Relationship between defect and strain in oxygen vacancy-engineered TiO2 towards photocatalytic H2 generation

Photocatalytic H2 generation is an effective approach to convert solar energy into renewable H2 energy and has drawn great attentions. To improve the catalytic activity, lots of attentions have been paid to developing advanced strategies, of which oxygen vacancy engineering is considered as a promising one. However, oxygen vacancy induced coexistence of defect and strain makes understanding the essential mechanism of enhanced photocatalytic performance elusive and challenging. Here, the classic photocatalyst TiO2 is selected as a paradigm to reveal the relationship between the accompanied defect and strain in boosting H2 generation activity. It is found that oxygen vacancy concentration almost shows a volcano-type trend, while strain exhibits a monotonic decrease with increasing the calcination temperature. An optimal photocatalytic H2 yield of 788 μmol g−1 h−1 is achieved over the TiO2 with high oxygen vacancy concentration but slight strain. This value is 2.5 times higher than the counterpart with low oxygen vacancy concentration and large strain, indicating that oxygen vacancy induced defect instead of strain plays the dominate role in enhancing photocatalytic H2 generation, which is further verified by theoretical calculations and experimental carrier dynamics analysis. This work uncovers the relationship between defect and strain in oxygen vacancy-engineered photocatalysts.