Abstract
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.
Highlights
The increasing consumption of fossil energy has caused serious energy crisis and environmental problems
In order to further prove that the changes in the surface structure of black TiO2 nanotube arrays are caused by oxygen vacancies, electron paramagnetic resonance (EPR) was used to detect the presence of oxygen vacancies
The effect of oxygen vacancy concentration was investigated on the crystalline phase, electronic structure, and catalytic activity of TiO2 through density functional theory (DFT) calculations and experiments
Summary
The increasing consumption of fossil energy has caused serious energy crisis and environmental problems. Solar energy is a kind of renewable green energy, and its use for semiconductor-based photocatalytic water splitting to produce hydrogen has been considered as one of the most important solutions to world energy crisis [3]. TiO2 is a wide band gap semiconductor (rutile: 3.0 eV; anatase: 3.2 eV), and only absorbs ultraviolet light that accounts only for about 5% of the solar energy. Self-doped oxygen vacancy has been extensively studied experimentally and theoretically. This doping method features low cost, and the ease in preparation and high effectiveness [11, 12]
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