第一性原理计算Mo浓度对Mo掺杂BiVO_(4)光催化性能的影响

Effects of Mo concentration on photocatalytic activity of Mo-doped BiVO_(4)from first-principles calculations

本文利用基于密度泛函理论的第一性原理研究了不同浓度的Mo掺杂BiVO_(4)的V位的电子结构、光学性质和光催化性能.缺陷形成能的计算结果说明BiMo_(x)V_(1-x)O_(4)(x=0.0625,0.125,0.25)三种掺杂体系都是可以稳定存在的.电子结构计算结果表明:BiMo_(x)V_(1-x)O_(4)(x=0,0.0625,0.125,0.25)四种体系的带隙分别为2.123 eV,2.142 eV,2.160 eV和2.213 eV.掺杂BiVO_(4)体系的带隙值均大于本征BiVO_(4),且带隙随着Mo浓度的增加而增大.BiMo_(x)V_(1-x)O_(4)(x=0.0625,0.125,0.25)三种掺杂体系的能带结构全部向低能量区域移动,导致掺杂体系导带底越过费米能级,Mo掺杂BiVO_(4)后具有n型半导体特性.光学性质计算结果表明,本征BiVO_(4)和BiMo_(x)V_(1-x)O_(4)(x=0.0625,0.125,0.25)三种掺杂体系的介电常数分别为3.08,3.90,12.7和17.50,掺杂后的静介电常数都呈现增大的趋势.对于反射系数和介电函数虚部而言,掺杂BiVO_(4)体系在低能量区域内提升明显.对于吸收系数而言,在掺杂的三种体系中,Mo掺杂BiVO_(4)体系的光吸收系数对红外光的吸收提升明显.光催化性能计算结果表明,本征BiVO_(4)氧化H_(2)O生成O_(2)的能力最弱,BiMo_(0.25)V_(0.75)O_(4)氧化H_(2)O生成O_(2)的能力最强.

In this paper,the electronic structures,optical properties and photocatalytic performances of Mo doped into V-site of BiVO_(4)with different concentrations were investigated using the first nature principles based on density generalized function theory.The results of the defect formation energy calculations indicate that all three doping systems of BiMo_(x)V_(1-x)O_(4)(x=0.0625,0.125,0.25)are stable.The electronic structure calculations show that the band gaps of the four systems of BiMo_(x)V_(1-x)O_(4)(x=0,0.0625,0.125,0.25)are 2.123 eV,2.142 eV,2.160 eV and 2.213 eV,respectively.The band gap values of the doped BiVO_(4)system are all larger than that of the intrinsic BiVO_(4),and the band gap increases with the increase of Mo concentration.The energy band structures of the three doped systems BiMo_(x)V_(1-x)O_(4)(x=0.0625,0.125,0.25)are all shifted to the lower energy region,resulting in the doped system conduction band bottom crossing the Fermi energy level,and Mo doped BiVO_(4)has n-type semiconductor properties.Optical property calculations show that dielectric constants of the intrinsic BiVO_(4)and three doped systems BiMo_(x)V_(1-x)O_(4)(x=0.0625,0.125,0.25)are 3.08,3.90,12.7 and 17.50,respectively,and the static dielectric constants show an increasing trend after doping.The reflection coefficients and the imaginary parts of the dielectric functions for the three doped BiVO_(4)systems are significantly enhanced in the low-energy region,and the light absorption coefficients of three Mo-doped BiVO_(4)systems are significantly enhanced for infrared light.The photocatalytic performance calculations showed that the intrinsic BiVO_(4)oxidation of H_(2)O to O_(2)is the weakest and the BiMo_(0.25)V_(0.75)O_(4)oxidation of H_(2)O to O_(2)is the strongest.