Revealing the Anion Effect on Gas Diffusion Electrode by Bubble Pump Consumption Chronoamperometry

Real-time hydrogen oxidation kinetics inside gas diffusion electrodes (GDEs) for proton exchange membrane fuel cells is determined by the variation of gas diffusion and effective catalytic site density, which are highly related to the electrolyte microenvironment. Here, we investigate the hydrogen oxidation performance of GDEs in three typical acids (H2SO4, HNO3, and HClO4) by bubble pump consumption chronoamperometry (BPCC) with different concentrations and potentials. The adsorption of anions on the catalyst surface leads to the decrease of effective catalytic sites and the variations of surface tension, proportional to anion concentration and applied potential. When further combined with molecular dynamics simulations, the gas diffusion inside the GDE is proven to be in the order SO42– > NO3– > ClO4–, coinciding with the Hofmeister series of anions. Through the BPCC method, this study reveals not only the mechanism of acidic hydrogen oxidation kinetics from the perspective of gas diffusion in GDEs but also new insights into wettability variations induced by electrowetting effects in practical energy conversion systems.