Dr. Paramaconi Rodriguez

Cutting edge method for the preparation of catalyst for PEFC, AFC and DAFC

H2FC Supergen Dec 2013

Group of

Advanced

Materials and

Electrochemistry

Surfactant

+ +

+ =

NaX Graphite (CE) Pt (WE)

Battery

A very simple experiment (water electrolysis)

Cathodic treatment of a Pt wire: 1 minute at -10V in 10M NaOH

99.99% Pt

0.1mm

Pt -10V / 5min

NaOH

Cyclic voltammogram of Pt in 0.5M H2SO4

Surface area

increase x17

0

-5

AC generator

A

Characterization of cathodic nanoparticles

TEM

EDX

XRD

0

20

40

60

80

100

120

140

160

180

200

0-2 2-4 4-6 6-8 8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24 More

nm

Size distribution

The mechanism….!

0 5 10 15 20 25 301.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6 1M LiOH

1M NaOH

1M CsOH

1M t-Bu4NOH

10M NaOH

1M Na2SO4

1M NaCl

1M NaClO4

1M NaCl + 1M NaOH

1M NaClO4 + 1M NaOH

1M NaClO4 + 1M HClO4

1M NH4ClO4 + 1M HClO4

molten NaOH

log

(e

tch

ing

tim

e / s

eco

nd

s)

AC Amplitude / V

A.I. Yanson et al. Angew. Chem. Int. Ed, 50, 2011, 6346-6350.

Some cases the nanoparticles appear as oxides

Chemical oxidation in the solution

A.I. Yanson et al. Angew. Chem. Int. Ed, 50, 2011, 6346-6350.

Catalytic activity of cathodic platinum nanoparticles

Black – commercial (TKK) 5 nm Red – cathodic platinum 8-10 nm

Hydrogen adsorption

CO monolayer oxidation

Methanol oxidation

110mV

DOE 2017 target

Cathode loading: 0.125mg/cm2

Cost of Pt in a 50 cm2 cathode by reduction of PtCl4 salt: £50

Cost of Pt in a 50 cm2 cathode by cathodic corrosion: £15,08

Size control of “cathodic” nanoparticles

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

6

7

8

9

10

11

12

13

N

P s

ize b

y 1

st X

RD

peak (

nm

)

"rms" ac current (A)

Pt NP prepared in 5M NaOH

0.0

5.0x10-3

1.0x10-2

1.5x10-2

Effic

iency (

s-1)

Alloys?

… what if the starting wire is an alloy?

EDX analysis of nanoparticles

… then we get alloyed nanoparticles!

Electro-oxidation performance of PtRh NPs

Pt

Pt90Rh10

Pt70Rh30

Pt20Rh80

Rh

Blank CV

Methanol oxidation

P. Rodriguez, et al.J. Am. Chem. Soc., 2011, 133 (44), 17626–17629.

CO

Methanol

Pt Pt95Ru5

P. Rodriguez, et al.J. Am. Chem. Soc., 2011, 133 (44), 17626–17629.

Catalytic activity towards FC reactions

Metal

Size

Alloy

Shape (surface orientation)

Parameters that influence catalysis

Preferential oriented nanoparticles

Cu

M.Duca et al. Topics in Catalysis 2013 DOI: 10.1007/s11244-013-0180-5

Problems with the degradation of the carbon support in the Fuel cell?

Schulenburg, H. et al. Journal of Physical Chemistry C 2011, 115, 14236.

TiO2

Au@TiO2

Pt@TiO2

Cathodic Corrosion as a potential method to

prepare clean High Surface Area Electrode Catalyst

and nanoparticles

Control over the composition, size, orientation

Prof. Marc T.M Koper

Dr. Alex Yanson

Dr. Nuria Garcia

Dr. Matteo Duca

Rik Mom

Rico Wanders

Pavel Antonov

Dr. Paramaconi Rodriguez

Cutting edge method for the preparation of catalyst for PEFC, AFC and DAFC

p.b.rodriguez@bham.ac.uk

1PhD position available

Advances in Materials Science, Processing, and Engineering for

Fuel Cells and Electrolyzers

Dario Marrocchelli (Massachusetts Institute of Technology), Giuliano Gregori (Max-

Planck-Institut für Festkörperforschung), Enrico Traversa (KAUST), Daniele Pergolesi

(Paul Scherrer Institut), Monica Burriel (Imperial College), Kazunari Sasaki (Kyushu

University) Lin Zhuang (Wuhan University), Olaf Conrad (University of Cape Town),

Yang Shao-Horn (Massachusetts Institute of Technology), Hong Yang (University of

Illinois), Hubert Girault (EPFL), Jan Rossmeisl (Technical University of Denmark),

Venkat Viswanathan (Massachusetts Institute of Technology),.

November 30 - December 5, 2014

Boston, Massachusetts

Supporting info

• In 1907 experiments in liquid ammonia by Kraus produced species of Na+ and

Pb2-

• In the 1930’s Zintl deduced the existence of Na4Pb9,

or a “Zintl ion” Pb94-. Also detected anion Au-

• By the end of 1940’s anions of Hg-, Au- and Li-

were identified in gas phase by mass-spec

• In the 1950’s the first solid ionic compounds of the

type Cs+Au- were synthesized in vacuum

• In 1980’s unambiguous evidence appeared for the existence

of monatomic metal anions in solution and the solid state

• In 2003 a Cs2Pt solid containing Pt2- anion was obtained

Onset potential for Pt is less negative than -2V !

Ge94- Cs4Ge9

Experimental setup

Alloying of a cathode metal with an alkali, and subsequent

leaching of the alloy is inconsistent with the following observation:

• Crystallographic etch pits are indicative of chemical dissolution

short (above) and long (below) cathodic treatments

Haber’s mechanism: alloying with alkali and subsequent leaching

History of metal anions

• In 1907 experiments in liquid ammonia by Kraus produced species

of Na+ and Pb2-

In the 1930’s Zintl concluded that that was Na4Pb9, or a “Zintl ion”

Pb94-. Also detected anion Au-

By the end of 1940’s anions of Hg-, Au- and Li- were identified in gas

phase by mass-spectroscopy

In the 1950’s the first solid ionic compounds of the type Cs+Au- were

synthesized in vacuum

Not before the 1980’s did the world have unambiguous evidence for

the existence of monatomic metal anions in solution and the solid state

In 2003 a Cs2Pt solid containing Pt2- dianion was obtained

… they exist, but are hard to find and handle

(intolerant to air, water, anything reducible) History of metal anions

Low-temperature STM of Au on NaCl: switching Au J. Repp, G. Meyer, F.E. Olsson, and M. Persson, Science 305, 493 (2004)

Annealed gold wire cathodically treated at -10 Vdc in an

electrolyte containing 1M Na+ ions. Left image shows a clear

crystal grain boundary and different corrosion rates on different

crystal orientations. Right image is a zoom-in, showing how

within 1 micron of the grain boundary the surface concentration

of nanoparticles clearly changes. The latter is an indication of the

very limited diffusion of nanoparticle-forming species (metal

anions), corroborating our hypothesis of an extremely thin aprotic

layer and very short lifetimes of metal anions.

Supporting info

0 2 4 6 8 10 12 14200

300

400

500

600

Tim

e / s

pH

Time required to atomize 0.12 mm dia. Pt wire submerged

by 1mm in 0.5M NaOH + x HClO4 solution. 20 V p-p

square wave, 100 Hz. Weak (if any) dependence is

indicative of the fact that under extreme cathodic (anodic)

potentials the pH in the vicinity of the electrode is

strongly shifted towards high (low) pH values due to the

consumption of protons (hydroxyl ions).

Supporting info