Synergistic V/S co-doping induces dual-site activation and superhydrophilicity in BiOI for enhanced photocatalytic hydrogen evolution

Abstract

The intrinsically limited density of active sites and hydrophobic surface characteristics of BiOI fundamentally constrain its photocatalytic hydrogen evolution reaction (PHER). Herein, we demonstrate a one-step hydrolysis strategy to construct V-cation/S-anion co-doped BiOI featuring heterovalent vanadium states, abundant oxygen vacancy (Vo) defects, and a superhydrophilic surface. The optimized V/S-BiOI-3 exhibits ideal n(V4+)/n(V5+) ratios of 21.8% and a high Vo concentration of 22.7%, delivering an impressive PHER rate of 1260.8 μmol·h-1 and an apparent quantum efficiency (AQE) of 12.9% at 420 nm, while maintaining excellent stability with only a 4.8% decrease after 6 consecutive cycles. Mechanistic investigations reveal that V/S co-doping strategy simultaneously tunes the band structure of BiOI and converts its originally hydrophobic interface into a superhydrophilic surface, greatly enhancing water affinity and decreasing interfacial adhesion. Vanadium incorporation induces valence modulation from V5+ to V4+, facilitating charge transfer, while generating Vo defects that serve as active sites for adsorbing water molecules and activating H-O-H bonds. Meanwhile, sulfur incorporation reinforces O 2p-S 3p orbital hybridization, thereby stabilizing the BiOI during photocatalysis. This work highlights hetero cation/anion co-doping as a robust and generalizable strategy for defect–state engineering in bismuth oxyhalides, offering new opportunities for advancing high-efficiency solar-to-hydrogen conversion.