Suppression of Chemical Degradation of Nafion Membrane by Use of Sulfonated Polyphenylene Ionomer in the Anode Catalyst Layer

The effect of electrolyte binders (ionomers) in the anode catalyst layer (ACL) on the chemical degradation rate of polymer electrolyte membranes (PEMs) in fuel cells was examined in a single cell with an accelerated stress test (AST) at 90 °C, while the H 2 O 2 formation rates, j (H 2 O 2 ), and activities for the hydrogen oxidation reaction (HOR) at the ionomer-covered Pt/C catalysts were measured in a half cell with 0.1 M HClO 4 solution at 80 and 90 °C. A sulfonated polyphenylene (SPP-QP) and conventional Nafion were used as the ionomer with Nafion as the PEM. It was demonstrated that the PEM degradation rate decreased remarkably with use of SPP-QP together with lower Pt-loading on carbon support. The suppression of H 2 O 2 formation via a specific adsorption of SPP-QP on Pt together with its low O 2 permeability contributed to the longer lifetime of PEM in the AST.