Effect of oxygen vacancy concentration on the photocatalytic hydrogen evolution performance of anatase TiO2: DFT and experimental studies

Oxygen vacancies (OVs) are important for changing the geometric and electronic structure as well as the chemical properties of anatase TiO2. In this work, we performed a density functional theory (DFT) calculation on the electronic structure and catalytic performance of anatase TiO2 (101) with different numbers of OVs. A comparison of the measured XRD results with the simulated ones of TiO2 demonstrates that OVs can cause changes in the crystal structure. The changes in the electronic structure (Mulliken charges, band structure, and partial density of states) and water splitting on TiO2 (101) surfaces were investigated as a function of oxygen vacancy concentration. The results show that the introduction of OVs forms impurity levels below the conduction band of Ti 3d orbitals, through which electrons can gradually transit from VB to CB. However, when oxygen vacancy concentration is too high, the maximum electron transition energy increases and the promotion effect of OVs on water splitting is weakened. This work would provide more enlightenment and information for the design of defective TiO2 with higher photocatalytic activity.