Effect of Fe Concentration on Fe-Doped Anatase TiO2from GGA +UCalculations

Hsuan-Chung Wu,Syuan-Wei Lin,Sheng-Hong Li

doi:10.1155/2012/823498

Hsuan-Chung Wu, Syuan-Wei Lin + Show 1 more

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https://doi.org/10.1155/2012/823498

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Abstract

To comprehend the photocatalytic mechanisms of anatase <svg style="vertical-align:-3.21404pt;width:55.6875px;" id="M1" height="14.8" version="1.1" viewBox="0 0 55.6875 14.8" width="55.6875" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,14.8)"> <g transform="translate(72,-60.16)"> <text transform="matrix(1,0,0,-1,-71.95,63.41)"> <tspan style="font-size: 12.50px; " x="0" y="0">T</tspan> <tspan style="font-size: 12.50px; " x="7.5268059" y="0">i</tspan> </text> <text transform="matrix(1,0,0,-1,-60.95,60.28)"> <tspan style="font-size: 8.75px; " x="0" y="0">1</tspan> </text> <text transform="matrix(1,0,0,-1,-56.57,60.28)"> <tspan style="font-size: 8.75px; " x="0" y="0">−</tspan> <tspan style="font-size: 8.75px; " x="5.99512" y="0">𝑥</tspan> </text> <text transform="matrix(1,0,0,-1,-45.26,63.41)"> <tspan style="font-size: 12.50px; " x="0" y="0">F</tspan> <tspan style="font-size: 12.50px; " x="6.9016562" y="0">e</tspan> </text> <text transform="matrix(1,0,0,-1,-32.81,60.28)"> <tspan style="font-size: 8.75px; " x="0" y="0">𝑥</tspan> </text> </g> </g> </svg>O<sub >2</sub> with various concentrations of Fe, this study performed first principles calculations based on density functional theory with Hubbard U on-site correction to evaluate the crystal structure, impurity formation energy, and electronic structure. We adopted the effective Hubbard U values of 8.47 eV for Ti 3d and 6.4 eV for Fe 3d. The calculations show that higher concentrations of Fe are easily formed in anatase TiO<sub >2</sub> due to a reduction in the formation energy. The band gap of Fe-doped TiO<sub >2</sub> decreases Fe doping level increases as a result of the overlap among the Fe 3d, Ti 3d, and O 2p states, which enhances photocatalytic activity in the visible light region. Additionally, a broadening of the valence band and Fe impurity states within the band gap might also contribute to the photocatalytic activity.

Highlights

The increase in global pollution has led researchers to search for new techniques and materials to promote environmental protection
A broadening of the valence band and Fe impurity states within the band gap might contribute to the photocatalytic activity
The results indicate that the visible light activity in Fe3+-doped TiO2 is due to the introduction of additional electronic states within the band gap

Summary

Introduction

The increase in global pollution has led researchers to search for new techniques and materials to promote environmental protection. Some experimental results [20, 21] have found that Fe doping in TiO2 could narrow the band gap of TiO2, thereby increasing the efficiency of the photocatalysis in the visible range. The results indicate that the visible light activity in Fe3+-doped TiO2 is due to the introduction of additional electronic states within the band gap. Most theoretical calculations have greatly underestimated the band gap of TiO2 due to the adoption of the conventional DFT method, which is known to include an insufficient description of the on-site Coulomb interaction between electrons occupying the Ti 3d orbitals.

Calculation Models and Methods

Results and Discussion

Conclusions