Piezo-activating oxygen vacancy regulates quantum well effect and p-band center for exceptional photocatalysis

Abstract

Solar catalysis efficiency is severely subject to the insufficient charge separation and inactive surface sites. Building piezoelectric field is established to be effective for anisotropic photocharge separation, and introducing defects can enrich surface reactive sites. However, the relationship between piezoelectric field and surface defect or reaction kinetics remains unclear. Herein, we report piezo-activating oxygen vacancy (OVs) to regulate quantum well effect and p-band center for exceptional photocatalysis in polar BiOIO₃ single crystals. The introduction of piezoelectric field enhances the local charge asymmetry distribution induced by OVs, facilitating electron donating from bulk to surface I atom. Remarkably, the external strain collaborates with OVs to largely reduces the work function of its surface, and induces a larger up-shift of p-band center of I 5p orbitals in BiOIO₃. It indicates a reduction in the occupancy of antibonding-orbital, facilitating the stabilization of O 2p antibonding states and formation of I-O_ads bonds for strong O₂/H₂O adsorption. Thus, oxygen-vacant BiOIO₃ achieves a dramatically improved piezo-photocatalytic degradation efficiency towards various pollutants, outperforming the related piezo-photocatalysts in previous reports. This work reveals the mechanism of piezoelectric field on surface vacancy and surface electronic structure at the atomic level.