Abstract
Up to now, the explanation for the origin of enhanced photocatalytic activity of N doped TiO2 (N-TiO2) with H incorporation, which is observed in experiment, is still lacking. In our work, the effects of hydrogenation on the stability and electronic properties of N-TiO2 have been systematically investigated by first-principles calculations. Our results of the study on stability demonstrate that, both full and part hydrogenation could stabilize N-TiO2 by largely reducing the formation energy of N doping under Ti-rich conditions. Moreover, the calculated results on the electronic structure show that, for the completely hydrogenated N-TiO2, band gap becomes slightly larger, which is caused by the full passivation for unpaired electron from N atom. However, for the partially hydrogenated N-TiO2, due to the interaction between hydrogenated and unhydrogenated N atoms, its valence band maximum shifts to higher energy by 0.32 eV and the valence band states mix with the wide band-gap states, which results in a higher light absorption capacity and carrier separation. Our results not only explain the enhancement of visible light photocatalytic activity experimentally found in N-TiO2 specimen with H incorporation, but also indicate that, tuning the hydrogenation degree is a hopeful routine to improve the photocatalytic performance of N-TiO2.
Highlights
Due to the ever-growing energy crisis and environmental pollution problems, the development of clean, environmentally friendly and sustainable alternative energy sources is urgently required
Since the discovery of “Honda-Fujima” effect [1], photocatalytic water splitting has been considered as an optimal pathway for hydrogen production, which has received extensive attention for decades [2,3,4,5,6,7]
Efficient and stable photocatalysts plays a key role in improving the efficiency of photocatalytic water splitting
Summary
Due to the ever-growing energy crisis and environmental pollution problems, the development of clean, environmentally friendly and sustainable alternative energy sources is urgently required. Anatase titanium dioxide (TiO2) has attracted a great interest for the application of hydrogen generation [8] and environmental cleanup [9] It possesses strong photocatalytic activity, high physical and chemical stability, and nontoxicity [10], its energy conversion efficiency is extremely low, which is caused by its large band gap (Eg) (~3.2 eV) [11] and high electron-hole recombination rate. The Vo introduced in the bulk TiO2 is prone to become recombination centers for photogenerated electron-hole pairs, and the visible light photocatalytic activity of N-TiO2 does not improve with N doping concentration increase [24]. Based on the results above, the influence of hydrogenation on the VL photocatalytic activity of N-TiO2 was further discussed
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