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. The anodic oxygen evolution reaction remains the bottleneck of the efficiency of these devices due to sluggish reaction kinetics, high cost, and the 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 in diverse electrochemical microenvironments. Herein, we systematically study the effects of acid electrolytes on the IrO2(110) surface under OER reaction conditions using density functional theory. The potential-dependent anion adsorption results show that HPO42- adsorbs the strongest, followed by SO42-, NO3-, and ClO4- respectively at 1.6 V (vs RHE). HPO42- and SO42- block the Ir-active sites by competitively adsorbing with the OER intermediates while ClO4- 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 the OER intermediates, we provide further insights into acid anion electrolyte effects under the 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.