Mo-doped TiO2 with 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 TiO2 have 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 TiO2 and 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 TiO2 particles 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 TiO2 lattice. The morphology of TiO2 particles 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.