In situ construction of surface oxygen vacancies on N/TiO2 for promoting visible light photocatalytic H2 evolution†

Abstract

Realizing photocatalytic hydrogen evolution under visible light still has many challenges, especially due the contradiction between the dependence of doping on high temperature and the passivation of catalytic active sites caused by high temperature. Herein, a simple method of mixed sintering of thiourea and NH₂-MIL-125(Ti) was adopted to achieve both N doping and surface O_vin situ construction on TiO₂, significantly improving the visible light catalytic hydrogen evolution performance. Experiments confirm that N doping can regulate the band structure and enhance the light absorption range of TiO₂, while the improvement of surface photocatalytic activity mainly depends on surface defects. Experimental and theoretical studies show that N doping regulates the electron distribution of TiO₂ and forms a photogenerated electron transport channel, which promotes the migration of photogenerated electrons. O_V can capture photogenerated electrons and prolong the lifetime of electrons. The H absorption and desorption equilibrium on the catalyst surface can be optimized by O_V for promoting hydrogen evolution. Consequently, under irradiation of light with 365, 385, 400 and 420 nm wavelengths, the average hydrogen evolution rates of the best sample are 14 700, 4850, 720 and 87 μmol g⁻¹ h⁻¹, respectively. This work provides ideas for the design and development of photocatalysts for visible light photocatalytic hydrogen evolution.