Suppression of Membrane Degradation Accompanied with Increased Output Performance in Fuel Cells by Use of Silica-Containing Anode Catalyst Layers

Polymer electrolyte membranes (PEMs) for fuel cells are chemically degraded by the attack of ·OH radicals generated from the decomposition of H₂O₂, which is predominantly produced at the Pt/C hydrogen anode. The incorporation of conventional radical scavengers into the PEM suffers from a decrease in the output performance. We, for the first time, demonstrate that the addition of hygroscopic silica nanoparticles (NPs) to the Pt/C anode catalyst layer provides a remarkably prolonged (ca. 4 times) lifetime of a Nafion membrane in an accelerated stress test and open circuit voltage (OCV) holding at 90 °C, accompanied by improved output (I-E) performances at low relative humidity. It has been found that the use of silica NPs decreases H₂O₂ formation rate from the OCV to a practical H₂ oxidation potential in a half-cell using 0.1 M HClO₄ at 90 °C and provides reduced ohmic resistance (increase in water content) and effective utilization of Pt cathode catalyst in a single cell, by which the improvement of the durability of the PEM and increased output performance are explained rationally.