Comparative study on the visible light driven photocatalytic activity between substitutional nitrogen doped and interstitial nitrogen doped TiO2

• Both substitutional doped and interstitial N-doped TiO2 is prepared by a simple annealing method.
• The photocatalytic activity toward decomposing benzene of N-TiO2 is higher than that of NAM-TiO2.
• The surface hydroxyl group and different location of nitrogen in the lattice is responsible for the distinct photocatalytic activity.
• The presence of oxygen favors the formation of interstitial nitrogen dopant during synthesis.
• The deep Ni-energy level in bandgap tends to form the recombination center.

Nitrogen-doped TiO2 nanomaterial attracts enormous attention due to its excellent visible photocatalytic activity. A simple annealing method assisted by adjusting gas composition to control the positions of nitrogen dopants in TiO2 lattice is presented. The nitrogen doping sites are confirmed by XPS. The photo-degradation results of gaseous benzene under visible light illumination reveal that photocatalytic activity in as-prepared samples containing the substitutional nitrogen species is higher than that in samples containing interstitial nitrogen species. The improvement of photocatalytic performance is ascribed to the increased amounts of surface hydroxyl group in N-TiO2 samples. The efficient separation of electron-hole pairs was also responsible for the enhanced photocatalytic activity. In addition, an important conclusion is pointed out: the presence of oxygen during annealing process has an important effect on the formation of interstitial nitrogen dopants. The present work is believed to have guiding significance for preparing nitrogen-doped TiO2 with high photocatalytic activity.

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