A facile acid treatment for P25 modification with enhanced photocatalytic H₂ evolution-effect of Brønsted acid sites and oxygen vacancies

Acid treated P25 catalysts (HP25-x, x represents the treatment temperature) were successfully fabricated via a simple soaking and drying process for photocatalytic H₂ production. After acid treatment, a substantial number of -OH groups were obtained on the surface of HP25-60, which can act as Brønsted acid sites providing hydrogen protons for H₂ generation. Besides, more oxygen vacancies and Ti³⁺ sites were also created on the HP25-60 surface after acid treatment, which could enhance the carrier separation and transfer efficiency by capturing more electrons and holes, respectively. The H₂ production over HP25-60 reached 4853 μmol h^-1 with Pt as a co-catalyst, which is 7.1 times higher than 679 μmol h^-1 of bare TiO₂. Three favorable factors for H₂ photogeneration, i.e. Brønsted acid sites, oxygen vacancies and Ti³⁺ sites, can be introduced on a catalyst surface via a simple one-step acid strategy, which can be applied as a universally-applicable modification method for valence-alternative metal oxide semiconductors for enhanced H₂ photogeneration.