M e c a n e over Bimetallic R-Pd Clusters Supported on Mesoporous MCM-41 Catalysts s. P. ELANGOVAN, c. BISCHOF and M HARTMA", C&.! &ti., 2002,80, (1-2), 3540

Pt-Pd/AlMCM-41 (1) is superior to Pt/AlMCM-41 and Pd/AlMCM-41 for n-decane isomerisation. The use of (1) results in a &her Clo isomer yield at a sub- stantially lower reaction temperature. (1) has a better balance between the two catalytic functions, namely acid sites and metal sites.

Pkdinwn Metah h., 2002, 46, (4) 189

PHOTOCONVERSION

Laser-Activated Membrane Introduction Mass Spectrometry for High-Throughput Evaluation of Bulk Heterogeneous Catalysts A. NAYAR, R. LIU, R. J. ALLEN, M. J. MCCALL, R. R. WILLIS and E. s. SMOTKIN, Anal. Cbem., 2002,74, (9), 193s1938

LAMIMS has been used to evaluate catalysts such as Pt/Ce02-ZrOz under realistic conditions. The catalyst array is supported on C paper overlaid upon a silicone rubber membrane configuration in a variation of MIMS. The C paper serves as a heat- dissipating gas diffusion layer that allows laser heating of catalyst samples to far above the decomposition temperature of the polymer membrane that separates the array from the mass spectrometer vacuum chamber. A bulk catalyst array spot can be evaluated for activity and selectivity in as little as 90 seconds.

Catalytic Activity and Poisoning of Specific Sites on Supported Metal Nanoparticles s. SCHAUERMA", J. HOFFMA", V. JoH~QNEK, J. HARTMANN, J. LIBUDA and H.J. m m D , A n g e w . Cbem. Int. Ed, 2002,41, (14), 2532-2535

Molecular beam methods and time-resolved reflec- tion-absorption IR spectroscopy were combined in order to investigate MeOH decomposition on Pd nanoparticles/Alz03/NiAl(l 10) model catalyst. Two competing reaction pathways were observed: a rapid dehydrogenation to give CO and a slow C-O bond breakage to form C and hydrocarbon species. It was shown that C-0 bond breakage occurs preferentially at particle step and edge sites.

Hydrogenation of Phenol by the Pd/Mg and Pd/Fe Bimetallic Systems under Mild Reaction Conditions J. MORALES, R. HUTCHESON, c. NORADOUN and I. F. CHENG, Ind Eng. Chem. Rcs., 2002,41, (13), 3071-3074

Three Pd-catalysed zerovalent metal systems were able to hydrogenate phenol to cyclohexanol and cyclohexanone at room temperature and pressure. Treatment of aqueous phenol solutions (5.0 mM) with Pd (2.6 ppt m/m)/Mg (1.00 g 20 mesh) and with 0.53 g of 1/8 in. Pd (0.5%)/&0, in contact with 1.00 g 20 mesh Mg resulted in 74% and 24% destruction, respectively, of the reactant after 6 h. The Pd/AL,O, with M g system was greatly enhanced by 2% v/v glacial acetic acid, resulting in an 84% reduction of phenol with a C balance of 93%.

Self-Regeneration of a Pd-Perovskite Catalyst for Automotive Emissions Control Y. NISHIHATA, J. MIZUKI, T. AKAO, H. TANAKA, M. UENISHI, u KIMURA,T. OKAMOTO and N. HAMADA, Nutun, 2002,418, (6894), 16L167

X-Ray diffraction and absorption established that I~F~s-/C~n.tnPdonsO~ autocatalyst (1) retains hgh metal dispersion owing to structutal responses to the fluctua- tions in exhaust gas composition. As (1) is cycled between oxidative and reductive atmospheres, Pd reversibly moves into and out of the perovskite lattice.

H OM 0 G EN EO US CATALYSIS High-Throughput Screening Studies of Fiber-Supported Catalysts Leading to Room- Temperature Suzuki Coupling T. J. COLACOT, E. S. GORE and A. KUBER, otganometa&cx, 2002, 21, (16), 3301-3304

High-throughput screening of Ph3P-based polymer-supported catalysts such as FibreCatTM-l 001 and selected Pd/C catalysts gave nearly quantitative conversion of activated and unactivated aryl bromides in Suzuki coupling using EtOH/H20. The FibreCat catalysts did not leach Pd. Forpchloroacetophenone and 3-bromothiophene, coupling could be possible by tuning the FibreCat catalysts with t-Bu3P.

Palladium Catalyzed Oxidation of Monoterpenes: Novel Oxidation of Myrcene with Dioxygen J. A. GoNCALVES, 0. w. HOWARTH and E. v. GuSEVSKAYA, J. Moi. Cutul. A: Cbem., 2002,185, (l-z), 97-104

Myrcene C/-methyl-3-methylene-l,6-octadiene) can be efficiently and selectively oxidised by O2 in glacial acetic acid containing LiC1, with PdC12-CuC12. New monoterpenes with a cyclopentane skeleton, 3- and 4-(1 -acetoy-1 -methylethyl)-1 -vinylcyclopentene, were produced. These products have a pleasant scent with a flower or fruit tinge and have potential as components of synthetic perfumes.

Novel Synthesis of Fused lsoxazolidines via a Palladium Catalysed Allene Insertion-Intramolecular 1,3-Dipolar Cycloaddition Cascade Reaction T. AFTAB, R. GRIGG, M. LADLOW, v. SRIDHARAN and M. THORNTON-PETT, Cbm. Commun., 2002, (16), 175L1755

Aryl iodides react with allene (1 am) and nitrone in toluene at 120°C over 48 h in the presence of 10 mol% Pd(OAc)2, 20 mol% PPh3 and CSZCO~ to afford the correspondmg isoxazolidines in 5&77% yield. The synthesis is a one pot reaction involving a Pd catalysed allenation of the aryl iodide in combination with a nitrone cycloaddition, creating two rings, two stereocentres and one tetrasubstituted C centre.

Polymerization of Phenylacetylene Catalyzed by Diphosphinopalladium(l1) Complexes K LI, G. WEI, J. DARKWA and s. K. POLLACK, Mammokmh, 2002,35, (12), 457-576

Cationic bis@hosphino)Pd complexes were gener- ated in situ by the reaction of (dppQPdCl(CH3), (dippf)PdCl(CH3), (dppe)PdCl(CHj), (dppf)PdCL, (dippQPdC1, and (dppe)PdCl, (dppf = bis(dipheny1- phosphino)ferrocene, dippf = bis(diisopropy1phos- phino)ferrocene and dppe = bis(dipheny1phosphino)- ethane) with AgOTf. The dppf- and dippf-Pd complexes catalysed the polymerisation of phenylacetylene, whereas the dppe analogues formed phenylacetylene ohgomers. The htghest molecular weight polymer was obtained from a 1:l CHzCIz/CH,CN mixture at room temperature. This seemed to be the best conditions for polymerisation.

Phfin#m MetaLF Rev., 2002, 46, (4) 190

A Simple, Recyclable, Polymer-Supported Palladium Catalyst for Suzuki Coupling - An Effective Way to Minimize Palladium Contamination w.-c. SHIEH, R. SHEKHAR, T. BLACKLOCK and A. TEDESCO, Syntb. Commnn., 2002,32,(7), 1059-1067

Preparation of a polymer-supported catalyst (1) involved wet impregnation of a polymer-bound phosphine with PdClz in EtOH. (1) was used for Suzuki coupling. After each cycle (1) was recyclable with low Pd leaching. The Suzuki coupling of an aryl- bromide with ptrifluoromethylphenylboronic acid resulted in the synthesis of 2-aminotetralin, used in the treatment of epilepsy, stroke, and brain or spinal trauma.

1,3-Dipolar Cycloaddition Reactions of Carbonyl Ylides with 1,2-Diones: Synthesis of Novel Spiro Oxabicycles v. NAIR, K. c. SHEELA,D. SETHUMADHAVAN, R DHANYA and N. P. MTH, Tetrabednm, 2002,58, (21), 41714177

A facile 1,3-dipolar cydoaddition reaction of car- bony1 ylides with a range of 0-quinones afforded highly oxygenated spiro oxabicydes. RhZ(0Ac)Z was employed as the catalyst. The reactions were carried out in toluene at room temperature under an atmosphere of Ar. For 1,2-benzoquinones, the ylide preferentially adds to the more electron deficient of the two carbonyls of the quinone.

A Free Ligand for the Asymmetric Dihydroxylation of Olefins Utilizing One-Phase Catalysis and Two-Phase Separation Y.-Q KUANG, s.-Y. ZHANG, R. JIANG and L-L. WEI, Tehbednm Lett., 2002,43, (20), 3669-3671

A free bis-cinchona alkaloid derivative (1) was used as the hgand in the 0s-catalysed asymmetric dihydroxylation of olefins. (1) can be easily prepared. The molar ratio of (l)/olefh was 5%, which was much lower than that required for the corresponding soluble polymer-supported cinchona alkaloid ligands (1&25%). Yields of 89-93% and ees of 89-99% were achieved with (1). Repetitive use of (1) is possible without significant loss of enantioselectivity when a small quantity of OsO4 is added after each run.

The Oxidation of Alcohols in Substituted lmidazolium Ionic Liquids Using Ruthenium Catalysts V. FARMERandT. WELTON, Green chin., 2002,4, (2),97-102

Substituted imidazolium ionic liquids may be used as solvents for the oxidation of alcohols to aldehydes and ketones using ["PrqPuO,] (1) as the source of the metal catalyst. (1) was used in conjunction with either N-methylmorpholine-AJ-oxide or 0 2 as co- oxidants. Benzylic alcohols were oxidised to their aldehydes in good to excellent yields, whereas aliphatic alcohols required much longer reaction times and gave poor yields.

FUEL CELLS Fundamental Aspects in Electrocatalysis: from the Reactivity of Single-Crystals to Fuel Cell Electrocatalysts K. A. FRIEDRICH, K. P. GEYZERS, A. J. DICKINSON and u. STIMMING, J. E k m d Cbm., 2002,526525,261-272

Nanostructured Pt-Ru electrodes prepared by metal electrodeposition exhibited distinct characteristics regardmg CO oxidation due to a cooperative reaction mechanism involving CO surface mobility. For Pt- Ru/C catalyst, prepared by the sulfito method, at 25°C the mass activity increases with increasing catalyst mass loading I - 55 wt.%. Then a plateau in the mass activity vs. weight loading is reached. At 65"C, a maximum mass activity occurs at 60 wt.%.

Surface Properties and Physicochemical Characterizations of a New Type of Anode Material, La,_,Sr,Cr,_,Ru,OJ_s, for a Solid Oxide Fuel Cell under Methane at Intermediate Temperature A.-L. SAUVET, J. FOULETIER, F. GAILLARD and M. PRIMET, J. CataL, 2002,209, (l), 2534

The material Lal_~rxCrl_yRuyO~_g (1) gave no loss of Ru even after sintering in air at 11 00°C. The activity of (1) for CH, steam reforming in a CH,-rich atmosphere is similar to that of Ru metal. However, Ru loss during prehmary treatment and the agglom- eration of Ru particles during reaction were avoided.

ELECTRICAL AND ELECTRONIC ENGINEERING Effects of Si Interlayer Conditions on Platinum Ohmic Contacts for p-Type Silicon Carbide T. JANG, J. w. ERICKSON and L. M PORTER, J. Ekctmn. Muter., 2002,31, (5), 506-511

A study of Pt ohmic contacts with Si interlayers on ptype Sic was performed. The use of a Si layer decreased the specific contact resistance (SCR) relative to Pt contacts without Si. The SCR values were reduced further by: (a) the deposition of the Si layer at 500"C, @) the incorporation of B in the layer, and (c) the design of the PtSi layer thicknesses in a 1:l atomic ratio. The lowest average SCR value was 2.89 x R cm'.

Structural and Magnetic Properties of CoCrPt Perpendicular Media Grown on Different Buffer layers C. L. PLAlT, K. W. WIERMAN, E. B. SVEDBERG, T. J. KLEMMER, J. K. HOWARD and D. J. SMITH, J. Map. Map. Muter., 2002, 247, (2), 153-1 58

Thin buffer layers (- 10-15 nm) of Ta/Ru, Ta/Hf or amorphous (CoCrPt)Tau for growing CoCrPt film on gave media layers with high perpendicular coerav- ity (- 3 kOe). Coercivity was only 1.7 kOe with a Ta/Ti buffer. XRD rocking curves showed the highest degree of (0 0 0 2) texture with the Ta/Ru buffer. This buffer promoted local epitaxy with the media layer.

Pkdinm Metah b., 2002,46, (4) 191

10-4

NEW PATENTS EL E CTR 0 DEPOSIT I 0 N AN D S U R FACE COATINGS Film Deposition on Nanometre Structures IBM COW US. AppL 2002/0,090,458

Thin film is deposited on a nanometre structure without filling holes and trenches by coating with a aerogel material and a metallic seed layer, such as Pt or Pd acetylacetonate. The coating is combined with a supercritical fluid, such as sc-CO2, and a co-solvent, such as an alcohol. When the supercritical fluid is removed the coating solidifies into the thin solid film.

Chemical Vapour Deposition of Ruthenium Films APPLIED MATERIALS INC U.S. Patent 6,440,495

A method to deposit Ru 6 l m s via liquid source CVD uses vaporised bis(ethylcyclopentadieny1)Ru as the CVD source material gas at 100-300°C in a reaction chamber. An 0 2 source reactant gas is provided. The substrate comprises Ti nitride, TiAl nitride or Ta pentoxide at a temperature of - 100-500°C and has a seed layer of Ru, Ir, Pt, Ru oxide, Ir oxide, etc., on which the Ru films are formed. The Ru film can be used as an electrode in a MIM capacitor.

APPARATUS AND TECHNIQUE Thin Film Oxygen Sensor PANAMETRlCS INC WorkiAppL 02/42,?56

An Oz sensor operating at 30&350"C, comprises a crystalline Zr02 (1) sheet, and two porous Pt electrodes poisoned by Pb to a level that will inhibit cross sensitivity to reactive components, such as Hz. The Pt electrodes are arranged to induce superionic 0 transport along current paths in (1) at the electrode surface. Oz concentrations of ppb can be detected.

Optical Switching Device US. PHILIPS CORP U.S. e p l . 2002/0,089,?32

An optical switching device comprises a transparent substrate and a switching film of a hydride of Sc and Mg, and optionally Ni, Al, Cr, etc., covered with a Pd or Pt catalytically active layer, in contact with an electrolyte. When a potential or current is applied between two electrodes, a change in optical transmission is detectable. The hydride is electrochemically switched from a low-H, mirror-like composition to a high-H, transparent composition, and vice versa, by H exchange. The device can be used in an optical switching element or sunroof.

Electrochemical Light-Emitting Elements SHOWA DENKO KK Japanese &L 2002/0?5,001

An electrochemical light-emitting element (1) uses a Ru complex for its hght-emitting layer together with a high-polymer solid electrolyte and an electrolyte salt (1) has a hlgh performance and needs only a low driving voltage to produce hlgh ltght emission. (1) has superior stability, reliability, and low manufacturing costs.

Colouring Mater Sensitisation Type Solar Battery Cell DAINIPPON PRINTING Japanese AppL 2002/093,475

A colouring matter sensitisation-type solar battery cell is made from laminations of a transparent substrate, a mansparent electrode layer, a power generation layer, a back electrode layer and a back substrate. The back substrate is pattern-coated with a Pt paste to form the back electrode layer, then baked with a coating liquid of 6ne TiOz grains to form an oxide semiconductor film. The hlm is impregnated, dried, and carries a Ru complex pigment sensitiser. Highly efficient power generation is obtained.

Hydrogen Separating Membrane MITSUBISHI KAKOKI K Japanese Appl. 2002/119,834

The manufacture of a highly permeable HZ separating membrane (1) for separating HZ from a H2-

containing gas is claimed. (1) is made by forming a Pd-based thin film on the surface of a porous carrier, and then depositing a Pd alloy or a metal to be alloyed with Pd on the pinhole parts of the membrane. After heat treatment, when a Pd-metal alloy is formed, the pinholes are effectively closed, and HZ yield is increased. (1) is easily made.

H ETE R 0 G EN EO US CATALYSIS Ruthenium Perovskite Production NATL INST. MATER SCI. Eumpean AppC. 1,233,002 Ru perovskites of the type L&UO, (1) are pro-

duced by reacting an aqueous solution of La and Ru ions with a precipitate-forming liquid to coprecipitate hydroxides of La and Ru which are then heat treated. (1) may also be precipitated onto a carrier from a homogeneous solution containing La, Ru and urea. The coprecipitated hydroxides have uniform dispersion and the resulting materials are efficient catalysts.

Destruction of CO, VOC and Organic Emissions DEGUSSA AG WorkiAppL 02/34,371

A h g h performance catalyst (1) for the destruction of gaseous CO, VOC and halogenated organic emissions comprises a layer of Pt group metal deposited on an inert support. A washcoat into which the Pt is deposited consists of A l z 0 3 stabilised with LazO3, CeOz stabilised with ZrOz and Pr'OIl. (1) is promoted by S-containing compounds selected from Ptso3, HzS04, (N&)zSO4, TiOS04, Ti2(S04)3, etc.

Production of High Quality Oil Bases INST. FRANCAIS DU PETROL WoriiAppLr. 02/48,289-290

The simultaneous production of very high quality oil bases and middle distillates comprises successive steps of hydroisomerisation (1) and catalytic dewax- ing (2). (1) is performed in the presence of a Pt group metal catalyst deposited on an amorphous acid SiOz- & 0 3 support, with metal dispersion of - 20-100%. (2) occurs in the presence of a Pt or Pd catalyst and a molecular sieve selected from ZBM-30, etc.

Phiitzum Metah Rev., 2002,46, (4), 192-194 192

Catalytic Converter for a lean-Burn Engine JOHNSON MAlTHEY PLC U.S. Patent 6,413,483 A catalytic converter (1) for a lean-bum engine

comprises a supported two-layer catalyst. The first layer contains Pt, K and a Ba NOx storage component on a washcoat of a mixture of at least two of A l z 0 3 , CeOz and/or ZrO,. The second layer contains Rh on a washcoat of CeOz and ZrOz. (1) further has an interlayer of a Ba compound on a washcoat. (1) is more selective for catalytic reaction between NOx and/or nitrate with hydrocarbons and/or CO than for between hydrocarbons and/or CO with 0 2 . NOx can be reduced to Nz under constant lean to stoichio- metric conditions without the need for rich spikes.

Hydrogenation of Acetylenes UOP LLC U.S. Patent 6,417,419

Hydrogenation of 4C acetylenes in a liquid hydrocarbon stream that contains mainly butadiene is performed by contacting H2 and the hydrocarbon stream with B catalytic composite on an inorganic oxide support. The catalytic composite has an average, diameter of 5 800 p, with 2 70 wt% of Cu and actlvator metal Pt, Pd, Ni, Co, Mn, or their mixture, being finally dispersed on the outer 200 pxn layer of the support. The microsphere catalyst has much improved stability and selectivity compared to similar catalysts with particles of diameter - 1600 p.

Vapour Phase Carbonylation with Iridium and Gold EASTMAK CHEMICAL co U.S. Patent 6,441,222

A vapour phase carbonylation process produces carboxylic acids and esters from a gaseous mixture of lower aliphatic alcohols, ethers, esters, CO and ester- alcohol mixtures using a solid supported catalyst. The gaseous mixture includes a halide promoter, and also HzO and MeOH in a molar ratio of - 0.01:l to - 1:l. The catalyst may be C, activated C, pumice, A l z O 3 , etc., containing 0.01-10 wt% of Ir and Au each, preferably 0.1-2 wt.%. The catalyst also comprises another metal selected from alkaline metals, alkaline earth metals, Sn, etc. The carbonylation is performed at 100-350°C and a pressure of 1-50 bar absolute.

(S)-1 -Phenylpropylamine TOYO KASEI KOGYO Japanese &pL2002/088,031

(.li-l-Phenylpropylamine (1) is prepared by reacting (R)-1 -phenylpropyl alcohol with diphenylphosphoryl azide as an azidation agent in the presence of a base to provide (4-l-phenylpropyl azide (2). (2) is then subjected to a hydrogenating reaction in the presence of a Pd/C catalyst. (1) is produced in high quality and high yield.

Removing Carbon Monoxide MlTSUB1Sr-u HEAVY IND. Japunese AppL 2002/121,008

C O can be selectively reduced in a Hz-conmining gas, to - 10 ppm CO, by passing over a supported Ru metal catalyst at 60-350°C. Gas with an 0Z:CO molar ratio of 0.01-0.5 is introduced to the catalyst. The difficulty of 0 2 quality control is avoided.

C-C Coupling Reaction DSM NV Worki&L 02/57,199 A C-C coupling reaction between an optionally

substituted (hetero) aromatic bromide compound (1) and a second reactant, such as an aryl boric acid is claimed. The process was performed in the presence of an aprotic dipolar solvent, such as dimethylfor- mamide or N-methylpyrrolidinone, a base and a Pd salt catalyst. The ratio between the quantity of Pd present in the Pd salt and (1) is 0.00001~.1 molYo, preferably 0.014.1 molYo. (1) should contain at least one heteroatom chosen from N, 0 and S.

Acetic Acid and Methyl Acetate Production ACETEX CHIMIE WwklAppL 02/62,739

A continuous production of acetic acid and/or methyl acetate, based on carbonylation of MeOH, dimethylether, etc., is performed in a homogeneous liquid phase under CO. The catalytic system comprises Rh and a halogenated promoter, with HzO at > 14?h concentration. The process is gradually modified by adding an Ir compound. The system shifts from being a Rt-based homogeneous catalyst on its own to a catalyst based on Rh and Ir, or even Ir alone, without stopping the installation and reducing the H 2 0 content.

Ruthenium Alkylidene Catalysts for Olefin Metathesis WFORNLA INST. TECHNOL. U.S. Pafmt 6,426,419

Ru alkylidene complexes (PCy3)(L)CIzRu(CHPh) (l), where L is a triazolylidene ligand, are claimed. (1) show hgh olefin metathesis activity, which is much higher at lugher temperatures than that of the parent catalyst (FCy3)2C12Ru(CHPh) (2). When L is 1,3,4 aiphenyl-4,5-dihydro-lH-triazol-5-ylidene, (1) is able to catalyse the ringclosing metathesis of substituted dienes to give tetrasubstituted cyclic olefins in good yield. Additionally, (1) has a similar stability towards Oz and moisture as that exhibited by (2).

living Radical Polymerisation Initiator KURARAY CO LTD Japanese AppA 2002/080,523 A living radical polymerisation initiating system

applicable to a wide range of radically polymerisable monomers comprises a halogenopentamethyl cyclo- pentadienyl bis(miary1phosphine) Ru, an a-halogeno- carbonyl compound or a-halogenocarboxylic acid ester, and an amine. The system can easily and quickly produce a polymer with narrow molecular weight dismbution while controlhg the molecular weight.

Allene-Substituted Carboxylic Acid Ester DENKI KAGAKU KOGYO Japanese 4 L 2002/088,026

A pure allene derivative free from substituent on the terminal and with a malonic acid ester (with a 1 4 C stmight chain alkyl, a branched alkyl with secondaty or tertiary C, allyl, an aromatic hydrocarbon or butadi- enyl group) is produced us ing a Pd phosphine catalyst, and 2-chloro-1,3-butadieneadiene. The diene is reacted with a Na compound of a malonic acid ester.

Plornnm Metals Rm, 2002,46, (4) 193

H 0 M 0 G E N EO U S CATALYSIS

FUEL CELLS Platinum-Ruthenium Electrocatalyst NATL. INST. ADV. IND. TECHNOL

J@anese AppL 2002/075,384 Manufacture of an electrocatalyst (1) for an elec-

trode catalyst joint body in a solid polymer fuel cell (SPFC) involves attaching a Pt-Ru catalyst layer to the surface of a polymer electrolyte membrane. (1) has superior oxidation activity for CO and alcohols. The SPFC has h g h performance.

Hydrogen Generating Device MATSUSHITA ELECTRIC IND.]@anese AppL 2002/121,006

HZ is efficiently produced in a catalyst-containing Hz generating device by suppressing catalyst deteriora- tion due to S. The Hz is produced by contacting a feed fuel, such as natural g a s or LPG that might contain a S-based compound as an odorant, HzO and air, with a Pt reforming catalyst. The catalyst also contains oxides of La, Ce, Al, Ga, Ti, Mg, Ca, Sr and/or Ba with Zr. The HZ can be used in a fuel cell.

ELECTRICAL AND ELECTRONIC ENGINEERING Surface-Metallised Pigmented Optical Body 3M INNOVATIVE PROPERTIES CO wOd&PL02/41,045

A colour-tailorable, surface-metallised, pigmented optical body comprises layered polymeric core(s) containing layer(s) of a thermoplastic polymer material. The thermoplastic polymer layers contain a dispersion of a particulate pigment such as C black, Fe oxides, etc. The metallic layer (1) comprises Pt, Ag, Au, Al, Cu and/or Ni, etc., at the outer surface(s) of the polymeric core (2). The transmission spectrum of the optical body differs from those of ( 1 ) and (2). The tinted polymeric films are used to provide neutral or coloured tint, in display devices, mirrors or other optical equipment.

Thermoelectric Device IBM CORP WodAppL 02/47,178

A thermoelectric device includes an electrical Pt conductor (1) thermally coupled to a cold plate and also a thermoelement electrically coupled to (1). The thermoelement has a plurality of Ups to couple it electrically to (1). The tips provide a low resistive connection while minimising thermal conduction between (1) and the thermoelement. The device has improved efficiency and is used for cooling substances, such as integrated circuit chips.

Electroless Ni/Pd/Au Metallisation Structure FUP CHIP TECHNOLOGIES LLC Wod AppL 02/58,144

A Ni/Pd/Au metallisation stack is formed upon the connection pads of integrated circuits at the wafer level by electroless plating. The interconnection pads can be Cu or Al(1). The lower Ni layer bonds secure- ly to (1) and the intermediate Pd layer serves as an out-difhsion barrier for Ni. The upper Au layer can receive a variety of interconnect elements.

Ruthenium Oxide Film Formation GENERAL ELECTRIC CO U.S. Patent 6,417,062

RuOz f i lms , for the fabrication of stable thin film resistors for microcircuits, are made by forming an inorganic Ru-based hlm (1) on a substrate, and then thermally decomposing a portion of (1) by exposure to high-intensity radiation, preferably visible light. RuC1,.nHzO and Ru(I1I) nitrosyl nitrate are used as the precursors. The method does not require thermal treatment which heats the bulk of the substrate, so can be used for non-ceramic substrates in printed circuit boards and flexible circuits.

Top Spin Valve Sensor IBM CORP U.S. Patent 6,437,950

A top spin valve sensor includes an IrMn pinning layer formed by ion beam sputter deposition. The magnetoresistive coefficient of the spin valve sensor is increased by placing an IrMnO seed layer between a free layer of the spin valve sensor and a first read gap layer of the read head. The free layer is preferably a NiFe-free film located between the first and second CoFe-free films.

Ferroelectric Capacitor with High Ferroelectricity ROHM CO LTD U.S. Patent 6,437,966

A ferroelectric capacitor, with maintained hgh ferroelectricity, comprises a Si substrate on which is a Si oxide layer, a lower electrode of an Ir-Pt alloy, a ferroelectric layer and an upper electrode. An Ir oxide layer is placed on the Si oxide layer, followed by an Ir layer on top, then the ferroelectric layer. The It-Pt alloy of the lower electrode can be formed to correspond to the ferroelectric layer. 0 vacancy in the ferroelectric layer can be prevented.

Electrically Conductive Antireflection Film NIPPON ELECTRIC GLASS J@anese AppL 2002/071,906

An electrically conductive antireflection lilm (1) con- sisting of two layers is claimed. The first layer, of thickness 7&250 nm, contains at least one Pt group metal, Au and/or Ag, and their compounds, and a Co- containing inorganic pigment The second layer has a refractive index of 1.3-1.6. (1) is coated on a glass panel of htgh light transmittance for use in a cathode ray tube. (1) reduces reflected hght, enhances the contrast, and imparts superior antistatic performance and electromagnetic wave shielding.

MEDICAL USES Microelectrode Catheter for Mapping and Ablation C. R. BARD INC WodAppL 02/47,569

A catheter (1) for mapping and/or ablation, includes a metallic cap of Pt or Au with a plurality of apertures and electrode(s) disposed in each aperture. Electrodes may be paired, or arranged along the length or circumference of the cap. (1) is used to treat a heart condition by placing it inside the heart and mapping a region of the heart with the mapping electrodes on the catheter or ablation using an ablation electrode disposed about the mapping electrodes.

Phtinum Metals Rev., 2002, 46, (4) 194

NAME INDEX TO VOLUME 46 Page

Acres, G. J. K. 64 Adlhart, C. 87 Aftab, T. 190 Aizenshtat, Z. 138 Akao, T. I90 Akgerman, A. I76 Akporiaye, D. 40 Albinati, A. I88 Allen, R. J. I90 Al-Suti, M. K. 189 Anderson, C. 84 Angove, D. E. 86 Antxustegi, M. M. I89 Appleton, T. G. 166 Arata, Y. I88 Arends, I. W. C. E. 87 Armelao, L. 85 Armor, J. N. 25 Asbton, S. V. 2, 37, 64,

Blacklock, T. Blake, A. J. Blanco, C. Boaretto, R. Bockris, J. O’M. Bolton, E. Bonnemann, H. Bontempi, E. Borguet, E. Borovkov, V. V. Borowski, A. F. Bos, J. Bossmann, S. Bosteels, D. Boudjouk, P. Boyall, D. Brida, S. Brodil, J. C. Brown, S. D.

Page

191 140 138 85 15 39

I05 85

I06 85

Page

Chiodini, N. 85 Choi, J.-H. 88 Christensen, P. A. I07 Ci, Y.-X. 88 Claridge, J. B. I36 Clark, J. S. I40 Cliffel, D. E. 14 Clifford, A. A. 139 Colacot, T. J. 82,

180. 190 42 Cougnon, C. 39 Crabtree, R. H. 85 Crettaz, R. 27 Cserey,A.

I38 Cukiernik, F. D. 140 I89 86 Dadgar,A. 38 D’Amico, A.

81. 105, 187 Bruce,D. 137, 165 Atkinson, I. M. 39 Buchwald, S. L. 87 Attard, G. A. 86, I07 Burgos, N. 189 Avdjukhina, V. M. 169 Busch, R. 38

Cai, M.-Z. 41

Backvall, J. E. I66 Canevali, C. 85 Baiker, A. 40.41 Cant, N. W. 86, 138

Baba, A. I. 189 Campagna, S. 85

Baltruschat, H. 40 Bare, S. R. I40 Bartlett, P. N. 106, 168 Barton, J. K. 165, I66 Bassler, H. I89 Bates, F. S. 86 Bazan, G. C. 137 Beckmann, D. I37 Behm, R. J. 42 Bklanger, D. I05 Belokurov, A. P. I36 Bennett, S. 24 Bergkvist, K. 1 I5 Bergman, R. G. 166 Bessarabov, D. G. 40 Bessard, Y 87 Bettinali, L. 86 Beyer, L. 85 Bkziat, J.-C. I I5 Billova, S. 138 Bimberg, D. 42 Bischof, C. I89

Cao, C. N. Cardenas T., G. Carvalho, L. S. Castellanos, R. H. Castelli, S. Cawthorn, R. G. Chan, A. S. C. Chan, K. S. Chandler, K. Chang, W.-B. Chartres, J. D. Chaudret, B. Chauhan, M. Che, C.-M. Chen, D.-H. Chen, D.-Y. Chen, G. Chen, P. Chen, X. Chen, X.-M. Cheng, I. F. Chialvo, A. C.

Phtinmn Metah h., 2002,46, (4), 195-198

I88 84 40 88 86

I77 I80 188 106 88 39 42

I38 39 38 88

I37 87

137 I80 I90 I88

Danks, T. N. Darkwa, J. Davies, M. S. Day, M. W. De, G. S. De Clerq, B. de Vries, H. Dehm, C. Delmon, B. Deluga, G. A. Deng, G.-J. Depero, L. E. Derouane, E. G. Devillers, M. Dey, S. K. Dhanya, R. Di Natale, C. Di Pietro, C. Dickinson, A. J. Diez, F. V. Do Carmo Rangel,

Dolmella, A. Donnio, B. Douglas, P. Drent, E. Drew, M. G. B. Dudfield, C. Diirr, H.

M.

Eaton, K.

Eisenberg, R. Elangovan, S. P. Ellerbrock, J. C. Elustondo, F. Erickson, J. W. Ernst, S. Ertl, G. Evans, J.

94 Fackler, J. P. 2 Factor, B.

87 Falk, L. K. L. 40 Fan,Q.-H.

188 Faria, J. L. Farmer, V. Fernandez, J. L.

42 Feurer,R. 189 Figoli, N. 136 Figueiredo, J. L. 190 Flores,R. 84 Fojta,M. 38 Ford,M. E. 84 Forster, R. J. 87 Fouletier, J.

166 Frage,N. 42

138 14

180 85 65

138 39

191 I89 85

191 138

40 I36 188 137 I39 85 64 85

137

Pugc

I67 189 189 140 191 40

106 165

176 39

115 180 38

191 188 38 40 38

I76 138 23

107 191 38

Freund, H.-J. 24, I90 Friedrich, K. A. I9 I Friend, R. H. I89 Fu, X. I36 Fujii, T. I39 Fujishima, A. 84 Fukunaga, A. I89 Funabiki. T. 39

Gaertzen, 0. 87 Gaillard, F. 191 Gam boa-Aldeco,

M. 15 Gasteiger, H. A. 42 Gaudet, J. I05 Geldbach, T. J. 188 Gennero de Chialvo,

M. R. 188 Gent, C. 25 Gerhard, A. 189 Geyer, U. 42 Geyzers, K. P. 191 Ghosh, K. 41

195

Giesen, M. Gillies, J. E. Goddard, W. A. Goldberg, I. Goltsov, V. A. Golunski, S. E. Gonqalves, J. A. Gong, X. Gonsalvi, L. Gonzalez, F. GooBen, L. J. Gore, E. S. Goswami, J. Gottlich, R. Granger, P. Grasa, G. A. Gratzl, M. Grigg, R. Groat, C. G. Groth, A. M.

Page

106 86 87

I36 37

I68 I90 I37 87

138 41

I90 39

I39 40 41 40

I90 I80 39

Grove, D. E. 48, 92, 144 Grushko, B. Gu, Y. F. Guay, D. Gui, L. Guillon, D. Guo, J. Gusevskaya, E. V. Gut, D. Guttmann. M.

Ha, H.-Y. Habermiiller, K. Hagihara, T. Hahn, S. F. Hall, M. D. Halley, J. W. Halligudi, S. B. Hamada, N. Hamasaki, S. Hambley, T. W. Harada, H. Harkins, S. B. Harris, C. A. Hartmann, J. Hartmann, M. Hashimoto, M. Haubold, H.-G. Hauck, B. J. Haukka, M. Havran, L.

38 14

I05 I36 I88 86

190 136 85

88 40 39 86

166 106 86

I90 I40 84 14 38 86

I90 I89 I40 I05 138 38

I38

Hayes, M. Heeger, A. J. Helaja, J. Hemhury, G. A. Henley, W. H. Henry, C. R. Herber, R. Hesek, D. Hillier, A. C. Hillman, A. R. Hillmyer, M. A. Hirano, M. Hiratani, M. Hoffmann, J. Hofmann, P. Hogarth, M. P.

Holmberg, K. Honda, K. Hong, N.-K. Hong, S.-A. Honma, Y. Hope, E. G. Horikosi, K. Hou, G. Howard, J. K. Howarth, 0. W.

Hu, J. M. HSU, Y.-N.

Hu, R.-H. Hu, S.-W. Hu, Y. Huang, T.-C. Hucul, D. A. Hutcheson, R.

Iggo, J. A. Ihm, S.-K. Ikariyama, Y. Ikuine, M. Inabe, T. Ingelsten, H. H. Inoue, A. Inoue, Y. Intini, F. P. Ishida, A. Ishihara, T. Ito, H. Ito, M. Itoh, K.

Page

73 I37 I39 85

136 24 40 85 50

107 86

136 189 190 87 3.

117. 146 I I5 84

I40 88 87

I66 86

I40 140, 191

190 140 188 41 88 87 38 86

190

167 138 86

136 39

115 188

85, 87 136 188 189 87

106 I40

Jaaskelainen, S. James, B. R. Jang, T. Jenkins, D. J. Jensen, S. F. Jiang, J. Jiang, R. Jirsa, M. Jobst, B. Johhek, V. Johnson, W. L. Johnston, P. Jollie, D. M. Jones, T. Jusys, 2.

Kakiuchi, N. Kalck, P. Kamer, P. C. J. Kamigaito, M. Kanai, T. Kang, S.-Y. Kani, I. Kanki, K. Kanta, A. Kasko, I. Katsnelson, A. A. Kawahara, A. Kell, D. R.

Pugr

38 167 191 86 40 85

191 42 42

I90 38 86 64

189 42

26 38 41

140 I37 I40 I76 I40 88 42

I69 I89 23

Kelland. L. R. 165. 166 Keller, L. P. Kempen, A. T. W. Kenna, J. Keresszegi, C. Khaire, S. S. Khan, M. S. Kiener, C. A. Kihn, Y. Kim, H. Kim, S.4. Kim, S.-K. Kimura, H. Kimura, M. Kimura, S. King, D. Kingon, A. I. Kinney, W. A. Kitagaki, M. Kitamura, S. Kizek, R. Klaui, W.

I38 136 64 40 86

189 87 38 88

I40 I38 I88 I90 I89 24 42

I39 39 88

138 84

Pqc.

Klein Gebbink,

Klemmer, T. J. R. J. M. 167

140, I9 1 Knowles, W. S. Kobayashi, A. Kohayashi, H. Kogan, V. Kohler, A. Kohno, Y. Koike, T. Kol, M. Komine, N. Komiya, S. Komori, K. Kondarides, D. I. Koper, M. T. M. Kopilov, J. Koshevoy, I. 0. Kousmine, R. N. Kramer, G. J. Kua, J. Kuang, Y.-Q. Kuber, A. Kucernak, A. Kuhnert, N. Kullavanijaya, E. Kumaradhas, P. Kuribayashi, K. Kurokawa, T. Kwon, B.-K. Kwon. K.-H.

Ladlow, M. Lan, X. Lang, H. Lawson, E. C. Layland, R. C. Le Bozec, H. Leclercq, G. Leclercq, L. Lecomte, J. J. Lee, S.-A. Leyarovska, N. Li, A.-D. Li, B. Li, K. Li, Q. Li, S. Li, X.-H. Libuda, J. Lima, C. A. S.

82 39 39

I38 189 39

I39 136 136 I36 140 24

107 136 38

I36 26 87

191 190 85

136 138 39 88 86 88

140

190 88 84

139 136 165 40 40 40 88

I40 88 85

190 38 86 39

I90 84

Pkafinnm Metah Rev., 2002,46, (4) 196

P c r p Page Puh'r

Limberg, C. 42 Mi, S. 38 Noyori,R. 82, 180 Primet, M. Lin, Z. 167 Miao, W. 85 Nozaki, K. Lindoy, L. F. 39 Michaels, W.C. 40 Ling, H.-Q. 88 Mickelson, G. 140 List, E. J. W. 187 Ming, N.-B. 88 Ocampo, A. L. Liu, D.-S. 180 Miranda, L. C. M. 84 Ohe, K. Liu, R. 140, 190 Misumi, Y. 140 Ohe, T. Liu, X. Liu, Z. Liu, Z.-G. Loiseau, F. Lopez-Castillo,

Lourdudoss, S. Lowe, M. P. Lu, B. Lubert, K.-H. Luci, D. K. Lukehart, C. M. Luo, L. Lupton, J. M.

Z. K.

Ma, H. Machik, P. Maciejewski, M. Macsari, I. Maeda, Y. Majhi, P. Mak, K. W. Makino, T. Mallat, T. Manners, I. Manor, E. Margesin, B. Mari, C. Markovic, N. M. Marsh, E. P. Martynov, M. I. Maryanoff, B. E. Masuda, H. Masuda, T. Matsuda, H. Matsuda, I. Matsui, Y. Mayor, M. McCall, M. J.

85 87 88 85

176 42 39

140 85

139 14 86

187

88 88

24.41 41 26 39

I88 I40 40

165 38

189 85 84

I07 136 139 84

I40 39

I40 189 137 190

Mittemeijer, E. J. Miyaki, M. Miyano, S. Miyoshi, Y. Mizuki, J. Mizumoto, S. Modica, F. Moisan, J.-F. Montes, M. Morales, J. Morazzoni, F. Moreira-Acosta, J. Moreno-Mafias, M. Mori, A. Mori, M. Moro, M. Moses, D. Motofusa, S. Muegge, B. Murakami, M. Muralidhar, M.

Nabatame, T. Nair, V. Naito, T. Nakato, Y. Nariki, S. Natile, G. Nawafune, H. Nayar, A. Neckers, D. C. Nelson, N. Ness, J. S. Neumann, R. Nichols, R. J. Ning, Y. Nishiguchi, H. Nishihata, Y. Nishimura, S.

McClenaghan, N. D. 85 Nishimura, T. McLoughlin, S. M. I89 Nishio, K. Meehan, G. V. 39 Nishioka, T. Meng, H. M. 188 Nolan, S. P. Meusinger, J. 25 Noradoun, C.

I36 189 87 39

190 137 140 41

I89 190 85 88 84

139 139 87

137 41 39 42 42

189 191 39 39 42

I36 I37 190 39 18 86

138 I07 108 189 190 73 26 84

137

Ohnishi, T. Oi, S. Okamoto, T. Oliva, R. Olsbye, U. Ordbiiez, S. Osakada, K. Ostrowski, J. C. Owen, G. R.

Pacifico, C. Padovano, G. Pakkanen, T. A. Palmqvist, A. Park, K.-W. Parkinson, B. A. Patil, S. Patterson, M. J. Paulis, M. Paulus, U. A. Pecchi, G. Pereira, E. C. Periana, R. A. PePina, V. Pesquera, C. Peter, L. M. Peters, J. C. Peters, W. Pettinger, B. Pieck, C. L. Pinkas, M. Pinkerton, A. A. Pinnow, C. U. Piok, T. Platt, C. L. Pleixats, R. Pogantsch, A. Pollack, S. K. Pollington, S. Popov, B. N. Porter, L. M. Poulston, S.

166 Pugh, R. I. Puntoriero, F.

88 41 Qiuhong, H. 41

139 87 Ralph, T. R.

190 84 Randle, J. 40 Rao,T. N.

138 Rath, N. P. 139 Rayner, C. M. I37 I67

136 136 38

I I5 88 39

187 86

189 42 40

137 87 88

138 15 38 84

106 40 38 39 42

187 191 84

187 190 24 88

191 24

Pugc

191 I39 85

I15

3, 117, 146

64 84

191 139

Reddy, A. K. N. 15 Reek, J. N. H. 41 Reichert, J. 137 Reiter, S. 40 Revkevich, G. P. 169 Reyes, P. 40 Rheinwald, G. 84 Richter, M. M. 39. 137 Robertson, J. I40 Robinson, M. R. I37 Rochon, F. D. I88 Rohr, F. 40 Rbnnekleiv, M. 40 Roper, W. I65 Ross, J. R. H. 41 Ross, P. N. 84 Rudi, A. 136 Ruffo, R. 85 Ruiz, P. 138 Ruiz, R. 138

Rytter, E. 40 Rusjan, M. I88

Sabo-Etienne,

Sadler, M. Sadler, P. J. Sakamoto, Y. Sandee, A. J. Sarto, F. Sasamori, K. Sastre, H. Sato, M. Sauvet, A.-L. Sava, G.

S. 42. 167 64

165, 166 84 41 86

188 138 188 191

165, 166 41.50 Pregosin, P. S. 167, 188 Sawagucbi, T. I88

190 Price, M. A. 86 Sawamoto, M. 140

Phfimm Mctuh Rev., 2002, 46, (4) 197

Puge

Scaglione, S. 86 Soudan,P. Schauermann, S. 190 Spjelkavik, A. I. Scherf, U. 187 Sridharan, V. Scherson, D. A. 107 Stammen, B. Schmid, G. 168 Steigerwalt, E. S. Schmidt, T. J. 42. 84 Stenzel, 0. Schramm, D. Schrobilgen, G. Schroers, J. Schuhmann, W. Schulz, R. Schumann, H. Schuth, F. Scotti, R. Searles, R. A. Sebastian, P. J. Segre, C. U. Seibt, M. Seita, M. Sengupta, P. S. Serp, P. Serroni, S. Sethumadhavan,

Shang, Z. Sharpless, K. B. Sheela, K. C. Shekhar, R. Sheldon, R. A. Shezad, N. Shi, J. Shieh, W X . Shilov, A. E. Shin, Y.-W. Shinkai, H. Shinmitsu, T. Shinoda, S. Silva, E. N. Simonet, J. Sinha, R. Skelton, B. W. Skoglundh, M. Slavcheva, E. Smith, D. J. Smotkin, E. S. Soderstrom, D. Sokolov, D. V. Someya, M. Sommer, F. Soncini, G. Song, C.-S. Sostero, S.

D.

84 165 38 40

105 42 25 85 27 88

140 42

137 84 38 85

191 88 82

191 191 87

139 140 191 25 39

189 140 139 84 94 84 39

I IS 40

191

Stimming, U. Stitzer, K. E. Sung, Y.-E. Sutton, D. Svedberg, E. B. Szabb, K. J.

Takahashi, S. Takei, 0. Takita, Y. Tanaka, H. Tanaka, T. Tang, Y. Tao, K. Tedesco, A. Teles, J. H. Terezo, A. J. Tessier, C. Thornton-Pett,

Tibuzzi, A. Tondello, E. Tong, Y. Y. Tosti, S. Toyama, S. Traverso, 0. Trevitt, G. P. Trimm, D. L. Tryk, D. A. Tung, C.-H. Tunik, S. P.

M.

Uemura, S. Uenishi, M. Unwin, P. R. Usami, R.

140, 190 42

136 86 Vad,T.

136 Vadgama, 189 P. M. 41 van Dijk, R. 85 van Ginkel, R.

Pkatinnm Metuh Rev., 2000,44, (4)

Pogr

I05 40

I90 I40 14 42

191 136 88 41

191 41

165 86

189 I90 39

I36 85

191 42

137 I88

190 189 85

I07 86 86 85

140 138 84 39 38

26.41 190 I37 86

105

12 139 I39

van Klink, G. P. M.

van Leeuwen, P. W. N. M.

van Oort, B. Venkert, A. Verpoort, F. Viciu, M. S. Villarroya, S. Violante, V. Viswanathan, R. Vogel, I. Volland, M. A. 0. von Hanisch, C.

I67

41 I39 38 87 41 84 86

I40 40 87

I37

Wakamatsu, S. 140 Waldofner, N. 105 Walker, A. P. 24 Wallnas, M. 42 Wang, C.-C. 38 Wang, C.G. 39 Wang, F. 39

Wang, S. 88 Wang, J.-X. 87

Wang, Y. I36 Waser, J. 87 Watson, D. J. 86 Weber, H. B. 137 Wei, B. 87 Wei, G. I90 Wei, L.-L. 191 Weinberg, H. 25 Wells, P. B. 86 Welton, T. 191 Wenkin, M. I38 Werner, H. 165 White, A. H. 39 White, K. W. P. 14. 26.

72. IIS, 180 White, P. 14, 17, 105.

107, 116. 176 Wieckowski, A. 88 Wierman,

K. W. 140. 191 Wild, B. 165 Willett, A. 64 Williams, D. E. 107 Williams, J. A. G. 165 Williams, P. 181 Willis, R. R. I90 Wilson, C. 140

Wilson, J. S. Wihiewski, M. Wisnoski, D. Wogerbauer, C. Wong, P. N. Workman, S. Wright, J. C. Wu, D. Wu, H. Wu, J. wu, L.-z. Wu, N. wu, x. wu, Y.

xu, x. xu, Y.

Yabut, S. C. Yae, S. Yamabe-Mitarai,

Yamakawa, T. Yamamoto, T. Yamaura, S. Yang, Y. Yasui, K. Yeung, S. K. Yoon, S.-G. York, A. P. E. Yoshimura, M. Yu, T. Yue, P. L. Yurechko, M.

Y.

Zawadzki, J. Zen, M. Zhai, Q. Zhang, C.-Y. Zhang, J. Zhang, J. Q. Zhang, K. Zhang, L.-P. Zhang, S.-K. Zhang, Y. C. Zhao, H. Zhao, M.-Z. Zhao, X. zur Loye, H.-C.

Prrgr

I89 86

139 41 84 39 66 88 85 38 39

I36 39 38

87 38

139 39

74 139 39

188 87 84

I88 42 65 84 88

I37 38

86 189 88 88

137 188 38 39

191 188 41 88 88

I36

198

SUBJECT INDEX TO VOLUME 46

a = abstract Acetates, methyl, from MeOH, a I39 Acetylenes, phenyl-, oligomerisation, a I90

polymensation, a 140. 190 Acid Chlorides, hydrogenation 73 Acrylic Acids, asymmetric hydrogenation I80 ACTm‘, Pt, Pt-Rh coatings, for the glass industry 181 Activation, CHJ. a 87 Alcohols, allylic, arylation, a 41

I40 aromatic. transfer dehydrogenation. a 40 2-arylcyclohexenols, to 2-arylcyclohexenes, a 139 methyl. conversion. to methyl acetate, a 139

decomposition, a 190 electrooxidation I06

DMFCs 88, 146 oxidation, a 42, 84

oxidation, (I 42,84. 191 aerobic 26 selective 24

from alcohols 26, 191 14

C-C bond formation, with enoxysilane, a

Aldehydes, from acid chlorides 73

Alfa Aesar, Fuel Cell Catalysts Brochure Alkali Metals. iodides. effects on Pd. Pt cathodes.

in superdry conditions Alkenes, dihydroxylation

Alkoxycarbonylation, chloropyridines, a Alkylacrylates, copolymerisation with ethene, a Alkynes, hydroalkenylation, a

from alkynes oxidation, a

hydroarylation, a hydrogenation hydrosilylation. a

Alloys, dental, a jewellery

Aluminium, Al-Mg-Pd, melt oxidation, a Al-Pd-Co. U-, V-phase, structures, a

Amination, aryl halides with an ammonia analogue Hartwig-Buchwald

Amines, in fast living radical polymerisation. a Amino Acids, L-DOPA synthesis Ammonia, oxidation, over Pt Aquation, cis-, trans-Pt(Ypy),(NO,),, a Arenecarboxvlic Acids. svnthesis. a Arenes, hydrogenation, h

iodo-. homocoupling, u Aroyl Halides, microwave-assisted phenylation, Aryl Halides? arylation, of allylic alcohols, a

cross-coupling reactions dehalogenation, a Heck reactions Suzuki couplings. a

Arylation, allylic alcohols. a a-amino acid esters, ( I

N-Arylation, aryl indolea Arylboronic Acids, coupling reactions Autocatalysts, technologies adopted by EU

94 24 73 39 87

139 I39 139 73

138 88 66 38 38 so so

140 82 24

I88 41

42. 138 I39

a 87 41 50 41

50, 139 190. 191

41 87 50

41.50 27

Biomimetic Assemblies, in photosynthesis, a Book Reviews, “Catalysis of Organic Reactions”

85 23

Catalysrs Q Cutalysed Reactions 65 “Handbook of Heterogeneous Catalytic Hydrogenation

“Modern Electrochemistry” 15 37

Buchwald-Hartwig Couplings 50 Bushveld Complex, PGE geology, conference I77

Cancer, drugs 88, 165. 166 Capacitors, container, with Pt films, for memory cells 107

MJPLZT/Pt. Pt/PLZT/Pt, H-damage. u 42

for Organic Synthesis” 73

“Progress in Hydrogen Treatment of Materials”

Page Page

88 MlM. Pt thin film electrodes, a I89 Pt/SrBiz zTa20u/Pt. annealing effects, a 88

Ru, a 87. 140 86

reforming of propane, a 41 supercritical, solvent 139, 165, 176

I06 copolymerisation, with ethene, a I39 effects in fuel cells 106, 117. 146 electrooxidation 84. 106. 191 poisoning, in PEMFC 118 reaction with Oz, a 40

41 41

in ketone synthesis, a 41 a$-, P.y-unsaturated, hydrogenation 82

23, 65. 73 conferences 23.24, 165. 167 heterogeneous, LI 4041.86, 138-139. 189-190 homogeneous, ( I 4142,87, 139-140, 19&191 in ionic liquids, a 191 low temperature fuel cells 3.64, 117, 146 in sc-COz 139, 165, 176

Catalysts, dendrimers 167. 180 in fat hardening 23

144 high purity gas production 144 homogeneous, supported 23 pgm/C, paste, powder, preferences 48 recycling 24.41. 176, 180. 190, 191 three-way, see Three-Way Catalysts

Catalysts, Iridium, Ir black, NOx reduction 24.41 Ru02/lrOz, to sustain H 2 0 electrolysis, in PEMFCs 132

Catalysts, Iridium Complexes, [ (~od)IrCl]~, a 140 [Ir(cod)(PPh3)JX, for C< bond formation, a I40 Ir(I), for hetero-Heck type reaction, a 139

88

OsO, + cinchona alkaloid, dihydroxylation 82, 191 OsO,/FibreCatTM, dihydroxylation 24

hydrogenation of arenes, a 138 LaFeCoPdO. for automotive emissions control. CI 190 Lindlar 73 Pd nanopanicleslAIZOJNiAl, MeOH decomposition, a 190 Pd-Bi/C. glucose selective oxidation, a I38 Pd-perovskite. automotive emissions control, (I I90 Pd-Pt/AIMCM-41, n-decane isomerisation, a I89 Pd/AI,O?, aromatic alcohol dehydrogenation, a 40

hydrodechlorination of chlorinated olefins, a 138 Pd/A1203 + Mg mesh, phenol hydrogenation, a I90 Pd/y-Al~O~,4-chloro-2-nitrophenol hydrogenation, a 86 PdAIMCM-41, n-decane isomerisation, a 189

73

Pd/bulk MgO single crystal, particle morphology 24 PdC. paste, commercial 48.92

liquid phase hatch hydrogenation 92

+ soluble Bi, glucose selective oxidation, (I 138 Suzuki coupling, a I90

Pd/CeOz/AI2O3, thiophene, VOC, oxidation, a I38 PdlFe, Pd/Mg, phenol hydrogenation, a 190

73

Pdsupport, aromatic alcohol dehydrogenation, a 40 PdC12-CuC12. myrcene oxidation, (I 190 transfer of oxide ions, to a catalyst substrate 165

Capacitors, (cont.) memory, Pt-PtO, thin film electrodes, a

Carbenes, Pd. N-heterocyclic nucleophilic so

poisoning, in PEMFC 122 Carbon Oxides, C02, methanation, a

CO, chemisorbed, on Pt, PtRu nanoparticles

Carbonylation, with aryltin compounds, a Carboxylic Acids, arene-, synthesis, (I

Catalysis, hook reviews

fixed bed reactors, design aspects

Catalysts, Osmium, Os,(CO),,Nulcan C. in PEMFCs. a Catalysts, Osmium Complexes,

Catalysts, Palladium, KsPPdWI,03.. 1 2H20/y-AII03. /C,

PdlBaSO,, hydrogenation of acid chlorides selective poisoning, with thioquinanthrenr 73

powder, commercial 48

PdPb-doped CaCO,, hydrogenation of alkynes modified with pyridine, quinoline 73

Pkatimm Met& b., 2002,46, (4), 199-204 199

Page

Catalysts, Palladium Complexes, n-allyl-Pd,

(-)-mesembrane, (-)-mesembrine. asymmetric synthesis of (-)-haemanthidine,

(+)-crinamine, (+)-pretazettine. a I39 (q'-aIlyl)Pd intermediate. allylsilanes cyclisation. a 41 for cross-coupling reactions SO. 165 (dippf)PdCI>, (dippf)PdCI(CH,), polymerisation. a 190 (dppe)PdCI?. (dppe)PdCI(CH>), oligomerisation, LI 190 (dppf)PdC12, (dppf)PdCl(CH,), polymerisation, ( I 190 FibreCatM, Suzuki coupling. a I90 N-heterocyclic nucleophilic carbenes. for C X . C-N 50 Pd, for poly@ara-phenylene) polymer. synthesis 187 Pd(0) tricyclohexylphosphine. coupling reaction. a 4 1 Pd-phosphino-oxazoline allyl, 'meta-dialkyl effect' 1 67 Pd-polymer-bound phosphine, Suzuki coupling. a 19 1 PdClz(Ph3P)>/dpph, alkoxycarhonylation. u 87 Pd(dba)? + phosphinobenzene sulfonic acid, a I39 Pd(dba)~/(trimethylphenyl)dihydroimidazolium salt, a 4 1 Pd>(dba)dphosphine, a-amino acid ester arylation. a 87 Pd(l1) acetate-pyridine/hydrotalcite, aerobic oxidation 26 Pd(I1) salt. carbonylation of aryltin compounds, a 41

41

Pd(OAc)? + phosphinohenzene sulfonic acid, a I39 Pd(OAc)? + PPh,, synthesis of isoxazolidines, ( I 190 Pd(OAc)? + P(o-tolyl),, for coupling reactions, a 139

Pd(OCOCF1)1/P(2-furyl)l, iodoarene homocoupling. a 139 Pd(PPh&C12. microwave promoted phenylation, a 87 Pd(PPh& unsaturated N-chloroamine cyclisation. a I39

24 electrocatalysts, anodes, for fuel cells 117. 146

3, 146 88

NHI oxidation 24 Pd-WAIMCM-41, n-decane isomerisation. a I89 Pt black. electrocatalysts, cathodes, for DMFCs I46 Pt-Rh/AI2O1, TWC, CO + Or reaction, a 40 Pt-Sn/AI20,. for cyclohexane dehydrogenation,

40 WA1201. Ce addition, phenol wet oxidation, a 138

for cyclohexane dehydrogenation, ri-octane

hydrocarbon oxidation. a 86 I38

+ Rh/Alr03, hydrocarbon oxidation. a 86 Pt/AI?OJAI monoliths, VOC oxidation. a I89 Pt/AIMCM-41, rr-decane isomerisation, CI 189 PtlC, 4-chloro-2-nitrophenol hydrogenation. ( I 86

hydrosilylation of alkynes, a 138 MeOH oxidation, a 42 NO decomposition, a 86 O? reduction reaction, a 42

PtlCeOr-ZrO?, in high throughput screening, (I 190 Pt/graphite, cinchona-modified, for hydrogenation. ( I 86 m i , Pt/Ru, Pt/Ru/Ni, nanoparticles, for DMFC. ( I 88 WSPE membrane, preparation. a 40 Wwide-pore SO2 , polystyrene hydrogenation, a 86 PtCr. PtFe, PtMn, PtNi, PtTi, PtZr, electrocatalysts,

cathodes. for PEMFCs 3 PtMo. electrocatalysts. anodes, for PEMFCs 117 PtRu, fuel cell electrocatalysts 14, 88, 106. 117, 146. 191

CO tolerance in fuel cells 106, 122 PtRu/C, fuel cell electrocatalysts 14, 117. 140, 146, 19 I Pt,Sn/Mg(Al)O, propane dehydrogenation, a 40

Catalysts, Platinum Complexes, Pt(hpym )CI2, 87

Catalysts, Rhodium, Pt-Rh/AI2O3. TWC. CO + O?, a 40 Rh aluminosilicate, laminar, zeolitic structures, a 138

anchoring [Rh(Me2C0),(2.5-norbornadiene)]C104, a 138 Rh/A1201, film, model catalyst 24

hydrocarbon oxidation. a 86 + Pt/ALO3. hydrocarbon oxidation. a 86

Pd(OAc)?, arylation of allylic alcohols. a Pd(0Ac):. for cross-coupling reactions 50

Pd(OAch/dppf, alkoxycarbonylation, n 87

Catalysts, Platinum, CH, partial oxidation

cathodes, for fuel cells nanoparticles. Pt, for DMFC, a

Pt/y-Al?03, preparation I 15

ti-octane reforming, n-pentane isomerisation. cr

reforming, n-pentane isomerisation. a 40

impregnated using H2PtClh, Pt(NH3)KI,, a

Pt(NH&CI>, for CH, activation, a

Pase

Catalysts, Rhodium Complexes, alknyl-Rh. aryl-Rh. a 87 with fluoroorganic groups. solubility in sc-COr I65 in fluorous phases 165 Rhz(OAc)r. for 1 ,3-dipolar cycloaddition. ( I 191 Rh-polymer. sc-CO? soluble 176 [Rh(A)CO]*/SiO2. hydrofortnylation-hydrogenation, a 4 1 [Rh-(-)-BINAP(COD)IClO,. in L-menthol process 82 [Rh(cod)(MeCN):]BF,, conjugate additions, a 87 [Rh((R.R)-DiPAMP)COD]BF,. L-DOPA synthesis 82 Rh(1). for hetero-Heck type reaction, a I39 Rh(1II) salt, carbonylation of aryltin compounds. a 41 [Rh(OH)(cod)],, for internal alkynes + silanediols. a 139 Rh(TAN,,DPPA)CI, cyclohexene hydrogenation 176

88 14, 88, 106. 117, 146. 191

106, 122 14. 117. 140, 146. 191

I39 methyl acetate formation. ( I 139

41 86

in PEMFCs 132

groups, solubility in sc-CO: 165 in fluorous phases 16.5 ["Pr,N][RuO,] + NMO or O?. alcohol oxidation, (I 191 permthenate</. ruthenateslFibreCat ' ~ ' , alcohol oxidation 24 [( RrP(CH2),,PR?-ffJXRu=CHR']+. olefin metathesis, ( I 87 Ru-BINAP. dendritic. asymmetric hydrogenation

180 sing enyne metathesis, CI 140

87 RCM of diolefins. (I 87

(PPh,),, fast living radical polymerisation. ( I 140 (xylylbinap)(diamine). ally1 alcohol synthesis 82

42 167

82 RuO,. with NaOCI, oxidation oferhers. o 87 IRU(OAC)~((S)-BINAP)]. (S)-(+)-naproxen synthesis 82 [RuX2(BINAP)]. for ketone hydrogenation 82 [RuX(arene)BINAP]X. for ketone hydrogenation 82

18 107. 189

precursors for 38, 107, 189 Chemiluminescence, see Luminescence Chirdl, catalysis. in hydrogenation. oxidation 82 Cisplatin 88, 165. 166 Clusters, Rh-Pt. a 38 Coatings, ACT'", Power Coatings'". for glass industry 18 I

see also Deposition and Electrodeposition Cobalt, Al-Pd-Co, U-. V-phase. structures. N 38

Pt-Co. jewellery alloy 66 Colloids, Ag. Pd. for Ag:Pd powder. ( I 84

Pt 105. 136 Combinatorial Chemistry, in catalysis 24 Composites, ceramic matrix. with Al-Mg-Pd. a 38

Pd-ceramic membrane. a 86 see also Nanocomposites

Conferences, 8th Int. Conf. Cheni. of the PGMs, Southampton, 2002 81. 165, 166. 167

177

SC. U.S.A., 2000 23 24

EuropaCat-VI, 2003 24 Fuel Cells for Automotive Applications, London. 2002 64 Fuel Cells - Science and Technology 2002.

Amsterdam, 2002 64 Thc Dynamic Electrode Surface, Berlin, 2002 I Oh

Catalysts, Ruthenium, Pt/Ru, Pt/Ru/Ni. nanoparticles, for DMFC, ( I PtRu, fuel cell electrocatalysts

CO tolerance in fuel cells PtRu/C. fuel cell electrocatalysts Ru-Sn/Y zeolite. MeOH conversion. ( I

Ru/AI?O1, COr reforming of propane. (1

Rdsepiolite, + Mn, Mo, Zr. for CO? methanation. a RuO?, RuOJIrO?, /TiO?, to sustain H1O electrolysis.

Catalysts, Ruthenium Complexes, with fluoroorganic

Ru Schiff base, Kharasch addition. CCI, + olefins. a

RuCI?, chlorination. aromatic compounds. olefins. (7 RuC11.3H20 + trioctylamine, lignin hydrogenation [RuH?(H?),(PCy,)?l. arene hydrogenation, a 42 Ru(l1) BINAP. chiral propdnediol production

CerOx"' Process, to treat hazardous organic wastes Chemical Vapour Deposition, Pt, films

nanoparticles, ri 38

9th Int. Platinum Symp.. Billings, MT, U.S.A.. 2002 18th Conf. on Catal. of Org. React.. Charleston,

EuropaCat-V. Limerick, Ireland. 200 I

RhRiO?, with propene, NOx reduction 24 Copper,-Pt-Cu, jewellery alloy 66

Pk~tinum Metah Rev., 2002, 46, (4) 200

Page PLI@

Electrodes, ( m i ? . ) TiRuO?, anodes, preparation, a I37 Ti/Ru,Mn, ~ ,01 anodes. CI2 + O2 evolution, a 188

Electroflotation, of wastewater. n I37 Electroless Plating, Ag-Pd thin films, for membranes, a 86

40 Emission Control, motor vehicles 27, 190 Erbium, Pd-Er-H. H effects on 169 Etching, Pt, by ICP, using BClKI?, a 140 Ethene, copolymerisation with alkylacrylates. a 139

non-alternating copolymerisation with CO, a 139 Ethers, cyclic enol, by ring-closing enyne metathesis, a 140

oxidation, a 87 Ethyl Pyruvate, hydrogenation, a 86 Europe, EU adopted emission control, legislation 27 Eutectic Reactions, Pd-rare earths 108

Films, Co-Pt, sputtered on (001)-oriented Si wafer, a 140 Ir, by MOCVD, a 39

107

2, 48, 92, 144 74

42,88, 140, 191 automotive use 24, 64 catalysts, Pt/C, for MeOH oxidation. a 42

42 PtRu. CO tolerance 106, 122

conferences 24, 64 DMFC, anodes 14. 146

cathodes 146 MEAs 146 miniaturisation 161 portable applications 161

191 191

14 14, 146

3.64, 117. 146 3, 117. 140. 146

Pt. on SPE membranes, a

Pt, by CVD, for memory capacitors see also Thin Films

'Final Analysis'

Fuel Cells, a Fracture, in Ir-based refractory superalloys

for 0 2 reduction reaction. in presence of C1-, a

electrocatalysts, Pt-RdC, by sulfito method, a electrodes. Pt-Ru, nanostructured, CO oxidation. a Fuel Cell Catalysts Brochure. Alfa Aesar HiSPECT" fuel cell catalysts low temperature, catalysis membrane electrode assemblies

Coupling Reactions, (arylboronic + carboxylic) acids, a 41 cross-. for C-C. C-N bonds 50 homo-, iodoarenes, a I39

Pd catalysts SO, 165 see also Heck Reactions and Suzuki Couplings

74 Crystallisation, P&Cu3,,PzoNi,o, a I36

Pd.IINil,Eu?IP211 melts, a 38 Cyclisation, allylsilanes, a 41

unsaturated N-chloroamines, to piperidines, a 139 Cycloadditions, 1.3-dipolar. a 190, 191 Cyclohexenes, 2-aryL. from 2-arylcyclohexenols, N 139

hydrogenation 176

Decomposition, CH,, a 189 MeOH. a I90 NO, ( I 86

Dehalogenation, aryl halides, a 41 Dehydrogenation, propane, a 40

transfer, aromatic alcohols, a 40 Dendrimers, as catalysts 167, 180

Os(ll), Ru(l1) polypyridines, photoproperties. a 85 synthesis 165

Dental, alloys, a 88 85

DHPS@, for the glass industry 181 Diesel, oxidation catalysts, Pt 27

particulate filters 27 selective catalytic reduction 27

Dihydroxylation, by OsO, 24, 82, I9 I P-Diketones, Pt(11) with AI(CH1),, for Pt networks 105

Pt(I1) P-diketonates, photoreactions with olefins, a 39 Dimerisation, of [M(L-L)?(eilatin)]'+, M = 0s. Ru, a 136

94 74

Electrical Conductivity, in (C,H1,NH)[Pd(dmit)2]2, a 39 Electrical Contacts, ohmic, Pd/n'-GaAs, a 88

Pt, with Si interlayers. o n p-type Sic, a 191 Electrochemical Cells, CerOxTM waste process 18 Electrochemistry, a 84-85, 137. 188

book review 15 94 18 85

189

organosilanes, as coupling agents 50

Creep, in Ir-based refractory superalloys

Deposition, Pd, at C paste electrodes, a see also Coatings and Electrodeposition

2,4-Dinitrotoluene, electron transfer reduction of Ductility, in Ir-based refractory superalloys

cathode reactivity of Pd, Pt, in dry DMF destruction of hazardous organic wastes doping, of Pt phthalocyanine microcrystals, a

Pt, fine particles. a 39

in fuel cells, see Fuel Cells Electrodeposition, 0s. 0 s alloys, a

see also Coatings and Deposition Electrodeposition and Surface Coatings, a 39,85, 189 Electrodes, Au, anchoring of Pt(l1) complex. a 137

Au-Pt black. for glucose sensor, a 86 C paste, Pd deposition and dissolution, a 85 conference 106 in fuel cells, see Fuel Cells

94 Pt( 1 1 I ) . for CO electrochemical oxidation 106

94 for CO electrooxidation 106 in hydrocarbon sensor, a 40 microdisk, in NO sensor, a 40 nanoparticles. + nano-honeycomb diamond films, a 84

189 wire. for in vivo biolo ical sensors 72

18 Pt-PtO, thin films. for memory capacitors, a 88 PtRu, for CO electrooxidation 106 Ru(001). electrooxidation I06 RuOK, in supercapacitors, a 88

39

TiflrOz-TaOs, anode ageing, in HzSOd, a 188 Ti/lr0,-Sb~O5-SnO1. wastewater electroflotation, a 137

Pd. cathode reactivity in dry DMF

Pt, cathode reactivity in dry DMF

thin films, for MIM capacitors, a

Pt-plated Ti, in CerOx"e1ectrochemical cell

n-Si. with fine Pt particles, CI

Ti2FeRu02, Ti,Fe,Ru,O,,, in supercapacitors I05

nanoparticles 3, 88, 117. 146 PEFC, Pt-Ru/C electrocatalysts, XANES. a I40

MEAs, ( I

anodes cathodes CO,, CO. poisoning comparison with DMFC electrocatalysts, anode, PtMo, PtRu

cathode, Os,(CO),JVulcan C, a

PEMFC, air bleed technique I40 129 117

117 I46 117 88

3, 88

Pt. Pt alloys 3 MEAs 3, 117 water electrolysis. effects 132

191 SOFC, LaSrCrRuO, anode material, a see also Catalysts, Iridium, Platinum, Ruthenium

Gases, high purity HI, Oz 144 Geology, book 17

conference I77 Glass, production technology 181 Glucose, oxidation 106, 138

sensors, CI 40, 86

Halogenation, of aromatic compounds, olefins, a 42 Heck Reactions 50, 139. 165 High Temperature, Ir-based refractory superalloys 74 High Throughput Screening Techniques 24, 87, 190 Hydroalkenylation, alkynes, with silanediols, a I39 Hydroarylation, alkynes, with silanediols, a I39 Hydrocarbons, emission control in EU 27

oxidation. a 86 sensor, a 40

Hydrocracking, n-decane, a I89 Hydrodechlorination, chlorinated olefins, a 138 Hydroformylation-Hydrogenation, 1 -octene, a 41

P&nm Metals Rev., 2002,46, (4) 201

P q r

37, 169. 188

P q r

165 85

Hydrogen, absorption, Pd book review 37 damage of capacitors. a 42electrooxidation 117 interaction with Pd. Pd alloys 37, 169 sensors, a 189 separation. using Pd-Ag membrane reactor. 189

solid solutions, in Pd structural changes in Pd, Pd-Er. Pd-W treatment of materials

a-(acy1amino)acrylic acids, esters alkynes arenes. a asymmetric, acrylic acids book review carboxylic acids, a$-. P.y-unsaturated chiral-catalysed cyclohexene ethyl pyruvate, a ketones lignin in liquid phase batch reactors 1 -octene phenols, (1

polystyrenes, a

using Pd-ceramic membranes, a 86

Hydrogenation, acid chlorides

Hydrolysis, cis-, rram-Pt( Ypy),(NOi),, a Hydrosilylation, alkynes. a Hydrotalcites, catalyst suppon

169 169 37 73 82 73

42. 138 180 73 82 82

I76 86

82, 138 I67

48.92 I76

86. 190 86

I88 138 26

Insulators, single-molecule, tram-Pt(I1) complex. u 137 Ion Source, high temperature, of Pd. a I36 Ion Transfer, IrCL-. across liquid interface, u I37 Ionic Liquids, solvents, a 191

39 Ir( 1 I I ) , surface, for electrolyte hydration I06 thin films, hy DC sputtering, a 42

74 Ir-Nb, Ir-Zr, Ir-Nb-Ni, Ir-Nb-Ni-Al 74 Pt-lr, jewellery alloy 66 superalloys. refractory: creep. ductility. fracture 74

137 IIr(DPF)ll. electrophosphorescence, a 137 luminescence 137. 165

137. 188 Ir02, thin films, by DC sputtering, ( I 42

Isomerisation, n-decane, (i 189 Isoxazolidines, synthesis. a I90

Jewellery, Pt, Pr alloys. welding by laser 66 18 1

3. 64. 117, 146 24, 190

Iridium, films, by MOCVD. a

Iridium Alloys, (Ir. Rh)75Nb15Ni10, specific strength

Iridium Complexes, IrClh?-, ion transfer. a

Iridium Compounds, electrodes. (I

IrOJPLZT/Pt, capacitors. a 42

Johnson Matthey, ACTn', Power CoatingsrM catalysis for fuel cells, research Fi breCat ' '' PGM Conference competition winners "Platinum 2002" Rhodium Bicentenary Competition, winner

Ketones, synthesis hydrogenation

Kumada-Tamao-Corriu Couplings

Lasers, to drill cavities in Pt wire electrodes

Lignin, hydrogenation Liquid Crystals, Rh carboxylate polymers, ci Luminescence, electrochemi-, Ir(ppy),. c/

Ru(bpy)<'*. a

welding of Pt jewellery

Ir terpyridyls Os(I1) polypridines. dendrimers. (1

photo-. Ir(ppy),, a Pt(I1) quaterpyridine, a Ru(bpy)<". a

Pt octaethylporphyrin, C I

166, 167 116

2

26.41. 191 82. 138

50

72 66

I67 I88 137

39, 137 165 85

137 39

137 137

Luminescence, ( c m i . ) Ru terpyridyls Ru(1I) polypridines. dendrimers. n

Macrocycles, Pd(ll). Pt(I1). N 39 Magnesium, AI-Mg-Pd. melt oxidation, a Magnetism, in CoCrPt perpendicular media, a

38 191

in CoCrPtB layers. on TiZr underlayers. (I 140 in SrCuRhO, SrNiRhO. a 136

Mass Spectrometry, differential electrochemical, a 42 laser-activated membrane introduction. LAMIMS, a I90

Medical Uses, (1 88 PGM Conference 165. 166

Melting Points, Pt, Pt alloys 66. 181 MEAs, in fuel cells 3. 117. 140. 146 Membranes, Pd-Ag, for CHI decomposition. a I89

Pd-ceramic, a 86 SPE, with Pt particles. a 40

Memory, capacitors for 88. 107 1.-Menthol, commercial synthesis 82 Metathesis, of olefins. RCM. ROMP. (I 87

ring-closing enyne. a 140 Methanation, CO.. a 86 Methane, activation, ( I 87

decomposition. ( I I89 partial oxidation 2 1 steam reforming. a 191

Microwaves, in phenylation of aroryl chlorides. a 87 in synthesis of [RuCp(dppm)SR]. a I36

MOCVD, Ir films, a 39 Myrcene, oxidation. ( I I90

Nanocomposites, Pd:Ag, physical properties, a 84 Pt-RdGCNF. for DMFC anodes 14 R u O K . supercapacitors, a 88 see also Composites

Nanocrystalline Powders, Pd:Ag. a 84 Ti,Fe,Ru~O,,. in supercapacitors 105

Nanocrystals, Pt-Ru. on GCNF 14 Nanoparticles, Pd, on AI201NAI. model catalyst, a 190

embedded in Zr02. H? absorption. a 188 in HOin-oil microemulsions. n 38 stahilised by polyfluorinated chains, ( I 84

Pt. 3D networks. Al-organic-stabilised 10s on y-Al,O,. catalysts I 15 on C nanospheres. a 38 with nano diamond films. as electrodes, a 84 preparation. ( I I36

in Pt. Pt alloys. fuel cell electrocatalysts 3, 88. 117. 146 Pt. PURL surface diffusion of cheniisorbed CO 106

Nanostructures, PGM Conference I65 Pt-Ru electrodes. for fuel cells. ( I 191

Nanowires, Pt, u I36 (S)-(+I-Naproxen, synthesis 82 Nitrogen Oxides, NO, decomposition, ( I 86

sensor. ci 40 NOx, adsorbera 27

reduction 24.41 selective catalytic reduction of diesel emissions 27

188 188

DeNOx, catalysts 27

Nitroxides, reactions with Rh porphyrin alkyls, (I NMR, multi-. aqueous products of Pt(Ypy).(NO,),, a Nobel Prize, Chcmistry, chiral-catalysed reactions.

Noril'sk, PGE geology. conference I77

I-Octene, reactions 41, 176 Ohmic Contacts, see Electrical Contacts OLEDs, Ilr(DPF)31 in PVUPBD. ( I I37 Olefins, dihydroxylation. asymmetric. N 191

as H acceptors. (I 40 Kharasch addition, of CCI,. a 87 metathesis: RCM, ROMP, ci 87 with Pt(I1) P-diketonates. photoreactions, (1 39

Oligomerisation, phenylacetylene. ( I I90

pgm catalysts 82

Phtiinun Metah Rev., 2002,46, (4) 202

Puge

Osmium, electrodeposition. a 189 Osmium Alloys, electrodeposition, a I89 Osmium Complexes, in glucose sensors. a 40

ground and excited states 106 luminescence, a 85 OS~(CO)P. pyrolysis, a 88 0s.bipy-modified DNA, voltammetric analysis. a 138 IOs(L-L),(eilatin)]'+. dimerisation, a I36

Osmium Compounds, osma-aromatics, osmabenzenes 165 OsO,, in DNA voltammetric analysis, a 138 Os(V111), oxidation state 165

24. 26.42, 84. 191 alkenes. ( I 39 chiral-catalysed 82 electro-. CO 84, 106, 191

formaldehyde. formic acid I06 H: 117 MeOH 88, 106, 146

ethers, a 87 glucose 106, 138 hydrocarbons, a 86

McOH, a 42.84 myrcene, (1 190 NH, 24 partial. CHI 24 [Pt"CL(Hzenda)]. a 84 thiophene, a 138 v o c s , a 138, 189 wet, phenol, a 138

40 reduction reaction, ORR, for Os,(CO),Nulcan C, a 88

42 sensors, a 137

Oxidation, alcohols

liquid organic waste 18 melt. Al-Mg-Pd, a 38

Oxygen, reaction with CO. u

on Pt/C, for fuel cells. a

Page

Phase Diagrams, Ag-Pd-Gd-Ru, a 38 Ir-Nb-Ni, Ir-Nb-Ni- Al 74 Pd-rare earth systems I08

Phase Transformation Kinetics, Pd-H, Pd-Er-H, Pd-W-H 169

Phenols, hydrogenation. N 86, 190 wet oxidation, a I38

Phenylation, aroyl chlorides, a 87 Phosphorescence, from Ir-based OLEDs. a I37

from Pd-poly@ara-phe@ylene) I87 Photocatalysis, in Pt(I1) quaterpyridine complex, a 39 Photoconversion, a 39.85, 137, 189

PGM Conference 165 Photoluminescence, see Luminescence Photoproperties, Pt-phenylene ethynylene

monomers, polymers. a I89 R~(phen)~(3-carbethoxy,4-hydro~y-phen)'+(PF~)~, a 1 89

85

Ru(I1) bipyridyls. dendrimeric oligomers 165 I37

[(PEt,)2HPt(~-Hz)Pt(PEt,)?][BPkll, Pt-Pt homolysis, a 85 [(PEt,),HPt(~-H)hH(PEtl)'][BPh,], Pt-h homolysis, a 85 [(PEt&PtH,]. [(PEt,),PtH(S)I[BP~], formation, a 85

39 39

Photosynthesis, Ru polypyridines, as models, a 85 Piperidines, from unsaturated N-chloroamines. a 139 "Platinum 2002" I I6

addition to, (NdEuGd)BaCuO, effects, a 42 capacitors 42.88, 107. 189

94 colloids 105, 136 drilling. by laser 72 electrodes, see Electrodes etching, using BCIJCI? gas plasma, a I40 films 107

laser welding, iewellery 66

Ru polypyridines, biomimetic assemblies, a ra~-[Ru(bpy)~(PhP(OMe)~(CI)]Cl. a 85

Photoreactions, Pd(I1) to Pd, by UV irradiation, a

Pt(I1) P-diketonates. with olefins. u R m i O z , COz reduction, by HI. a

Platinum, ACTTM, Power CoatingsTM 181

cathodic reactivity, in superdry conditions

in glass making 181 Palladium, AlMgPd ceramic composites, formation. a 38

94 circuit patterns, on polyimide, a I37 interaction with H2 37, 169

cathodic reactivity, in superdry conditions

ion source, a I36 nanoparticles, a 38, 84, 188, 190 Pd in poly@arcr-phenylene), phosphorescence 187 PdAg. nanocomposite, a 84 Pd-H. structural changes 169 Pd-rare earth systems. phase diagrams 108 Pd/n'-GaAs ohmic contacts, + Ge, Sn layers, a 88 [Pd,,;, M', MX], [Pd,-, M', ,(MX)I, ekctrogenerdted 94 solid solutions of H I69 thin films, a 85, 189

Palladium Alloys, Ag-Pd-Gd-Ru, a 38 Al-Mg-I'd, melt oxidaton, a 38 Al-Pd-Co. U-. V-phase, structures, a 38 dental, Ag-Au-I'd-Cu, a 88 interaction with HI 37, 169 membranes. a 86, 189 P&I,Cu3UPz,,Nilll, crystallisation, a I36 Pd41Ni,,Cu27Pzu melts, crystallisation, a 38 Pd-Er-H, Pd-W-H, structural changes 169 Pd-Pt, interaction with HI 3 1 Pd-rare earths 108 Pt-Pd. jewellery alloy 66 Ti(PdNi). shape memory, a 188

38 (C7H1 jNH)I[Pd(dmit),l. air-oxidation of, a 39 (C,HltNH)lPd(dmit),l, electrical conductivity, a 39 Pd(l1) N& macrocycles, synthesis, a 39 Pd(1I) with pincer-like amido ligand, (I 38 in poly@ara-phenylene), synthesis 187 [Pd"CI,J, formation, at C paste electrode, a 85

Palladium Compounds, Pd(NH3)dX. reduction, a 38 Na2(Pd2Cln), reduction. a 84

Patents 4347.89-91. 141-143, 192-194 pH, sensors, a 189

Palladium Complexes, (BQA)PdCI, preparation. a

melting point 66. 181 nanoparticles 38, 84, 88. 105. 106, 1 IS, 136 nanowires. a 136 ohmic contacts, WSi interlayerslp-type Sic, a 191 in 0 sensors, a 137 particles, electroless plated, on SPE membranes. a 40

39 [Pt2-, Na', Nal], reduction of 2.4-dinitrotoluene 94 Pt( I 1 I ), surface, for electrolyte hydration 106 [Pt,,-, M'. MXI, [Pt. , M+, ?(MX)!, electrogenerated 94 single crystals, for CO electrooxidation, a 84 thermal diffusivity 66 thin films, a 85, 88, 189 welding, laser 66

for solar cell electrodes, a

Platinum Alloys, CoCrPt film, perpendicular media. magnetic properties. a 191

CoCrPtB perpendicular media on TiZr, magnetic properties, a I40

electrodes, see Electrodes and Fuel Cells films, a I40

jewellery, Pt alloys 66 laser welding. jewellery 66 melting points 66. 181 nanoparticles 88, 106 Pt-Pd. interaction with Hz 37

thermal diffusivities 66 welding. laser 66

137

(~-C~H1)(Cl)Pt(~-CI),Ru(CI)(11':.rl'-2.7-dimethyl- octadienyl), nanocrystal precursor 14

(COD)PtCI, + dimethylphenyl(quinolinyl)amine, a 38 luminescence, a 39. 137

in glass making 181

Pt-Rh, coatings. ACTrM 181

Platinum Complexes, rrans-Pt(II), insulator, a (BQA)PtCI, preparation. a 38

Phtinum Metah h., 2002,46, (4) 203

Page PAGE

Ruthenium Alloys, (corn.)

Ruthenium Complexes, his(~'-2.4-diincthyl-

PI-Ru. jewellery alloy 66 Ta/Ru bufter layer, for CoCrPt perpendicular media, n 191

pentadienyl)Ru(II), for vapour-phase epitaxy, (I 42

Platinum Complexes, (cont. ) DhotODrODertieS. ( I 189

~hoto;ea~tions. LI 39.85 precursors for CVD, n 38. 107.189 LP~,CI~{N(H)C(BU')O)~], Pt(III)-Pt(llI) distance. ( I 136 lPt24(N(H)C(B~')o),l, o I36

Pt phthalocyanine, electrochemical doping of, a

Pt(I1) acetylacetonate, reaction with AI(CHI)J Pt(I1) N& macrocycles. synthesis. n

Pt octaethylporphyrin, in 0 sensor, a

[PtIvCl2(enda)l, by oxidation of [Pt"C1dH2enda)], a [Pt(en)iHzO)z]2', reaction with oL-penicillamine. a

I37 85 84 84

10s 39

Pt(I1) with pincer-like amido ligand, (I 38 Pt(II1) 'lantern-shaped'. u 136 PtR,(cod), ligand displacement reactions, n 136 PtR2L:. H20-soluble diorgano-, synthesis, (I 136 cis-. trcr,is-PtiYpy)2(NOl)l. aquation, hydrolysis, ci 188

88. 165. 166 [Rh,Pt,(CO)lb(dppm)~l, LRhxPt:(C0)21(dppm)?1, n 38

Platinum Compounds, antitumour agents electrodes, a K2[Pt(C,0,),], K2PtCIJ. K2PtC16. reduction, n thin films, u

geology conference

wastewater, electroflotation, (1 see also Emission Control

Polymerisation, co-, a fast living radical, N of phenylacetylene. (1

ROMP. a

matrix, for Pt complex thin film 0 sensor. ( I

polyimide, with Pd circuit patterns, n poly(/,aru-phenylene) + Pd. phosphorescence polystyrenes, hydrogenation. n Pt-phenylene ethynylenes, photoproperties, (I PVKPBD, with [Ir(DPF)& for OLEDs. n

Platinum Group Elements, geology book

Pollution Control, organic wastes, destruction

Polymers, coordination, Rh carboxylates, o

Power Coatings'", for the glass industry Propane, CO, reforming of. CI

Propene, for reduction of NOx Pyridines, chloro-, alkoxycarbonylation, n

dehydrogenation, a

Rare Earths, Pd-rare earths, eutectic phases

RCM, n Reactors, fixed bed catalyst, design aspects

solid solublities in Pd. strengthening effects

hydrogen-permeating membrane, a for liquid phase hatch hydrogenations

electron transfer. of 2,4-dinitrotoluene 0,. 0

Reduction, C02. by HI, CI

88 I36 88 17

I77 18

I37

139 I40

140, 190 87

188 I37 137 187 86

I89 I37 181 41 40

24.41 87

108 108

87. I40 144 189

48,92 39 94 42

Reforming, (I 41, 191

Rhodium Alloys, (Ir, Rh)7,Nbl,Nii,,. specific strength 74 Pr-Rh. coatings. ACT"' 181

Rhodium, Rhodium Bicentenary Competition 2

jewellery alloy 66 Rhodium Complexes, [ RhoPt(CO)lo(dppm)i].

[RhxPt,(CO),I(dppm)21. 38 Rh porphyrin alkyls. reactions with nitroxides, n 188 tetra(alkoxybenzoato)dirhodium(ll), liquid crystals, a I88

188 TpmsRh(LL) (LL = (CO)?, cod, nbd). Rh(I) chemistry, CI 84

Rhodium Compounds, SrCuRhOh, Sr,NiRhOh, LI 136 ROMP, n 87 Rosenmund Reduction, acid chlorides 73

effect of HIO 48 Russia, PGE geology. conference 177 Ruthenium, electrodes I06

Ru-doped InP. resistivities. a 42 Ru(001), surface, for electrolyte hydration 106

Ruthenium Alloys, Ag-Pd-Gd-Ru, a 38 electrodes, see Electrodes and Fuel Cells nanoparticles 88. 106

pyrazine adducts, liquid crystals, a

cance; drugs 165, 166 (~-C2HI)(CI)Pt(~-CI),Ru(Cl)(~' :~ '-2.7-dimethyl-

octadienyl ), nanocrystal precursor 14 luminescence 39. 85, 137. 165 (2-MelmH )?[ RuC11(2-Mclm ):I.

(2-MelniH).[RuC1~(2-Melm)]. synthesis. a 84 photoproperties 85, 165, 189 [RuCp(dppin)SR 1, micrnwave- ted synthesis, o 136 [RuH(arene)(Binap)lCF~SO!, piano-stool inverted. (I I88 [R~(L-L)~(cilatin)]~+, dimerisation. n I36

88. 105, 137. I88 LaSrCrRuO. SOFC anode material, ( I 191 RuO? powders, from RuCIl thermal decomposition, n 137

Selective Catalytic Reduction, + diesel particulate filter 27 NOx 27

Sensors, glucose. ( I 40. 86 H?, CI 189 hydrocarbons. CI 40 i n v i w biological 72 NO, ( r 40 0 2 , (I 137 pH, a 189

I88 41. 50, 138, 139. 140

84 85

RuOz. RuO?/Ti anodes, LI I37 39 50

I77 140 42 88

thin films. Pd-Ag. for Pd-ceramic membranes. (I 86 50

Sulfuric Acid, Ti/lr02-TaOi anodes, degradation. o I88

Supercapacitors, RuO-/C, nanoconiposite. ( I 88

Superconductors, Pt + CeO? additions, a 42 Suzuki Couplings, FibreCatT". Pd/C. n I90

Pd-polymer-bound phosphine. a 191

Ruthenium Compounds, electrodes

Shape Memory Effect, in Ti(PdNi). LI

Single Crystals, PI. CO electrooxidation, (I Sol-Gel, Pt-doped Sn02 th in films. a

Solar Cells, with Pt particles on wSi electrodes, a Sonogashira Couplings, of terminal alkynea

Silanes

South Africa, PGE geology, conference Sputtering, DC. films. Co-Pt. CI

thin films, Ir, IrO,. CI

reactive r.f. magnetron. thin films. PI-PtO,. n

Stille Couplings, aryl halides + organostannanes

Superalloys, Ir-based refractory 74

Ti2FeRu02. Ti,Fe,Ru-0,,, nanocrystalline I05

Suzuki-Miyaura Couplings 50

in superdry conditions 94 Tetraalkylammonium Salts, effects on Pd. Pt cathodes.

Tetralins, amino-, synthesis. n 191 Thermal Diffusivities, PI, PI alloys 66 Thin Films, Ir, IrO:. by DC sputtering. u 42

NilPd, XRD, LI 85 137 189 86

I89 I37 85 88

188

Pd, circuit patterns on polyimide. (1

Pd. for poly-Si wires. as H? sensors. n Pd-Ag. for ceramic composite membranes. n PI. by chemical vapour deposition, n Pt octaethylporphyrin. for 0 sensors. o Pt-doped SnO?. sol-gel preparation. ( I Pt-PtO,. for memory capacitor electrodes. a Ti(PdNi), bhape memory hehaviour. ti see also Films

Thinpenes, oxidation, n I38 Three-Way Catalysts 27.40 Tungsten, Pd-W-H. H effects on I69

Pt-W. jewellery alloy 66

VOCs, oxidation. ( I 138, 189 Voltammetry, (DNA-0s.bipy ). microanalysis. n 138

Water, waste, electrode system for electrollotation. u 137 Welding, laser. of PI jewellery 66

Pkztin#m Metalj Rm, 2002,46, (4) 204

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