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Geometric and electronic structures of the boron-doped photocatalyst TiO2

Boron-doped anatase TiO2 has been shown to be a much more efficient and stable photocatalyst than the pristine TiO2. We employed the LDA-supercell approach to calculate the geometry and electronic structures of the doped systems, in order to reveal the microscopic mechanism of how photocatalytic efficiency is improved by boron doping. It is found that the boron atom tends to either replace an oxygen atom or sits in the interstitial position. It is highly unlikely for the boron atom to replace Ti. The density of states analysis shows that for oxygen-substituted doping the boron atom is strongly bonded to two oxygen atoms as well as to two Ti atoms, which results in new midgap states, and eventually the absorption edge is red-shifted and the photocatalytic efficiency is enhanced.