New Insights into the Origin of Visible Light Photocatalytic Activity of Nitrogen-Doped and Oxygen-Deficient Anatase TiO₂

Abstract

The spin-polarized plane-wave pseudopotential method, based on density-functional theory, has been used to calculate the electronic band structures and the optical absorption spectra of nitrogen-doped and oxygen-deficient anatase TiO2. The calculated results are in good agreement with our experimental measurements. These ab initio calculations reveal that the optical absorption of nitrogen-doped TiO2 in the visible light region is primarily located between 400 and 500 nm, while that of oxygen-deficient TiO2 is mainly above 500 nm. These results have important implications for the understanding and further development of photocatalytic materials that are active under visible light.

Understanding the Reaction Mechanism of Photocatalytic Reduction of CO2 with H2O on TiO2-Based Photocatalysts: A Review

“…Electrons could be excited from the VB to the defects donor state (red dashed line) under visible light illumination. The lifetime of electrons in the defects donor state is much longer than that on the CB (Lin et al, 2005;Xing et al, 2013), which facilitates the formation of superoxide radicals by attachment of electrons to oxygen. Meantime, the holes left in the VB accelerate the generation of free OH radicals.…”

“…It was found that doping of TiO 2 with nonmetal elements improved the visible light activity, depending on the type and the concentration of nonmetal dopants. Among the various nonmetal dopants, N-doped TiO 2 is widely used in photooxidation of organics (Lin et al, 2005;Chen and Burda, 2008;Gai et al, 2012) and in CO 2 photoreduction as well (Varghese et al, 2009;Fan et al, 2011;Zhang et al, 2011;Li et al, 2012;Zhang et al, 2012). However, the origin of the visible light activity of N-doped TiO 2 has long been debated.…”

“…Doped N gives rise to an impurity state above the TiO 2 VB. The mixing of N 2p orbital and the TiO 2 VB narrows the band gap of TiO 2 and extends the photoresponse of TiO 2 to the visible light region (Lin et al, 2005;Chen and Burda, 2008;Li et al, 2012). Visible light irradiation will induce the electron transfer from the nonmetal impurity state to the CB, while the photogenerated holes left in the impurity state may oxidize H 2 O to O 2 or OH groups to OH• radicals.…”

Synergistic Effects on Band Gap-Narrowing in Titania by Codoping from First-Principles Calculations

“…For example, N-doped TiO 2 is considered to be a promising photocatalyst, and it has been investigated widely, both by experimental and theoretical methods [2]. However, due to strongly localized N 2p states at the top of valence band [3], the photocatalytic efficiency of N-doped TiO 2 decreases because isolated empty states trap an appreciable proportion of photo-excited electrons and reduce photo-generated current [4]. Besides N-doped TiO 2 , C-doped TiO 2 also shows photocatalytic activity under visible-light [5].…”

Evidence for TiON sputtered surfaces showing accelerated antibacterial activity under simulated solar irradiation

“…3 lead to TiON samples with a higher optical absorption (Subramanian et al, 2011) due to the introduction of Ninterstitial sites doping the TiO 2 with O-vacancies (Valentin et al, 2005). This in turn leads to a larger amount charge transfer sites in the visible region (Lin et al, 2005;Lee et al, 2009 …”