Electronic Properties of Vanadium‐Doped TiO 2

The electronic properties of vanadium‐doped rutile TiO 2 are investigated theoretically with a Hartree–Fock/DFT hybrid approach. The most common oxidation states (V 2+ , V 3+ , V 4+ , and V 5+ ) in different spin states are investigated and their relative stability is calculated. The most stable spin states are quartet, quintet, doublet, and singlet for V 2+ , V 3+ , V 4+ , and V 5+ doping, respectively. By comparing the formation energy with respect to the parent oxides and gas‐phase oxygen (Δ E ), we conclude that V 4+ (Δ E =145.3 kJ mol −1 ) is the most likely oxidation state for vanadium doping with the possibility of V 5+ doping (Δ E =283.5 kJ mol −1 ). The energetic and electronic properties are converged with dopant concentrations in the range of 0.9 to 3.2 %, which is within the experimentally accessible range. The investigation of electronic properties shows that V 4+ doping creates both occupied and unoccupied vanadium states in the band gap and V 5+ doping creates unoccupied states at the bottom of the conduction band. In both cases there is a significant reduction of the band gap by 0.65 to 0.75 eV compared to that of undoped rutile TiO 2 .