DURABLE FUEL CELL WITH PLATINUM COBALT ALLOY CATHODE CATALYST AND SELECTIVELY CONDUCTING ANODE
The degradation associated with repeated startup and shutdown of solid polymer electrolyte fuel cells comprising PtCo alloy cathode catalysts can be particularly poor. However, a marked and unexpected improvement in durability is observed as a result of incorporating a selectively conducting component in electrical series with the anode components in the fuel cell.
1 . A solid polymer electrolyte fuel cell comprising a solid polymer electrolyte, a cathode, and anode components connected in series electrically wherein:
i) the anode components comprise an anode and a selectively conducting component;
ii) the selectively conducting component comprises a selectively conducting material; and
iii) the electrical resistance of the selectively conducting component in the presence of hydrogen is more than 100 times lower than the electrical resistance in the presence of air; and
the cathode comprises a PtCo alloy catalyst.
2 . The fuel cell of claim 1 wherein the cathode comprises a carbon supported PtCo alloy catalyst.
3 . The fuel cell of claim 2 wherein the carbon supported PtCo alloy catalyst comprises 25-30%, preferably 27-29%, most preferably 27.5-28.5% Pt and 2-6%, preferably 3-5, most preferably 3.5-4.5% Co by weight.
4 . The fuel cell of claim 1 wherein the electrical resistance of the selectively conducting component in the presence of hydrogen is more than 1000 times lower than the electrical resistance in the presence of air.
5 . The fuel cell of claim 1 wherein the selectively conducting material is tin oxide.
6 . The fuel cell of claim 5 wherein the selectively conducting material additionally comprises platinum deposited on the tin oxide.
7 . The fuel cell of claim 6 wherein the selectively conducting material comprises 0.5 to 2%, preferably 0.75 to 1.5, most preferably about 1% by weight of platinum deposited on the tin oxide.
8 . The fuel cell of claim 1 wherein the anode components comprise an anode gas diffusion layer adjacent the anode, the selectively conducting component is the anode gas diffusion layer, and the selectively conducting material is incorporated as a layer on the side of the anode gas diffusion layer adjacent the anode.
9 . The fuel cell of claim 8 wherein the layer of selectively conducting material is from about 15 to about 20 micrometers thick.
10 . A method for reducing degradation of a solid polymer electrolyte fuel cell comprising a solid polymer electrolyte, a cathode comprising a PtCo alloy catalyst, and anode components comprising an anode, the method comprising:
incorporating a selectively conducting component in electrical series with the anode components wherein the selectively conducting component comprises a selectively conducting material, and the electrical resistance of the selectively conducting component in the presence of hydrogen is more than 100 times lower than the electrical resistance in the presence of air.
11 . The method of claim 10 wherein the cathode comprises a carbon supported PtCo alloy catalyst.
12 . The method of claim 10 wherein the selectively conducting material is tin oxide.
13 . The method of claim 12 wherein the selectively conducting material comprises 0.5 to 2%, preferably 0.75 to 1.5, most preferably about 1% by weight of platinum deposited on the tin oxide.
14 . The method of claim 10 wherein the anode components comprise an anode gas diffusion layer adjacent the anode, the method comprising incorporating the selectively conducting material as a layer on the side of the anode gas diffusion layer adjacent the anode.
15 . A vehicle comprising a traction power supply comprising the fuel cell of claim 1 .