Promoting Water Oxidative Hydrogen Peroxide Production by Dynamic Anion Exchange on BiVO4 Photoanodes

Photoelectrochemical (PEC) water oxidative H2O2 production through HCO3– or CO3– medium has been attracting great research interest, yet it suffers from low activity and instability. Herein, we report an anion exchange strategy using a phosphate (PO43–) modified BiVO4 (PBVO) photoanode to enhance the HCO3– oxidation kinetics at the Helmholtz layer of the semiconductor-electrolyte (S-E) interface for superior H2O2 production. As a result, an average PEC H2O2 Faradaic efficiency (FE) of 82.6% was achieved over the optimized PBVO photoanode with the best FE of 92.1% and a production rate of 66.5 μmol h–1. Moreover, the stable PEC water splitting to H2 and H2O2 from full-cell configuration is realized, with a H2O2 accumulation concentration of 2.34 × 10–3 M after 6 h consecutive irradiation. The excellent PEC performance can be ascribed to the fact that PO43–on the surface of the PBVO photoanode exchanges with HCO3– to form the CO3– adsorbed BiVO4 photoanode during the process of water oxidation, kinetically promoting charge transfer at the S-E interface. Simultaneously, H2PO4– that is formed during the exchange of PO43– and HCO3– in the inner Helmholtz layer can stabilize H2O2. This work provides a new insight for understanding PEC oxidation processes in the Helmholtz layer of the S-E interface.