Graphitic C3N4 nanosheet-sensitized brookite TiO2 to achieve photocatalytic hydrogen evolution under visible light

Abstract

Brookite TiO₂ was regarded as one of the most promising semiconductor materials in the field of photocatalytic H₂ production. However, the low utilization efficiency of solar energy and high recombination rate of photo-induced carriers have hampered its application. To solve the issues stated above, novel g-C₃N₄ nanosheet/brookite TiO₂ composite materials (TCN) with different contents of g-C₃N₄ nanosheets have been synthesized via an in situ TiO₂ growth approach. The as-prepared TCN samples showed much higher visible-light-driven photocatalytic hydrogen evolution rate than pure g-C₃N₄ nanosheets. The optimal TCN sample with a g-C₃N₄ nanosheet content of 50% exhibited a H₂ evolution rate of 68.76 μmol h⁻¹, which was 1.55 times greater than pure g-C₃N₄ nanosheets and 6.8 times greater than bulk g-C₃N₄ under visible light irradiation. Results from X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy suggest that close interfacial connections between g-C₃N₄ nanosheets and brookite TiO₂ had been formed. Photoelectrochemical tests confirmed that the enhancement of photocatalytic H₂ evolution activity resulted from superior electron transport and charge separation ability of the TCN composite materials.