Type II heterojunction promotes photoinduced effects of TiO2 for enhancing photocatalytic performance

Obtaining hydrogen energy from photocatalytic water splitting driven by solar energy is a promising strategy to solve the global energy crisis. Herein, by taking the photoinduced activation effects of TiO2, we obtained a Ti3+ self-doped TiO2 (Ti3+-TiO2). In situ characterization revealed that the presence of Ti3+ is attributed to the reduction reaction of Ti4+ on the TiO2 surface under UV light irradiation. The research results prove that the optical properties of TiO2 are modified by the active species Ti3+; the recombination rate of the photogenerated carriers is significantly decreased, and Ti3+-TiO2 exhibits a hydrogen production rate which is 1.7 times superior than that of pristine TiO2. To further enhance the self-activation effect of TiO2, we constructed a type II heterojunction TiO2/UiO-66-NH2 structure to transfer photoexcited electrons to TiO2, which gives a higher concentration and duration of the active species Ti3+. Ti3+-TiO2/UiO-66-NH2 shows improved photocatalytic hydrogen evolution activity with a rate 3.2 times better than that of pristine TiO2 due to the synergistic function of oxygen vacancies and Ti3+. A novel perspective was adopted in this work to observe the dynamic variation of active species and electron transfer pathways during TiO2 photocatalytic reactions. Since Ti3+ is generated on the TiO(2)in situ, this work could be extended to TiO2-based photocatalysts.

Automated summary

This study successfully prepared Ti3+-doped TiO2 by utilizing the photocatalytic water splitting properties of TiO2. The presence of Ti3+ significantly reduced the recombination rate of photogenerated carriers and resulted in a higher hydrogen production rate compared to pristine TiO2. Furthermore, a type II heterojunction TiO2/UiO-66-NH2 was constructed to enhance the self-activation effect of TiO2 and improve the photocatalytic hydrogen evolution activity.