EXPERIMENTAL AND THEORETICAL STUDIES ON THE OPTICAL PROPERTIES OF N - DOPED TiO 2 - / SUB - COPPER

The TiO2 based semiconductor materialswere given much attention because of their superior performance, but the large band gap, quantum efficiency and low defects ofTiO2,which limite its wide application in practice. Therefore, it has great practical significance in improving its catalytic activity under visible light by doping TiO2.In this paper, N,Ag, V single-doped and Ag-N, V-N co-doped TiO2 powder catalysts were prepared respectively by sol-gol method in the experiment. The crystal structure, morphology, optical catalytic properties were characterized using XRD, SEM and UV-Vis.The effect factors,such as the doping elements and concentration, the calcination temperature and so on had been studied, and the difference between single element doped and co-doped TiO2 had been investigated as well. Further more,the microscopic mechanism of the optical properties of the N, Ag, V single-doped and Ag-N, V-N co-doped TiO2 had been further studying by the first-principles CASTP packages. The results have shown as below :The photocatalytic activity of N-doped TiO2 samples increased at first and then decreased with the increased doping concentration. It had highestphotocatalytic avtivity of N-doped Ti O2 at the doping concentration of 1:1(the atomic percentage of N and Ti). N-doped TiO2 sample had only single anatase phase and its photocatalytic properties was alsoincreased as the calcination temperature rised from300℃ to500℃,but decreasedat 600℃ as part anatase TiO2 transformed into rutile phase.The experiment results of different concentrations of Ag, V single-doped TiO2 powdersindicate thatthe lattice defects werecaused andthe grain sizewas also decreased. The photocatalytic activity of Ag-doped TiO2,V-doped TiO2 increased at first and then decreased with the increaseddoping concentration. The optimum percentages of dopant for Ag、V doped TiO2 photocatalystcalcined at 500℃were 1.79at% and 0.1at% respectively prepared under the experimental conditions.The photocatalytic performance of pure TiO2, N-doped TiO2, Ag-doped TiO2 and Ag-N co-doped TiO2 powder catalysts at the N, Agoptimum doping percentage and calcination temperature had been studied. The experiment results show thatAg-N co-doped TiO2 samples had ony anatase phase. Compared with N, Ag, V single-doping, co-doped systems redshift of the most obvious and the band gap of the smallest. Ag-Nco-doped samples showed higher photocalytic activity as Ag and Nplayed a synergistic role in the improvement of the photocatalytic properties of TiO2.The calculation results confirmed that the lattice defects caused and impurity levels introduced in the band gap, and the band gap also decreased because of doping. Compared with single-dopingsystem, it could be found photocatalytic properties of TiO2 more significantly in co-doped systems. The results of computation and theory were comparable with those obtained from experiment.The photocatalytic performance of pure Ti O2, N-doped TiO2, V-doped TiO2 and V-N co-doped TiO2 powder catalysts at the N, Voptimum doping percentage and calcination temperature had been studied. It shows that co-doped TiO2 samples had ony anatase phase and the particle size drcreased significantly. Compared with N, V single-doping, co-doped systems redshift of the most obvious and the band gap of the smallest. V-N co-doped samples showed higher photocalytic activity due to their synergistic codoping effect. The calculation results confirmed that the band gap reduced after N doped TiO2. V doping introduced V-3d statesunder CBM, which couldreducethe e-/h+ recombination rate.And some new impurity states appeard in band gapof V-N co-doped TiO2.Compared with single-dopingsystem, it had higher photocatalytic activity of TiO2 in co-doped system due to the reduced band gap and the e-/h+ recombination rate. The theoretical calculation provided reasonable explanationfor those obtained from experiment.