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

Abstract

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.