Direct oxidation fuel cells with improved cathode gas diffusion media for low air stoichiometry operation
AssigneePanasonic Corporation
InventorsGuoqiang Lu, Chao-Yang Wang, Takashi Akiyama
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Abstract
A cathode for use in a direct oxidation fuel cell (DOFC) comprises a gas diffusion medium (GDM) including a backing layer and a microporous layer comprising a fluoropolymer and an electrically conductive material, wherein loading of the fluoropolymer in the microporous layer is in the range from about 10 to about 60 wt. %. In use, a concentrated solution of a liquid fuel is supplied to an anode and an oxidant to the cathode of the fuel cell, and the fuel cell may be operated at a low oxidant stoichiometry ξc not greater than about 2.5.
Claims13
A method of operating a direct oxidation fuel cell (DOFC) system, wherein the system comprises:
- (i) at least one membrane electrode assembly which includes a cathode, an anode and an electrolyte positioned therebetween, said cathode comprises, in direct overlying sequence, a catalyst layer, a microporous layer and a gas diffusion medium (GDM), wherein said microporous layer comprises an electrically conductive material and a fluoropolymer which is in a range about 10 wt. % to about 60 wt. %, wherein said microporous layer has a thickness ranging from about 10 to about 50 μm and an average pore size between about 10 and about 500 nm, and said GDM comprises a backing layer, and (ii) a liquid/gas separator, the method comprising:
- supplying a concentrated solution of a liquid fuel to said anode and an oxidant to said cathode which produces water, wherein some of the produced water is transported to the liquid/gas separator and subsequently supplied to the anode;
- and
- operating said at least one membrane electrode assembly at a low oxidant stoichiometry ξc not greater than about 4;
- wherein
- ξ
- c
- =
- 0.42
-
- (
- γ
- +
- 2
- )
- 3
-
-
- η
- fuel
-
- p
- p
- sat
- and ξc is the oxidant stoichiometry, γ is the ratio of water to fuel in the fuel supply, psat is the water vapor saturation pressure corresponding to the cell temperature, p is the cathode operating pressure, and ηfuel is the fuel efficiency.
A method of operating a direct oxidation fuel cell (DOFC) system, wherein the system comprises at least one membrane electrode assembly which includes a cathode, an anode and an electrolyte positioned therebetween, said cathode comprises, in direct overlying sequence, a catalyst layer, a microporous layer and a gas diffusion medium (GDM), said microporous layer comprises an electrically conductive material loaded in an amount from about 0.5 to about 5 mg/cm2 and (b) a fluoropolymer loaded in a range from about 10 wt. % to about 60 wt. %, in the microporous layer, wherein said microporous layer has a thickness ranging from about 10 to about 50 μm and an average pore size between about 10 and about 500 nm, said GDM comprises a backing layer which includes carbon paper or woven or non-woven cloth having a porosity greater than about 70%, the method comprising:
- supplying a concentrated solution of a liquid fuel to said anode and an oxidant to said cathode;
- and
- operating said at least one membrane electrode assembly at a low oxidant stoichiometry ξc not greater than about 8;
- wherein
- ξ
- c
- =
- 0.42
-
- (
- γ
- +
- 2
- )
- 3
-
-
- η
- fuel
-
- p
- p
- sat
- and ξc is the oxidant stoichiometry, γ is the ratio of water to fuel in the fuel supply, psat is the water vapor saturation pressure corresponding to the cell temperature, p is the cathode operating pressure, and ηfuel is the fuel efficiency.
Dependencies are inferred from the claim text.