Gas diffusion substrate and electrode
An electrically conducting gas diffusion substrate, capable of removing oxidizable impurities from an impure gas stream, which comprises an electrically conducting porous structure and a first catalytic component, wherein the first catalytic component comprises a first catalyst supported on an electrically non-conducting support is disclosed. In addition, an electrode, a membrane electrode assembly and a fuel cell each comprising said electrically conducting gas diffusion substrate is disclosed.
1. A gas diffusion electrode comprising:
(i) an electrically conducting porous structure;
(ii) a first catalytic component, said first catalytic component being embedded within the porous structure and being a gas-phase catalyst designed to remove contaminant gases, wherein said first catalytic component comprises a first catalyst which is one or more noble metals or non-noble metals or a combination thereof, and wherein said first catalyst is directly supported on an electrically non-conducting support; and
(iii) a second catalytic component, said second catalytic component being applied to the porous structure as a surface layer and being an electrocatalyst adapted to facilitate an electrochemical reaction, wherein said second catalytic component comprises a second catalyst which is a precious metal or a transition metal as a metal or a metal oxide, either unsupported or supported in a dispersed form on a carbon support; an organic complex, in the form of a high surface area finely divided powder or fibre; or a combination thereof.
2. A gas diffusion electrode according to claim 1 , wherein the first catalyst is selected from the group consisting of platinum, palladium, ruthenium, rhodium, gold, chromium, molybdenum, nickel and manganese or a combination thereof.
3. A gas diffusion electrode according to claim 1 , wherein the electrically non-conducting support is an oxidic support.
4. A gas diffusion electrode according to claim 1 , wherein the electrically non-conducting support is selected from the group consisting of alumina, silica, ceria, zirconia, an oxide of iron, a manganese oxide and titania.
5. A gas diffusion electrode according to claim 1 , wherein the second catalytic component is a platinum/ruthenium alloy supported on carbon black or platinum supported on carbon black.
6. A gas diffusion electrode according to claim 1 , wherein the porous structure is a woven or non-woven fibrous material.
7. A gas diffusion electrode according to claim 1 , wherein the porous structure is a woven or non-woven fibrous material and further comprises a filler material.
8. A gas diffusion electrode according to claim 1 , wherein the porous structure is formed from a polymer.
9. A gas diffusion electrode according to claim 1 , wherein the porous structure is a metal mesh.
10. A membrane electrode assembly comprising a gas diffusion electrode as claimed in claim 1 , a second gas diffusion electrode, and a solid polymer membrane.
11. A fuel cell comprising a membrane electrode assembly as claimed in claim 10 .
12. A membrane electrode assembly comprising a gas diffusion electrode as claimed in claim 1 , a gas diffusion substrate and a solid polymer membrane, wherein an electrocatalyst layer is applied to the side of the membrane facing the gas diffusion substrate.
13. A fuel cell comprising a membrane electrode assembly as claimed in claim 12 .
14. A fuel cell comprising a gas diffusion electrode as claimed in claim 1 .