Gas diffusion substrate and electrode
An electrically conducting gas diffusion substrate, capable of removing oxidisable 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 process for the preparation of a gas diffusion substrate, wherein said substrate comprises (i) an electrically conducting porous structure, and (ii) a first catalytic component, said process comprising in-filling a pre-formed electrically conducting porous structure with the first catalytic component to embed the first catalytic component within the electrically conducting porous structure, wherein the first catalytic component (1) is a gas-phase catalyst designed to remove contaminant gases, and (2) 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.
2. A process 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 process according to claim 1 , wherein the electrically non-conducting support is an oxidic support.
4. A process 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 process according to claim 1 , wherein the electrically conducting porous structure is a woven fibrous material or a non-woven fibrous material.
6. A process according to claim 5 , wherein the electrically conducting porous structure further comprises a filler material.
7. A process according to claim 1 , wherein the electrically conducting porous structure is formed from a polymer.
8. A process according to claim 1 , wherein the electrically conducting porous structure is a metal mesh.
9. A process for the preparation of a gas diffusion electrode, wherein said electrode comprises (i) an electrically conducting porous structure, (ii) a first catalytic component, and (iii) a second catalytic component, said process comprising: (1) in-filling a pre-formed porous structure with the first catalytic component to embed the first catalytic component within the electrically conducting porous structure and (2) applying the second catalytic component to the electrically conducting porous structure as a surface layer;
wherein the first catalytic component (1) is a gas-phase catalyst designed to remove contaminant gases, and (2) 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
wherein the second catalytic component (1) is an electrocatalyst adapted to facilitate an electrochemical reaction, and (2) comprises a second catalyst which is a precious metal or a transition metal as a metal or a metal oxide, and wherein the second catalyst is 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.
10. A process according to claim 9 , wherein the second catalytic component is a platinum/ruthenium alloy supported on carbon black.
11. A process according to claim 9 , wherein the second catalytic component is platinum supported on carbon black.