Method of operating a fuel cell
First Claim
1. A method of operating a fuel cell of the type comprising an anode and a cathode each comprising catalyst means comprising platinum, the method comprising supplying gaseous fuel comprising hydrogen and/or a gaseous alcohol to said anode and supplying gaseous oxidant comprising oxygen to said cathode, operating the fuel cell at a temperature which does not exceed substantially 250°
- C., providing an interruptable first circuit externally of the cell for electric current derived from the cell to flow in the external circuit from the cathode to the anode by reason of the cathode being at a positive potential relative to the anode, providing a second circuit externally of the cell, said second circuit comprising electrical energy supply means for supplying selectively a reverse D.C. potential to said anode and cathode thereby putting the anode at a positive potential with respect to said cathode, interrupting and completing the first circuit alternately and operating the second circuit whereby when the first circuit is interrupted the reverse D.C. potential is applied simultaneously by means of the second circuit and when the first circuit is completed application of said reverse D.C. potential ceases, said first circuit being completed for a first time period and said reverse D.C. potential being applied for a second time period, said first time period being at least substantially ten times greater than said second time period, and the second time period being not greater than substantially 0.25 seconds.
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Accused Products
Abstract
A fuel cell is operated at a temperature which is not greater than substantially 250° C., has an electrolyte which can be a solid polymer electrolyte, a liquid phosphoric acid electrolyte, or a liquid alkaline electrolyte, and a cathode and an anode each comprising a platinum catalyst. Hydrogen fuel gas is supplied to the anode and a gaseous oxidant, for example oxygen is supplied to the cathode. The cathode and anode are both connected to first and second circuits in parallel. The first circuit includes a load to be powered by the fuel cell and a first switch. The second circuit includes a battery and a second switch. The switches are operated by a control. When the first swtich is closed the cell powers the load and the second switch is open. When the first switch is open the second switch is closed so the battery applies a reverse D.C. potential the anode and cathode. The first switch is closed and the second switch is open for a time period T1 which is substantially at least ten times greater than time period T2 for which the first switch is open and the second switch is closed. The time period T2 does not exceed substantially 0.25 seconds. The switches can be relays or solid state electronic switch arrangements.
66 Citations
28 Claims
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1. A method of operating a fuel cell of the type comprising an anode and a cathode each comprising catalyst means comprising platinum, the method comprising supplying gaseous fuel comprising hydrogen and/or a gaseous alcohol to said anode and supplying gaseous oxidant comprising oxygen to said cathode, operating the fuel cell at a temperature which does not exceed substantially 250°
- C., providing an interruptable first circuit externally of the cell for electric current derived from the cell to flow in the external circuit from the cathode to the anode by reason of the cathode being at a positive potential relative to the anode, providing a second circuit externally of the cell, said second circuit comprising electrical energy supply means for supplying selectively a reverse D.C. potential to said anode and cathode thereby putting the anode at a positive potential with respect to said cathode, interrupting and completing the first circuit alternately and operating the second circuit whereby when the first circuit is interrupted the reverse D.C. potential is applied simultaneously by means of the second circuit and when the first circuit is completed application of said reverse D.C. potential ceases, said first circuit being completed for a first time period and said reverse D.C. potential being applied for a second time period, said first time period being at least substantially ten times greater than said second time period, and the second time period being not greater than substantially 0.25 seconds.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
Specification