Gas diffusion electrode for membrane fuel cells and method of its production
AssigneeDegussa AG
InventorsAndreas Fischer, Hartmut Wendt, Ralf Zuber
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Abstract
A porous gas diffusion electrode for membrane fuel cells on an ion-conducting polymer. The electrode contains a finely divided electrocatalyst which is dispersed in a proton-conducting ionomer and has a total porosity of more than 40 to less than 75%. It supplies considerably improved performance data in comparison to known electrodes. The electrode can be produced by using pore-forming materials which are dissolved during the re-protonation of the ion-conducting polymers with sulfuric acid or are decomposed by the action of temperature.
Claims26
A gas diffusion electrode for use in membrane fuel cells consisting essentially of a proton-conducting polymer having dispersed therein a finely divided electrocatalyst, said electrode having a total porosity in a range more than 40 to less than 75% by volume.
A fuel cell comprising a membrane and gas diffusion electrode wherein said electrode consists essentially of a proton-conducting polymer containing a finely divided electrocatalyst dispersed in said proton-conducting polymer, said electrode composition having a total porosity in a range more than 40 to less than 75% by volume.
A method for producing a porous gas diffusion electrode for membrane fuel cells on an ion-conducting polymer membrane comprising coating the membrane with a dispersion of a finely divided electrocatalyst and at least one pore-forming material in a solution of an ion-conducting polymer, said polymer membrane being in a non-acidic, temperature-stable state, heating said membrane during said coating to a temperature in a range of 130.degree. to 170.degree. C., drying said membrane, re-protonating said membrane and said coating with an acid, wherein the pore-forming material is in finely divided form with an average particle size of 0.1 to 10 .mu.m.
A method for producing a porous gas diffusion electrode for membrane fuel cells on an ion-conducting polymer membrane comprising coating the membrane with a dispersion of a finely divided electrocatalyst and at least one pore-forming material in a solution of an ion-conducting polymer, said polymer membrane being in a non-acidic, temperature-stable state, heating said membrane during said coating to a temperature in a range of 130.degree. to 170.degree. C., drying said membrane, re-protonating said membrane and coating said membrane with an acid, wherein the pore-forming material is in finely divided form with an average particle size of 0.1 to 10 .mu.m, said electrode having a total porosity of more than 40 to less than 75% and composed of a bimodal distribution of small pores with an average diameter up to 0.5 microns and large pores with an average diameter from 1 to 20 microns.
A coating composition for preparing a gas diffusion electrode consisting essentially of a dispersion of an acidic, ion-conducting polymer in a solvent therefor, at least one finely divided noble metal containing electrocatalyst and at least one pore-forming material, said composition being free of a hydrophobic polymer.
Dependencies are inferred from the claim text.