Synergistic Effects in La/N Codoped TiO2 Anatase (101) Surface Correlated with Enhanced Visible-Light Photocatalytic Activity

摘要

The interaction between implanted La,substitutional N,and an oxygen vacancy at TiO2 anatase (101) surface has been investigated by means of first-principles density function theory calculations to investigate the origin of enhanced visible-light photocatalytic activity of La/N-codoped anatase observed in experiments.Our calculations suggest that both the adsorptive and substitutional La-doped TiO2 anatase (101) surfaces are probably defective configurations in experiments.The h-Cave-adsorbed La doping decreases the formation energy for the substitutional N implantation and vice versa,while the charge compensation effects do not take effect between the adsorptive La and substitutional N dopants,resulting in some partially occupied states in the band gap acting as traps of the photoexcited electrons.The Tisc-substituted La doping decreases the energy required for the substitutional N implantation,and the substitutional La and N codopmg promotes the formation of an oxygen vacancy,which migrates from the Osb-3c site at the inner layer toward the surface Or,site.For the substitutional La/N-codoped (Ti5c_Oc-down) surface,the charge compensation between the substitutional La and substitutional N leads to the formation of two isolated occupied Ns-O π* impurity levels in the gap,while the excitation energy from the higher impurity level to the CBM decreases by about 0.89 eV.After further considering an oxygen vacancy on the Ti (s)e_O3c-down surface,the two electrons on the double donor levels (Ob vacancy) passivate the same amount of holes on the acceptor levels (substitutional La and N),forming the acceptor-donor-acceptor compensation pair,which provides a reasonable mechanism for the enhanced visible-light photocatalytic activity of La/N codoped TiO2 anatase.This knowledge may aid the further design and construction of new effective visible-light photocatalysts.