Mechanisms of Visible Light Photocatalysis in N-Doped Anatase TiO₂with Oxygen Vacancies from GGA+U Calculations

Abstract

We have systematically studied the photocatalytic mechanisms of nitrogen doping in anatase TiO 2 using first-principles calculations based on density functional theory, employing Hubbard U (8.47 eV) on-site correction. The impurity formation energy, charge density, and electronic structure properties of TiO 2 supercells containing substitutional nitrogen, interstitial nitrogen, or oxygen vacancies were evaluated to clarify the mechanisms under visible light. According to the formation energy, a substitutional N atom is better formed than an interstitial N atom, and the formation of an oxygen vacancy in N-doped TiO 2 is easier than that in pure TiO 2 . The calculated results have shown that a significant band gap narrowing may only occur in heavy nitrogen doping. With light nitrogen doping, the photocatalysis under visible light relies on N-isolated impurity states. Oxygen vacancies existence in Ndoped TiO 2 can improve the photocatalysis in visible light because of a band gap narrowing and n-type donor states. These findings provide a reasonable explanation of the mechanisms of visible light photocatalysis in N-doped TiO 2 .

Controlled nitrogen insertion in titanium dioxide for optimal photocatalytic degradation of atrazine

“…A signicant increase of light absorption at lower photon energy levels was observed for all the doped TiO 2 samples, extending the absorption coverage towards 400-550 nm of the visible light region. Furthermore, the work done by H. Wu et al 46 suggests that the formation of oxygen vacancies in the presence of nitrogen is easier as compared to naked TiO 2 . This claim is further supported by the work of Xiang et al, 25 where from rst principle density functional theory (DFT) calculations, an interstitial Nprecursor can induce local states above the valence band and is responsible for the visible light response.…”

TiO2 mesocrystal with nitrogen and fluorine codoping during topochemical transformation: Efficient visible light induced photocatalyst with the codopants

“…Compared with those for pristine TMC, 2.1 ps ( 1 ), 36 ps ( 2 ), and 1288 ps ( 3 ) in Table 2, it is shown that the slower recombination process on NFT-500 corresponds to the hole localized on the N 2 p state in Fig. 7B [37,38]. On the other hand, the efficient charge separation of NFT-500 was observed with the lower photocatalytic efficiency under the UV irradiation compared to that for pristine TMC, suggesting the low yield of hydroxyl radical because of less positive potential of N in the localized midgap state (Fig.…”

Electronic Structure and Optical Properties of N/Si-Codoped Anatase TiO2Evaluated Using First Principles Calculations

“…We previously used the DFT + U method and the following formalism to describe the exchange and correlation potential [6,24]:…”

“…The DFT + U is a method of correcting the underestimation of the bandgap and involves adding an orbitaldependent term to the DFT potential; it has previously been used to describe the electronic structures of transition-metal oxides [22][23][24][25]. Thus, we used the DFT + U method to more accurately represent the electronic structure and optical properties of N/Si-codoped TiO 2 .…”