Preparation of Ni-loaded oxygen-enriched vacancy TiO2−x hierarchical micro-nanospheres and the study of their photocatalytic hydrogen evolution performance

Abstract

The introduction of oxygen vacancies (O_v) in TiO₂ has significant effects on improving the light absorption capacity, expanding the light absorption range and inhibiting photo-generated charge recombination. Here, we used hydrochloric acid and urea mixed with TiO₂ hierarchical micro-nanospheres (THS) followed by annealing in an air atmosphere to dope THS with nitrogen and successfully mediated the formation of oxygen defects. Then, the Ni-based promoter is supported on the THS with oxygen vacancy defects by impregnating the metal ions in the solution. Compared with untreated Ni-THS, Ni-THS(O_v) modified by oxygen deficiency has a shorter band gap and photo-generated charge separation efficiency, and its photocatalytic water splitting capacity was also significantly improved. The hydrogen production performance of Ni-THS(O_v) (0.1 wt%) reached 4.88 mmol g⁻¹ h⁻¹ under full-spectrum (UV-vis) irradiation. The synergistic relationship between THS, surface oxygen vacancies and the supported Ni promoters was further investigated.