Tailoring the photocatalytic properties of anatase TiO2 by B-TM (TM = Pt, Ta, V) co-doping

In order to provide insight into the influence of co-doping with boron (B) and transition metals (TM = Pt, Ta, V) on the photoactivity of anatase TiO2, the electronic, structural and optical characteristics of the mentioned co-doped systems were studied using density functional theory calculations and the modified Becke-Johnson exchange potential. For each transition metal two cases were considered, with B atom either replacing O atom (B-substitutional) or imbedding interstitially (B-interstitial) into TiO2 lattice. The calculations showed that the co-doping is more favorable for the B-interstitial systems than for the B-substitutional ones and under the O-rich conditions. For the B-substitutional cases a slight decrease of the band gap is observed. In contrast, the results obtained for the B-interstitial systems exhibited no band gap narrowing. However, in these systems, the occurrence of localized states within the band gap is noticed, which could improve visible light absorption through a two-step optical transition.