Abstract
The spin or nonspin state of electrons in W-doped anatase TiO2 is very difficult to judge experimentally because of characterization method limitations. Hence, the effect on the microscopic mechanism underlying the visible-light effect of W-doped anatase TiO2 through the consideration of electronic spin or no-spin states is still unknown. To solve this problem, we establish supercell models of W-doped anatase TiO2 at different concentrations, followed by geometry optimization and energy calculation based on the first-principle planewave norm conserving pseudo-potential method of the density functional theory. Calculation results showed that under the condition of nonspin the doping concentration of W becomes heavier, the formation energy becomes greater, and doping becomes more difficult. Meanwhile, the total energy increases, the covalent weakens and ionic bonds strengthens, the stability of the W-doped anatase TiO2 decreases, the band gap increases, and the blue-shift becomes more significant with the increase of W doping concentration. However, under the condition of spin, after the band gap correction by the GGA+U method, it is found that the semimetal diluted magnetic semiconductors can be formed by heavy W-doped anatase TiO2. Especially, a conduction electron polarizability of as high as near 100% has been found for the first time in high concentration W-doped anatase TiO2. It will be able to be a promising new type of dilute magnetic semiconductor. And the heavy W-doped anatase TiO2 make the band gap becomes narrower and absorption spectrum red-shift.
Highlights
In recent years, the stable physical and chemical properties and good photocatalytic performance of anatase TiO2 have caused it to attract increased attention in the field of photocatalysis [1,2,3,4,5,6]
Choi et al [7] studied the effect of 21 kinds of transition metals on the photocatalysis of anatase TiO2 and the results showed that Fe3+, Mo5+, Ru3+, Os3+, Re5+, V4+, and Rh3+ single doping can improve the visible-light effect of TiO2
Yang et al [8] investigated the effect of W doping on the visible-light effect of anatase and rutile mixed phase, and their results indicated that, when the doping weight fraction percentage of W is within the range of 1.5 wt%–10 wt%, the absorption spectrum of anatase and rutile mixed phase has a red-shift, and when the doping weight fraction percentage is 3wt%, the band gap is the narrowest, the red-shift reaches the most significant level
Summary
The stable physical and chemical properties and good photocatalytic performance of anatase TiO2 have caused it to attract increased attention in the field of photocatalysis [1,2,3,4,5,6]. The calculated results revealed that the band gap becomes narrower because of W and 2N single/co-doped in anatase TiO2 under the situation of spin and the absorption spectrum had a red-shift. Under the condition of non-spin, Fig 3A–3D are band structures of pure and W-doped anatase TiO2 (in this paper, all the Fermi levels have been specified to be 0 eV).
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