Co-tolerant catalyst for PAFC
A binary alloy catalyst comprising platinum and tantalum, wherein the tantalum is present in the alloy at 15 to 50 atomic % and a phosphoric acid fuel cell comprising such a catalyst is disclosed. The catalyst provides a better CO tolerance.
1. A catalyst comprising a binary alloy comprising platinum and tantalum, wherein the tantalum is present in the binary alloy at 15 to 50 atomic % and a high surface area conductive carbon support material, wherein the binary alloy is dispersed on the support material at a loading of 5-15 wt % based on the weight of platinum versus the total weight of the catalyst.
2. An electrode comprising the catalyst according to claim 1 .
3. An electrode according to claim 2 , wherein the electrode is the anode.
4. A phosphoric acid fuel cell comprising an electrode according to claim 2 .
5. A phosphoric acid fuel cell comprising an anode according to claim 3 , a cathode and a phosphoric acid electrolyte disposed between the anode and cathode, and wherein the anode of the fuel cell, when in operation, is supplied with a carbon monoxide-containing hydrogen fuel.
6. A phosphoric acid fuel cell according to claim 5 , in which the electrolyte is liquid phosphoric acid held in a supporting matrix.
7. A phosphoric acid fuel cell according to claim 5 , in which the electrolyte is a phosphoric acid-doped polybenzimidazole membrane.
8. A process for operating a phosphoric acid fuel cell, the process comprising: providing a phosphoric acid fuel cell, comprising an anode, wherein the anode comprises a catalyst according to claim 1 ; providing a fuel stream to the anode wherein the fuel stream comprises carbon monoxide; and operating the fuel cell at elevated temperature.
9. The process according to claim 8 , wherein the fuel stream comprises up to 4% carbon monoxide.
10. The process according to claim 8 , wherein the fuel stream comprises at least 0.5% carbon monoxide.
11. The process according to claim 8 , wherein the fuel cell is operated at a temperature equal to or greater than about 120° C.
12. The catalyst according to claim 1 , wherein the high surface area conductive carbon support material is selected from the group consisting of oil furnace black, extra-conductive black, acetylene black, heat-treated acetylene black, graphitised acetylene black, carbon nanofibres and carbon nanotubes.