Density Functional Theory Study On The Electronic Structure Of The Novel Semiconductor Photocatalysts

To explore the feasible strategies to improve the semiconductors’ photocatalytic activity,the geometric,electronic as well as some related properties of Zn2GeO4 with and without N/F doping,ZnIn2S4,and red and black phosphorus were thoroughly investigated by density functional theory(DFT)calculations.The main contents of this paper are listed as follows:.1.The results of pure,N-doped,F-doped,and N/F-codoped Zn2GeO4 indicates that the N/F codoped system is more stable than the monodoped systems.The effective mass of holes in the N-doped system is smaller.It’s obviously that F doping play some roles in nar:rowing the band gap inducing a significant extension of the optical absorption curve.In the N/F-codoped system,the valence band edge seems more dispersive which is convenient for the electronic transfer from VBM to CBM.This narrows down the band gap significantly and the optical absorption spectrum of N/F-codoped system red shift into the visible light region.2.The first-principles theory were performed to investigate the electronic structure and optical properties of ZnIn2S4 compared with ZnS.Our results indicate that the ZnS4,InS4 tetrahedrons and InS6 octahedrons are indispensable for the lower recombination rate of charge carriers.The In 5p and 5s states are the main component of the front molecular orbitals for ZnIn2S4,resulting in the narrowed band gap and strong responsibility for visible light irradation.the appropriate band edge position indicates its potential photocatalysis activity for water-spitting reactions.3.To examine the photocatalytic performances of red and black phosphorous,the electronic properties of the bulk and monolayer red phosphorous(rP),black phosphorous(bP)bulk and 1-3 layers nanosheet were investigated,respectively.Our results demonstrate that the red phosphorous bulk is an admirable semiconductor with narrow indirect band gap and strong visible-light response.While the monolayer red phosphorous is a direct semiconductor with increased separation efficiency of photogenerated charge carries.For the bulk black phosphorous,the band gap is small with light effective mass of photogenerated charge carriers.The band gap is increased with the redusced layers.ramaticlly.And the band gap of monolayer black P nanosheet is wide with admirable band edge position for water reduction and oxidization.The mobility and separation efficiency of the charge carriers is higher along the Y axis,which is favorable for the photocatalyst.So we can demodulate the electronic properties of red and black phosphorous by controling the number of layers to exploit their photocatalytic activity.