Acid Electrolyte Anions Adsorption Effects on IrO2 Electrocatalysts for Oxygen Evolution Reaction

Proton exchange membrane water electrolysis is a promising technology merging the usage of intermittent renewable energy sources with the production of green hydrogen. Anodic oxygen evolution reaction remains the bottleneck of the efficiency of these devices due to sluggish reaction kinetics, high cost, and scarcity of state-of-the-art catalytic materials. Though most research is focused on the discovery of new catalytic materials, understanding the effects of acid electrolyte anions is crucial to designing and optimizing existing electrocatalysts under diverse electrochemical microenvironments. Herein, we systematically study the effects of acid electrolytes on IrO2(110) surface under OER reaction conditions using density functional theory. The potential dependent anion adsorption results show that HPO4(2-) adsorbs strongest followed by SO4(2-), NO3(1-) and ClO4(1-) respectively at 1.6 V (vs. RHE). HPO4(2-) and SO4(2-) block the Ir-active sites by competitively adsorbing with the OER intermediates while ClO4(1-) does not interfere with OER performance. By evaluating dipole-field interactions, surface work function changes, Bader charges of adsorbed anions, and the effects of adsorbed electrolyte anions on the adsorption of OER intermediates, we provide further insights into acid anion electrolyte effects under OER conditions. This expansion of fundamental understanding of the effects of acid electrolyte anion adsorption on IrO2 assists in engineering better performing catalysts with integrated electrolyte microenvironment for OER.