Interfacial oxygen vacancy layer of a Z-scheme BCN–TiO2 heterostructure accelerating charge carrier transfer for visible light photocatalytic H2 evolution

Abstract

All-solid-state Z-scheme BCN–TiO₂ binary heterostructures with a surface oxygen vacancy layer as the contact interface are fabricated by NaBH₄ reduction and ball milling. The effect of the surface oxygen vacancy layer of BCN–TiO₂ binary heterostructures on the charge carrier transfer and photocatalytic hydrogen evolution was thoroughly investigated. UV-vis diffuse reflection spectra results reveal that the surface oxygen vacancy can extend the light absorption from the UV to the visible-light region for BCN–TiO₂ binary heterostructures. The steady-state/time-resolved photoluminescence spectra exhibit an increased charge carrier lifetime, improved charge carrier separation efficiency and strengthened direct Z-scheme charge transfer process for BCN–TiO_2−x heterostructures. As expected, the BCN–TiO_2−x heterostructures exhibited a higher visible-light photocatalytic efficiency, about 7 and 11 times higher than that of the pure TiO₂ and BCN samples. Namely, the photocatalytic activity of hydrogen evolution can be greatly promoted by constructing the surface oxygen vacancy layer. This work provides a new pathway to construct an efficient contact layer for the direct Z-scheme system to improve the charge carrier separation and transfer and thereby improve the photocatalytic activity.