Synergistic vacancy defects and the surface hydrophobic-to-superhydrophilic wetting engineering in W/S co-doped BiOI for enhanced photocatalytic hydrogen evolution

Abstract

Bismuth oxyhalide (BiOI) has been used for photoelectrochemical catalysis in the field of catalytic hydrogen evolution, but it in a single-phase form has hardly been reported for photocatalytic hydrogen evolution reaction (PHER). Herein, we designed a W/S co-doped BiOI-based superhydrophilic catalyst with oxygen vacancy-rich defects and heterovalent valence states for efficient PHER under visible light. The W/S doping in BiOI not only adjusts the energy band structure and expands the visible light response range, but also transforms its hydrophobicity into superhydrophilicity, with which the gas bubble amount can be reduced and PHER activity enhanced. The introduction of sulfur regulates the content of oxygen vacancies which enhance the active surface sites for capturing water molecules and activating the H-O-H bond. The added tungsten exists in different valence states of W6+ and W5+ which is beneficial for electron hopping and PHER activity. The W/S-BiOI-3 with the suitable W/S doping content exhibits the highest visible-light PHER rate of 9.46 mmol·g−1·h−1, with an apparent quantum efficiency (AQE) of 9.7 % at 420 nm. W/S-BiOI-3 shows excellent PHER activity, stability, and durability, which provides a feasible scheme for other bismuth-based halogen oxides to be used in PHER.