Enhanced photocatalytic hydrogen evolution activity of carbon and nitrogen self-doped TiO2 hollow sphere with the creation of oxygen vacancy and Ti3+

Introducing oxygen vacancies and Ti3+ into TiO2 is thought to be an effective method of increasing the utilization of sunlight and promoting the efficiency of electron transfer. In this work, novel carbon and nitrogen self-doped TiO2 hollow spheres (CNTH) with oxygen vacancies and Ti3+ were synthesized by a one-pot hydrothermal strategy in H2O-C2H5OH-HF-H2O2 mixed solution with TiCN as a precursor of anatase TiO2 and self-doping source of N and C. The presence of oxygen vacancies and Ti3+ in the resulting CNTH photocatalyst was supported by electron paramagnetic resonance (EPR) and X-ray absorption near-edge structure spectroscopy (XANES). X-ray photoelectron spectroscopy (XPS) analysis showed that the C and N atoms were successfully self-doped into TiO2 lattice, which resulted in the CNTH materials exhibiting the enhanced absorption in the UV-visible region with a clear red shift at the absorption edges. The electronic structure of CNTH was examined by first-principle density functional theory (DFT) calculations, which further confirmed the optical properties of CNTH for the enhanced visible-light absorption properties and the red-shift phenomenon of the absorption edges. The resulting CNTH photocatalyst showed enhanced visible-light photocatalytic activity for H-2 production. The enhanced activity of CNTH was due to the introduction of C and N self-doping and the existence of oxygen vacancies and Ti3+. The former can promote the photocatalytic reactions of the photogeneration electrons and holes on CNTH under visible-light irradiation, while the latter create more active sites and prolong the life time of electrons and holes by their donor states. (C) 2018 Elsevier Ltd. All rights reserved.