Origin of Photocatalytic Activity of Nitrogen-Doped TiO₂ Nanobelts

Abstract

Experiments combined with the density functional theory (DFT) calculation have been performed to understand the underlying photocatalysis mechanism of the nitrogen-doped titania nanobelts. Nitrogen-doped anatase titania nanobelts are prepared via hydrothermal processing and subsequent heat treatment in NH(3). Both the nitrogen content and the oxygen vacancy concentration increase with increasing the NH(3) treatment temperature. Nitrogen doping leads to an add-on shoulder on the edge of the valence band, the localized N 2p levels above the valence band maximum, and the 3d states of Ti(3+) below the conduction band, which is confirmed by DFT calculation and X-ray photoelectron spectroscopy (XPS) measurement. Extension of the light absorption from the ultraviolet (UV) region to the visible-light region arises from the N 2p levels near the valence band and from the color centers induced by the oxygen vacancies and the Ti(3+) species. Nitrogen doping allows visible-light-responsive photocatalytic activity but lowers UV-light-responsive photocatalytic activity. The visible-light photocatalytic activity originates from the N 2p levels near the valence band. The oxygen vacancies and the associated Ti(3+) species act as the recombination centers for the photoinduced electrons and holes. They reduce the photocatalytic activity although they contribute to the visible light absorbance.

A Fe/Fe3O4/N-carbon composite with hierarchical porous structure and in situ formed N-doped graphene-like layers for high-performance lithium ion batteries

“…The peak at 397.8 eV is assigned to sp 2 hybridized N atoms bonded to carbon atoms, and that at 400.2 eV corresponds to pyrrolic N atoms trigonally bonded with sp 2 or sp 3 hybridized carbon atoms. 28 The XPS analyses confirm the existence of pyrrolic nitrogen in the porous composite and are consistent with the C 1s spectrum (Fig. 3c).…”

CO2 Reduction: From the Electrochemical to Photochemical Approach

“…Partially replacing O in the lattice with other nonmetal elements such as B, C, N, S, and P is proven effective ( Figure 11 a) 175. Additional electronic states above the valence band edge introduced by the nonmetal doping were found responsible for the visible‐light response as corroborated by DFT calculations (Figure 11b) and X‐ray photoelectron spectroscopy characterizations 175, 176. Among various nonmetal doping systems, N‐doping is the most widely studied.…”

“…b) Calculated density of state (DOS) of pure TiO 2 and N‐doped TiO 2 with different concentrations of O vacancies. Reproduced with permission 176. Copyright 2009, American Chemical Society.…”

Substitution Boosts Charge Separation for High Solar-Driven Photocatalytic Performance

“…Although some success has been reported in achieving visible light activity by using dopants, the charge carrier trapping and recombination sites induced in the bulk have negative effects on photochemical activity. 7,8 As the layered ternary semiconductors, bismuth oxyhalides (BiOX, X = Cl, Br, and I) with [Bi 2 O 2 ] 2+ slabs sandwiched between halogen atom slabs have drawn extensive attention due to their superior photocatalytic performance, in some cases surpassing that of TiO 2 in UV region. 9−11 However, in contrast to some other Bi-based semiconductors (such as BiVO 4 , Bi 2 WO 6 , and BiFeO 3 ), 12,13 lower visible-light activities of the BiOX need to be enhanced for satisfying practical applications.…”