Mo-doped TiO₂with enhanced visible light photocatalytic activity: A combined experimental and theoretical study

In this paper, the effects of Mo doping on the geometrical, electronic, optical, and photocatalytic properties of TiO₂have been investigated theoretically and experimentally. The density functional theory based calculations show that Mo doping creates impurity states (Mo 4d) below the conduction band of TiO₂and the Fermi level is pinned inside the conduction band verifying n-type doping nature of the Mo in TiO₂, which enhances its visible light absorption. Anatase TiO₂particles with Mo contents of 0.08, 0.1, 0.5, 1.0, 1.5 and, 2.0 at % were synthesized by hydrothermal method without any post heat treatment for crystallization. Experiment results show that Mo ions have been successfully doped into the TiO₂lattice. The morphology of TiO₂particles is nearly spherical and the grain size is uniformly distributed as about 10 nm. Synthesized sample with 0.1 at.% Mo doping concentration shows the best visible light photocatalytic activity due to the reduced band gap and improved electron-hole pairs separation. However, the photocatalytic activity of the sample with 2.0 at.% Mo is relatively low although its visible light absorption is the best among the samples. The enhanced recombination of electron-hole pairs caused by the excessive Mo doping concentration may account for it.