Catalyst
An electrocatalyst, suitable for use in a fuel cell, comprises an alloy having a single crystalline phase, wherein the alloy consists of 5-95 at % palladium, 5-95 at % ruthenium and less than 10 at % of other metals, provided that the alloy does not consist of 50 at % palladium and 50 at % ruthenium.
1. An electrocatalyst comprising an alloy having a single crystalline phase, wherein the alloy consists of 5-95 at % palladium, 5-95 at % ruthenium and, optionally, platinum having less than 10 at % platinum, provided that the alloy does not consist of 50 at % palladium and 50 at % ruthenium.
2. An electrocatalyst according to claim 1 , wherein the amount of palladium in the alloy is at least 20 at %.
3. An electrocatalyst according to claim 1 , wherein the amount of ruthenium in the alloy is at least 20 at %.
4. An electrocatalyst according to claim 1 , wherein the amount of platinum in the alloy is up to 5 at %.
5. An electrocatalyst according to claim 1 , wherein the amount of palladium in the alloy is from 5 to 49 at %, the amount of ruthenium in the alloy is from 51 to 95 at %, and the amount of platinum is up to 10 at %.
6. An electrocatalyst according to claim 1 , wherein when the amount of palladium in the alloy is less than 30 at %, the amount of platinum in the alloy is greater than 0 at %.
7. An electrocatalyst according to claim 1 , wherein the electrocatalyst consists of the alloy.
8. An electrocatalyst according to claim 1 , wherein the electrocatalyst comprises the alloy supported on a high surface area support material.
9. A method for preparing an electrocatalyst according to claim 1 comprising the steps of:
(a) preparing a solution comprising a palladium salt, a ruthenium salt and optionally a salts of platinum;
(b) co-precipitating the metals, optionally in the presence of a high-surface area support material, by adjusting the pH;
(c) filtering;
(d) drying; and
(e) firing in a reducing atmosphere.
10. A method for preparing an electrocatalyst according to claim 9 , wherein the co-precipitating step occurs in the presence of a high surface area support material.
11. A catalyst ink comprising an electrocatalyst according to claim 1 dispersed in a solvent and further comprising a proton-conducting polymer.
12. A catalysed gas diffusion electrode comprising a gas diffusion material and an electrocatalyst layer deposited on the gas diffusion material, wherein the electrocatalyst layer comprises an electrocatalyst according to claim 1 .
13. A catalysed membrane comprising a proton exchange membrane and an electrocatalyst layer deposited on the membrane, wherein the electrocatalyst layer comprises an electrocatalyst according to claim 1 .
14. A membrane electrode assembly comprising an electrocatalyst according to claim 1 .
15. A fuel cell wherein the anode comprises an electrocatalyst according to claim 1 .
16. A direct methanol fuel cell wherein the anode comprises an electrocatalyst according to claim 1 .