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

The introduction of oxygen vacancies (Ov) 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(Ov) 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(Ov) (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.