Catalyst layer
A porous catalyst layer formed from discrete particles of unsupported metal, wherein at least 80%, suitably at least 90%, of the discrete particles have a mass of from 1 to 1000 zeptograms, and wherein the catalyst layer has a metal volume fraction of less than 30% and a metal loading of less than 0.09 mg/cm 2 is disclosed. The catalyst layer is suitable for use in fuel cells and other electrochemical applications.
1. A porous catalyst layer formed from discrete particles of unsupported metal, wherein at least 80% of the discrete partcles have a mass of from 1 to 1000 zeptograms, and wherein the catalyst layer has a metal volume fraction of less than 30% and a metal loading of from 0.001 mg/cm 2 to 0.09 mg/cm 2 .
2. A porous catalyst layer according to claim 1 , wherein at least 80% of the discrete particles have a mass of from 1 to 200 zeptograms.
3. A porous catalyst layer according to claim 1 , wherein the metal is selected from the group consisting of platinum, ruthenium, palladium, rhodium, iridium, osmium, gold, silver, base metal, and oxides, alloys and mixtures thereof.
4. A porous catalyst layer according to claim 3 , wherein the metal is platinum.
5. A porous catalyst layer according to claim 1 , wherein the catalyst layer further comprises one or more polymers.
6. A porous catalyst layer according to claim 5 , wherein the polymer is an ionomer.
7. A porous catalyst layer according to claim 5 , wherein the polymer is a hydrophobic polymer.
8. A gas diffusion electrode comprising a porous catalyst layer as claimed in claim 1 .
9. A fuel cell comprising an electrode as claimed in claim 8 .
10. A catalyst coated membrane comprising a porous catalyst layer as claimed in claim 1 .
11. A catalyst coated membrane according to claim 10 , wherein metal particles from the catalyst layer are embedded within the membrane.
12. A transfer substrate comprising a porous catalyst layer as claimed in claim 1 .
13. A membrane electrode assembly comprising a catalyst layer as claimed in claim 1 .
14. A fuel cell comprising a membrane electrode assembly as claimed in claim 13 .