Self-Doping Surface Oxygen Vacancy-Induced Lattice Strains for Enhancing Visible Light-Driven Photocatalytic H2 Evolution over Black TiO2

The synergistic effect of surface oxygen vacancy with induced lattice strains on visible light-driven photocatalytic H2 evolution over black TiO2 was investigated. Experimental measurements and theoretical calculations on the lattice parameters of black TiO2 show that surface oxygen vacancies induce internal lattice strain during two-step aluminothermic reduction, which regulates the band structure and optimizes the photoinduced charge behavior of black TiO2. The hydrogen evolution rate of black TiO2 with strain modification shows a 12-fold increase to 1.882 mmol/g· h (equal to 4.705 μmol/cm2·h) under visible light illumination. The metastable state caused by the surface oxygen vacancies leads to the formation of a high-energy surface, which enhances visible light absorption and improves the photoinduced charge separation efficiency. Furthermore, the internal lattice strain provides the driving force and channel for the directional movement of photoinduced electrons from the bulk to the high-energy surface for photocatalytic H2 evolution. This strategy provides a new method for designing a high-performance photocatalyst for H2 production.