Optimization of the BiO8 polar group of BiVO4 by Cl--embedded modification to manipulate bulk-surface carrier separation for achieving efficient Piezo-PEC water oxidation

Abstract

BiVO4 is a promising photoanode material. However, achieving only a 2.67 % maximum ABPE while having a theoretical solar conversion efficiency of 9.2 % highlights the need for an effective carrier regulation strategy. In this study on the piezoelectric material BiVO4, Cl--embedded modification through synthetic post-treatment changes the oxygen evolution reaction (OER) pathway and suppresses surface charge recombination. In addition, the surprising finding of Cl- bonding with Bi3+ causing distortion in the BiO8 polar groups not only enhances the piezoelectric response but also significantly improves the performance of piezo-photoelectric chemical (Piezo-PEC) water oxidation. In the absence of any co-catalyst or sacrificial agent, the photocurrent density of Cl--embedded modified BiVO4 reached 0.268 mA/cm2 at 1.23 VRHE (5 times that of bare BiVO4). The data indicate that the piezoelectric polarized electric field successfully reduces electron-hole recombination. Cl--embedded modification amplifies the electric field intensity of the surface electric dipole in an ultrasonic environment, facilitating hole access to the catalytically active sites on the surface. Furthermore, the modified surface layer creates a rapid channel for hole migration, with the hole trapping process intricately linked to isolated electrons and intermediate Cl atoms. This embedded modification of polar groups serves as a reference for further exploration into the macroscopic polarization of piezoelectric materials and offers an optimization concept for the field of Piezo-PEC catalysis.