| TiO2has been concerned extensively in the photocatalysis field ever since twoJapanese scientists who earliest found that TiO2have photocatalytic properties and reportedit in1972. It is generally recognized that the band gap of anatase TiO2is3.2eV, just absorbthe UV-light with the wavelength range in384nm, so its solar energy utilization is very low.Meanwhile, the optical electronic-hole pair were easy to composited, and the electronlifespan shorter. Ion-doping is the most effective approach to improve the photocatalyticactivity of anatase TiO2.The electronic structure of the rare earth elements is very special, itis easy to produce multi-electron configuration. Rare earth as dopants in the absorptionspectrum red-shift improve TiO2photocatalysis has enormous potential.The results of the study on photoelectric performance of TiO2doped with Pr haveopposite conclusions; two experimental results about red-shift and blue-shift are reportedin literatures. We set up the models of pure, Ti0.875Pr0.125O2and Ti0.9375Pr0.0625O2supercellsto calculate the energy, band gap width and absorption spectrum based on thefirst-principles to solve this conflict. Calculations results indicate that under the conditionof Pr doping there is a red-shift in the absorption spectrum, absorption strengthenhancement. With the concentrations of Pr increased, the band gap narrowed and thephotocatalysis more effectiveThe trend of the donor’s movements at the shallow level of nonmetal ion and rareearth ion codoping anatase TiO2is different from it in nonmetallic and transition metaldoping systems. But the relevant theoretical calculation rarely reported. Therefore, pure,TiO1.9375N0.0625, Ti0.9375Ce0.0625O2and Ti0.9375Ce0.0625O1.9375N0.0625supercell models wereestablished based on the first-principles plane wave ultra-soft pseudo potential method ofdensity function theory, geometry optimization and energy calculation of all models.Results indicate that compare with the pure TiO2, the band gap of the two doping systemsare narrowed. Synergies in donor and acceptor of the codoping systems improvement ofthe photocatalytic activity of TiO2.Inaddition, the impurity energy levels are very effectivefor the separation of photoexcited electron–hole pair and longer the electron lifespan. Theresults show that the trend of the donor’s movements at the shallow level of rare earth ion Ce and nonmetal ion N codoped anatase TiO2is not obvious. It is is different fromnonmetallic and transition metal doping systems.This is due to its very thick shell,resulting in shielding effect of the outer layer of the ce-4f.Due to Ce-(C,N) respectively codoping anatase TiO2first principles of the seriesresearch is rarely reported. Therefore, based on the previous research, theTi0.9375Ce0.0625O1.9375C0.0625and TiO1.9375C0.0625supercell models were established, thenanalysis of the structural changes and photocatalytic performance of the doping TiO2systems on micromechanism. Compare to crystal structure, electronic structure andabsorption spectrum in two codoping systems. Research found that the two doping systemsboth have the advantages which the single doping systems didn’t have. With the two atomscodoped, the absorption spectrum red-shift is more significant by synergy. The synergiesare also very effective for the separation of photo generated electron–hole pairs andimprove the lifespan of electron–hole pairs. At the same time，we found that in the Ce-Ncodoping systems the formation energy and total energy are lower than it in Ce-C codopingsystems, so it is easy for ions doping and the doping systems are more stable. But the bandgap width in Ce-C codoping systems is smaller than it in Ce-N codoping systems; theabsorption spectrum red-shift is more significant. Ce-C codoped anatase TiO2moreadvantageous to improve the photocatalytic performance. |
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