Mechanism of Bicarbonate-Enhanced Solar Oxidation of Water to Hydrogen Peroxide over BiVO4

Proper coupling of electrode and electrolyte chemistries can enhance both activity and selectivity in photoelectrocatalysts, but the mechanisms for efficient interface engineering are not well understood. This study examines hydrogen peroxide production via solar-driven water oxidation on a BiVO4 photoanode in the presence of bicarbonate ions. Using ab initio calculations, we show that adsorbed HCO3− species act as reaction centers, promoting selective H2O2 production. Hybrid functional first-principles molecular dynamics simulations reveal that surface hole polarons accelerate H2O2 formation by stabilizing the transient HCO4− intermediate. In this process, surface-bound HCO3− serves as a hole acceptor, facilitating reaction kinetics. Our findings offer mechanistic insights into the activation of electrolytic species by photo-generated charge carriers, enhancing selectivity for the thermodynamically less favorable product (H2O2).