Three Mechanisms for Protecting the Fuel Cell Membrane, Plates and Catalysts

Abstract

The performance of the perfluorinated sulfonic acid polymer electrolyte membrane in PEM fuel cells degrades through a multi-step process: (i) hydroxyl radicals attack on the fluorinated polymer with the release of fluoride ions; (ii) corrosion of the plates and alloy catalysts by the fluoride anions, with the release of base metal cations; (iii) generation of more hydroxyl radicals through Fenton's reaction catalyzed by the metal ions. While fluoride ion release can be greatly reduced through the inclusion of cerium, manganese or sodium ions into the PFSA polymer membrane, we present here an alternative approach for mitigating the membrane degradation. We propose three chemical methods for increasing the overall durability of the fuel cell by interfering with each step of this degradation cycle: the uses of (i) hydroquinones, to neutralize hydroxyl radicals, (ii) aza-crowns for sequestering fluoride anions, and (iii) crown ethers to sequester base metal cations.