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 mu mol h(-1). Moreover, the stable PEC water splitting to H-2 and H2O2 from full-cell configuration is realized, with a H2O2 accumulation concentration of 2.34 x 10(-3) M after 6 h consecutive irradiation. The excellent PEC performance can be ascribed to the fact that PO(4)(3-)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.