Promoting Water Oxidative Hydrogen Peroxide Production by Dynamic Anion Exchange on BiVO<sub>4</sub> Photoanodes
Shipeng Wan, Jie Jin, Chaoran Dong, Yuan Lü, Qin Zhong, Kan Zhang, Jong Hyeok Park
Abstract
Photoelectrochemical (PEC) water oxidative H 2 O 2 production through HCO 3 – or CO 3 – 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 (PO 4 3– ) modified BiVO 4 (PBVO) photoanode to enhance the HCO 3 – oxidation kinetics at the Helmholtz layer of the semiconductor-electrolyte (S-E) interface for superior H 2 O 2 production. As a result, an average PEC H 2 O 2 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 H 2 and H 2 O 2 from full-cell configuration is realized, with a H 2 O 2 accumulation concentration of 2.34 × 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 HCO 3 – to form the CO 3 – adsorbed BiVO 4 photoanode during the process of water oxidation, kinetically promoting charge transfer at the S-E interface. Simultaneously, H 2 PO 4 – that is formed during the exchange of PO 4 3– and HCO 3 – in the inner Helmholtz layer can stabilize H 2 O 2 . This work provides a new insight for understanding PEC oxidation processes in the Helmholtz layer of the S-E interface.