Unravelling the Role of Titanium/Oxygen Dual Defects of SrTiO3 in Boosting Optical Absorption and Carrier Dynamics for Efficient Hydrogen Production Induced by Visible Light

Defect engineering can effectively promote light absorption and carrier dynamics of semiconductor photocatalysts. However, it is still difficult to modulate the distribution and concentration of defects in the photocatalyst via a facile strategy. The perovskite SrTiO3 is a promising semiconductor photocatalyst for hydrogen production, but its performance is restricted by limited UV absorption and severe carrier recombination. Herein, we develop a visible light-responsive SrTiO3 photocatalyst with Ti3+ and oxygen vacancies distributed both in the bulk and on the surface through a solvothermal synthesis coupled with light illumination. In situ EPR and XPS disclose that bulk defects are produced during the solvothermal synthesis, while the surface defects can be generated by light irradiation. The concentration of Ti3+ and oxygen vacancies can be facilely adjusted by varying the solvothermal time, resulting in the regulation of visible absorption in the range of 450–650 nm. Density functional calculations demonstrate the formation of an in-gap band consisting of defect energy levels, which induces a two-step electron transition and accounts for the visible light response. As revealed by synchrotron radiation X-ray absorption spectroscopy, ultrafast transient absorption spectroscopy, and electrochemical analysis, the increase of defect concentration leads to the decrease of Ti–O coordination number as well as the increase of carrier lifetime and carrier density, which ensures promoted carrier dynamics and boosted hydrogen evolution activity driven by visible light. The present research uncovers the role of defects in tuning light absorption and carrier dynamics and opens new opportunities for achieving highly efficient solar energy conversion.