Abstract
Se4+ and N3− ions were used as codopants to enhance the photocatalytic activity of TiO2 under sunlight irradiation. The Se/N codoped photocatalysts were prepared through a simple wet-impregnation method followed by heat treatment using SeCl4 and urea as the dopant sources. The prepared photocatalysts were well characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM) and Raman spectroscopy. The codoped samples showed photoabsorption in the visible light range from 430 nm extending up to 580 nm. The photocatalytic activity of the Se/N codoped photocatalysts was evaluated by degradation of 4-nitrophenol (4-NP). The degradation of 4-NP was highly increased for the Se/N codoped samples compared to the undoped and single doped samples under both UV-A and sunlight irradiation. Aiming to determine the electronic structure and dopant locations, quantum chemical modeling of the undoped and Se/N codoped anatase clusters was performed using Density Functional Theory (DFT) calculations with the hybrid functional (B3LYP) and double-zeta (LanL2DZ) basis set. The results revealed that Se/N codoping of TiO2 reduces the band gap due to mixing of N2p with O2p orbitals in the valence band and also introduces additional electronic states originating from Se3p orbitals in the band gap.
Highlights
In the last few decades, TiO2 has gained an enormous interest due to its potential application in photocatalysis, solar cells and waste remediation
Our Density Functional Theory (DFT) calculations indicated that band gap reduction arises from the contribution of N 2p to the O 2p and Ti 3d states in the valence band (VB) of TiO2
The enhanced photocatalytic activity of the codoped samples may be attributed to the increase in the number of trap sites for electrons and holes, increase in the photoabsorption, smaller particle size and the formation of oxygen vacancies on the surface
Summary
In the last few decades, TiO2 has gained an enormous interest due to its potential application in photocatalysis, solar cells and waste remediation. Our DFT calculations indicated that band gap reduction arises from the contribution of N 2p to the O 2p and Ti 3d states in the VB of TiO2 Based on these results, we attempted to dope TiO2 with Se4+ and N3− ions simultaneously to obtain a more active, visible-light driven photocatalyst. This paper has the purpose of determining the electronic structure, optical and photocatalytic properties of Se/N-codoped TiO2 , to elucidate the chemical nature, the position and the synergistic effect of the dopants on the activity of the photocatalyst For this purpose, a combination of experimental and quantum mechanical methods were used. Modeling of the undoped and Se/N-codoped clusters was performed using DFT calculations to provide a framework for the interpretation of the experimental data and to elucidate the structural and electronic properties of the Se/N-codoped titania
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