Psesudocubic Phase Tungsten Oxide as a Photocatalyst for Hydrogen Evolution Reaction

Defect and phase engineering can effectively tune the activity of photocatalysts by altering their band structure and active site configuration. Herein, we report the phase-controlled synthesis of tungsten oxide (WO3) nanoplates via a wet-chemical approach. By adjusting the ratio of trioctylphosphine and trioctylphosphine oxide, oxygen vacancies are induced in WO3 at a relatively low temperature, accompanying the crystal structure transition from monoclinic to orthorhombic or pseudocubic phase. The experimental results and DFT calculations reveal that the increased oxygen vacant sites in WO3 lead to the upshift in both conduction band minimum and valence band maximum. The reformed band structure of reduced WO3 samples (WO3–x) enables the photocatalytic hydrogen evolution without cocatalyst at a maximum steady rate of 340 μmol g–1 h–1 under simulated sunlight. Our work demonstrates a simple and effective strategy of introducing oxygen vacancy to WO3 for band structure tuning, which may be further extended to other metal oxide systems.