Abstract
The electronic structures, formation energies, and band edge positions of anatase TiO2 doped with transition metals have been analyzed by ab initio band calculations based on the density functional theory with the planewave ultrasoft pseudopotential method. The model structures of transition metal-doped TiO2 were constructed by using the 24-atom 2 × 1 × 1 supercell of anatase TiO2 with one Ti atom replaced by a transition metal atom. The results indicate that most transition metal doping can narrow the band gap of TiO2, lead to the improvement in the photoreactivity of TiO2, and simultaneously maintain strong redox potential. Under O-rich growth condition, the preparation of Co-, Cr-, and Ni-doped TiO2 becomes relatively easy in the experiment due to their negative impurity formation energies, which suggests that these doping systems are easy to obtain and with good stability. The theoretical calculations could provide meaningful guides to develop more active photocatalysts with visible light response.
Highlights
The discovery of water photolysis on a TiO2 electrode by Fujishima and Honda in 1972 [1] has been recognized as a landmark event
As a wide band gap oxide semiconductor (Eg = 3.23 eV), anatase TiO2 can only show photocatalytic activity under UV light irradiation (λ < 387.5 nm) that accounts for only a small portion of solar energy, in contrast to visible light for a major part of solar energy
Structural optimization The optimized structures of transition metal-doped anatase TiO2 were calculated before the calculations of the electronic structures, which were performed to find the lattice parameters with the lowest energy
Summary
The discovery of water photolysis on a TiO2 electrode by Fujishima and Honda in 1972 [1] has been recognized as a landmark event. TiO2 has attracted extensive attention as an ideal photocatalytic material because of its excellent properties such as high activity, good stability, nontoxicity and low cost. It has been widely used in the fields of renewable energy and ecological environmental protection [2,3,4]. As a wide band gap oxide semiconductor (Eg = 3.23 eV), anatase TiO2 can only show photocatalytic activity under UV light irradiation (λ < 387.5 nm) that accounts for only a small portion of solar energy (approximately 5%), in contrast to visible light for a major part of solar energy (approximately 45%). Many efforts have been devoted to extending the spectral response of TiO2 to visible light, including energy band modulation by doping with elements [5,6,7,8,9,10,11], the construction of heterojunctions by combining TiO2
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