Impact of Intrinsic Defects on the Electronic Structure and Band Alignment of (010) and (001) BiVO4 Surfaces for Photocatalytic Water Splitting: A Hybrid DFT Study

Abstract

Intrinsic defects and crystal-facet engineering are widely recognized as effective approaches for understanding, controlling, and improving the photocatalytic performance of materials. However, the interplay between the most favorable intrinsic defects and the electronically active exposed facets remains largely unexplored and poorly understood. Herein, hybrid density functional theory (DFT-HSE06) calculations are employed to investigate the influence of the thermodynamically most preferred defect complex consisting of three V-on-Bi antisites coupled with two additional Bi vacancies on the electronic structure, band alignment, and carrier localization characteristics of the two most promising predominant (010) and (001) BiVO4 surfaces for photocatalytic water splitting. The presence of these intrinsic defects induces an electronic band gap reduction of 0.5–0.6 eV driven primarily by conduction-band lowering through partial V5+ → V4+ reduction. Even though this trend leads to improved visible-light harvesting potential of BiVO4, it brings completely different facet-dependent water redox and charge-carrier transport characters. Among the two explored surfaces, only the self-defective (001) facet maintains a well-pronounced carrier delocalization and preserves its thermodynamic compatibility with both hydrogen evolution reaction and oxygen evolution reaction, indicating a comparatively defect-tolerant electronic structure. These findings clarify the role of intrinsic surface defects in tuning BiVO4 activity and provide guidance for designing efficient defect-engineered photocatalysts for solar-driven hydrogen production from water splitting reactions.