POLYMER COATING OF PEM FUEL CELL CATALYST LAYERS
A fuel cell ( 5 ) has catalysts ( 8, 9 ) on either side of a proton exchange membrane ( 7 ). The catalysts have a coating ( 19, 20 ) of soluble polymer and carbon forming microporous layers adhered to the catalyst chemically and/or by mechanical interference. The coating solution may be sprayed or rolled onto the catalyst or the catalyst may be dipped into the solution. Macroporous support layers ( 14, 15 ) may be adhered to the catalyst by the microporous coating.
1 . A fuel cell ( 5 ) comprising a proton exchange membrane ( 7 ), catalyst layers ( 8 , 9 ) having catalyst-supporting particles ( 25 ), said catalyst layers including a cathode catalyst layer on one surface of the membrane and an anode catalyst layer on a surface of the membrane opposite said one surface, a support layer ( 14 , 15 ) adjacent each catalyst layer;
characterized by:
a coating ( 19 , 20 ) of a mixture of soluble polymer ( 29 ) and fine carbon particles ( 26 ) and/or fine carbon fibers disposed only on an outward face ( 27 ) of at least one of said catalyst layers including surfaces of said catalyst supporting particles forming said outward face of said at least one of said catalyst layers.
2 . A fuel cell power plant ( 3 ) characterized by a fuel cell ( 5 ) according to claim 1 .
3 . A fuel cell ( 5 ) comprising a proton exchange membrane ( 7 ), catalyst layers ( 8 , 9 ) having catalyst-supporting particles ( 25 ), said catalyst layers including a cathode catalyst layer on one surface of the membrane and an anode catalyst layer on a surface of the membrane opposite said one surface;
characterized by:
a microporous layer ( 19 ) adhered to at least one of said catalyst layers either (a) chemically or (b) by mechanical interference.
4 . A fuel cell power plant ( 3 ) characterized by a fuel cell ( 5 ) according to claim 3 .
5 . A fuel cell ( 5 ) comprising:
a pair of catalyst layers ( 8 , 9 ) composed of catalyst ( 28 ) supported on carbon particles ( 25 ) with an ionically and electrically conductive binder;
a proton exchange membrane ( 7 ) disposed between said catalyst layers;
characterized by:
a coating ( 19 , 20 ) of a mixture of soluble polymer ( 29 ) and fine carbon particles ( 26 ) and/or fine carbon fibers disposed as a film adjacent an outward face ( 27 ) of at least one of said catalyst layers and contacting the surfaces of only the catalyst-supporting particles of said at least one of said catalyst layers which are about one or a few of the catalyst-supporting particles away from said outward face.
6 . A fuel cell ( 5 ) according to claim 5 characterized in that said at least one of said catalyst layers ( 8 , 9 ) is a cathode catalyst layer ( 9 ).
7 . A fuel cell ( 5 ) according to claim 5 further characterized in that said soluble polymer ( 29 ) in said coating ( 19 , 20 ) is selected from the list of: (a) amorphous perfluorinated hydrocarbon ethers, (b) copolymers and terpolymers of (i) tetrafluoro ethylene, (ii) hexafluoropropylene, (iii) 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole, (iv) pentafluoroethoxytrifluoroethene, and (v) trifluoromethoxytrifluoroethene and (c) copolymers of polyvinylidene fluoride with hexafluoro propylene.
8 . A fuel cell ( 5 ) according to claim 5 further characterized in that said mixture contains between 5 wt % and 99 wt % soluble polymer ( 29 ).
9 . A fuel cell ( 5 ) according to claim 5 further characterized by said coating ( 19 , 20 ) being no more than about 4 micrometers thick.
10 . A fuel cell ( 5 ) according to claim 5 further characterized by said coating ( 19 , 20 ) being no more than about 2 micrometers thick.
11 . A fuel cell power plant ( 3 ) characterized by a fuel cell ( 5 ) according to claim 5 .
12 . A method characterized by:
forming a suspension of soluble polymer ( 29 ), fine carbon particles ( 26 ) and/or fine carbon fibers and a volatile solvent;
coating only the outward face ( 27 ) of at least one catalyst layer ( 8 , 9 ), of a proton exchange membrane fuel cell ( 5 ), with said suspension; and
allowing said suspension to dry.
13 . A method according to claim 12 further characterized in that said step of coating comprises coating only the outward face ( 27 ) of two catalyst layers ( 8 , 9 ) of said proton exchange membrane fuel cell ( 5 ).
14 . A fuel cell ( 5 ) characterized by being formed by a process including the method of claim 12 .
15 . A fuel cell power plant ( 3 ) characterized by a fuel cell ( 5 ) according to claim 14 .
16 . A fuel cell ( 5 ) comprising a proton exchange membrane ( 7 ), catalyst layers ( 8 , 9 ) having catalyst-supporting particles ( 25 ), said catalyst layers including a cathode catalyst layer on one surface of the membrane and an anode catalyst layer on a surface of the membrane opposite said one surface, a support layer ( 14 , 15 ) adjacent each catalyst layer;
characterized by:
at least one of said support layers adhered to at least one of said catalyst layers either (a) chemically or (b) by mechanical interference.
17 . A fuel cell power plant ( 3 ) characterized by a fuel cell ( 5 ) according to claim 16 .
18 . A fuel cell ( 5 ) characterized by:
a microporous layer ( 19 , 20 ) adjacent an outer surface of a catalyst layer ( 8 , 9 ), said microporous layer not more than two micrometers thick, formed of a mixture of soluble polymer ( 29 ) and fine carbon particles ( 26 ) and/or fine carbon fibers.
19 . A fuel cell power plant ( 3 ) characterized by a fuel cell ( 5 ) according to claim 18 .
20 . A fuel cell ( 5 ) comprising a proton exchange membrane ( 7 ), catalyst layers ( 8 , 9 ) having catalyst-supporting particles ( 25 ), said catalyst layers including a cathode catalyst layer on one surface of the membrane and an anode catalyst layer on a surface of the membrane opposite said one surface, a support layer ( 14 , 15 ) adjacent each catalyst layer;
characterized by:
a microporous layer ( 19 , 20 ) not more than two micrometers thick between at least one of said support layers ( 14 , 15 ) and the catalyst layer ( 8 , 9 ) adjacent thereto.