High utilization supported catalytic metal-containing gas-diffusion electrode, process for making it, and cells utilizing it

Abstract

Gas-diffusion electrodes (GDE's) suitable for use with a solid polymer electrolyte (s.p.e.), particularly in s.p.e. fuel cells, which GDE's provide unusually highly efficient use of noble or precious electrocatalytic metals, are obtained by starting with a GDE which is essentially fully fabricated except for electrocatalytic metal treatment and s.p.e. treatment, e.g. a carbon GDE having a gas-permeable hydrophobic face and a particulate carbon-containing catalytic face. This untreated GDE is treated by a. impregnating an s.p.e. solutuion into the catalytic face until the solution penetrates part way into the cross-section of the GDE, especially into the carbon particulate or other support material, but not as far as the hydrophobic, gas permeable face, b. inserting the thus-treated GDE and a counterelectrode into a plating bath containing, for example, M.sup.+, M.sup.++, and/or M.sup.+++ ions, where M is a metal of Group VIII or I-B of the Periodic Table, and c. applying an interrupted current (periodically interrupted or a single, long pulse <2 minutes in duration) to the thus-treated GDE, so that metal particles<10 nm (<100A) in average particle size deposit on the particulate support material (e.g. high surface are carbon) of the catalytic face, but essentially only on sites where the support material is already in contact with the previously-deposited s.p.e. Because the deposited metal particles are in contact with an ionic pathway (through the s.p.e.) and an electronic pathway (through the support material), virtually every deposited metal particle is effective in catalyzing the electro-oxidation or electro-reduction of a reactant gas supplied to the gas-permeable hydrophobic face of the GDE during cell operation. s.p.e. fuel cells of this invention provide good performance with GDE loadings of 0.05-4.0 mg/cm.sup.2 of catalytic metal, a performance comparable to cells with GDE loadings of about 0.5 mg/cm.sup.2 of the same metal.

Dependencies are inferred from the claim text.