Fuel cell membranes and catalytic layers
View Patent ↗To form an ionomer-based catalytic layer on a porous substrate, a heat source ( 40 ) is used to dry an ionomer-containing spray ( 46 ) so that it does not substantially liquid flow on the substrate ( 14 ). The ionomer spray ( 46 ) may contain a catalyst. A spray ( 46 ) of mixed material for forming the catalytic layer is entrained by a gas stream and is heated and directed to a substrate surface ( 12 ). For hydrogen/oxygen fuel cells, catalytic material is incorporated into the proton-conducting membrane ( 56 ) to convert diffusing oxygen and hydrogen to water to reduce potential loss at the electrodes and maintain hydration of the proton-conducting membrane ( 56 ).
1. A method for depositing a catalytic layer on a surface of a substrate, the method comprising
providing a continuous fluid streams that flows from upstream to downstream to impinge on said substrate,
introducing particulates of support material into said fluid stream and, at a first upstream region of said fluid stream, depositing catalytic material on said support material particulates to produce particulates of supported catalytic material,
in a second region of said fluid stream downstream of said first region, providing a spray comprising polymeric material so as to mix said polymeric material and said supported catalytic material, and
impinging said fluid stream on said substrate surface so as to co-deposit said supported catalytic material particulates and said polymeric material on said substrate surface.
2. The method of claim 1 wherein said first region is at an elevated first temperature and said second region is at a second temperature lower than said first region.
3. The method of claim 2 wherein said catalytic material is produced in said first region by thermal reaction of material that is precursor to said catalytic material.
4. The method of claim 3 wherein said thermal reaction occurs in a flame.
5. The method of claim 1 wherein a quenching fluid is introduced into said gas stream downstream of said first region.
6. Apparatus for co-depositing catalytic material and polymeric material on a substrate, said apparatus comprising
gas flow means for directing a stream of gas through a first upstream region, a second region downstream of said first region, and a deposition region downstream of said second region,
means for locating a substrate in said deposition region such that the stream of gas impinges on said substrate,
means for introducing particulates of support material into said fluid stream at or upstream of said first upstream region,
means at said first upstream region for depositing catalytic material on said support material particulates to produce particulates of supported catalytic material,
at said second region, means for providing a spray of polymeric material so as to mix said polymeric material and said supported catalytic material, and
means to impinge said fluid stream on said substrate surface so as to co-deposit said supported catalytic material particulates and said polymeric material on said substrate surface.
7. Apparatus according to claim 6 wherein said deposition means at said first location comprises means to introduce a precursor of said catalytic material and means to heat said precursor to produce said catalytic material by thermal reaction.
8. Apparatus according to claim 6 wherein said heating means is a flame.
9. Apparatus according to claim 6 including quenching means to lower the temperature from said first region to said second region.
10. Apparatus according to claim 9 wherein said quenching means comprises means to introduce cooling fluid into said gas stream downstream of said first region.