Investigation of in-situ catalytic combustion in polymer-electrolyte-membrane fuel cell during combined chemical and mechanical stress test

Abstract

This study is focused on elucidating the catalytic combustion phenomenon in proton-exchange-membrane fuel cells. A visualization cell and an infrared (IR) camera are used to capture the thermal behavior under combined chemical and mechanical accelerated stress conditions in situ. Catalyst coated membrane (CCM) embedded in the cell is subjected to a relative humidity (RH) cycling test under open-circuit voltage (OCV) conditions at atmospheric pressure and at a cell temperature of 80 °C. The temperature distribution on the gas diffusion layer surface at the cathode is captured through a high-transmittance glass window (ZnS window). Continuous IR imaging revealed a hot spot at ca. 500 RH cycles, suggesting the existence of a pinhole in the degraded CCM and the occurrence of catalytic combustion there. The occurrence of the hot spot coincides with the time at which the electrochemical indicators detect membrane failure, i.e., hydrogen crossover rate, OCV. Furthermore, a post mortem analysis revealed a 105-μm diameter pinhole, the position of which matched that of the hot spot. This pinhole is responsible for the rapid increase in the hydrogen crossover rate as well as the significant decrease in the OCV at 500 RH cycles until the end of the durability test.