Multilayer films of indium tin oxide/TiO2 codoped with vanadium and nitrogen for efficient photocatalytic water splitting

TiO2 films codoped with V cations and N anions were synthesised by RF-magnetron sputtering. The incorporation of V and N in TiO2 lattice produces isolated energy levels near the conduction and valence bands, respectively, causing an effective narrowing of the band gap to 2.5 eV. Recombination of photo-charges was reduced by depositing multilayer films of indium tin oxide (ITO)/V-N-codoped TiO2 with different numbers of bilayers. In multilayer structure, the generated photoelectrons, travelling into TiO2 film of limited thickness, rapidly enter the space charge interface of the ITO/TiO2 films from where they are instantaneously injected into the ITO layer and then removed towards the cathode. The synergic effects created by band narrowing and enhanced charge separation by using codoping and multilayer structure strategy in TiO2 generate higher photocurrent for water splitting under visible light which definitely exceeds that obtained by doping TiO2 with a single, V or N, element.