Effects of Nonmetal Doping on Electronic Structures and Optical Property of Anatase TiO2 from First-Principles Calculations

摘要:

采用基于密度泛函理论超软赝势平面波方法的第一性原理计算了纯锐钛相TiO2和非金属(B, C, N, F, P, S, Cl)掺杂体系的晶体结构、电子结构和光学性质。计算结果表明，非金属掺杂后由于晶格常数、键长、原子电荷分布的变化导致TiO2的八面体偶极矩增大，这对光生电子-空穴对的分离是十分有利的。由掺杂物的p电子态与O的2p电子态、Ti的3d电子杂化而形成的杂质能级的存在使大多数掺杂体系的带隙减小，从而使TiO2的基本吸收带边红移到可见光区。根据理论结果，系统分析和比较了非金属对锐钛矿相TiO2电子结构和光学性质的掺杂效应，同时非金属掺杂对TiO2光催化材料在可见光激发下的作用也得到了分析。计算结果解释了部分非金属掺杂可以使锐钛矿相TiO2在可见光激发下具有较高光催化活性的原因。

Abstract:

The crystal structures, electronic structures and optical properties of pure and nonmetal (B, C, N, F, P, S and Cl) doping anatase TiO2 were calculated by the first-principles based on the density functional theory with the plane-wave ultrasoft pesudopotentials method. The calculated results show that the octahedral dipole moments of TiO2 are increased by nonmetal doping owing to the changes of lattice parameters, bond length and charges on atoms, which is very effective for the separation of photoexcited electron-hole pairs. Because the impurity energy levels are formed by hybridizing with dopants’ p states, O 2p states and Ti 3d states, most dopants could narrow the band gap, resulting in its fundamental absorption edge red-shift to visible-light region. According to the calculated results, the effects of nonmetal doping on electronic structure and optical properties of anatase TiO2 were analyzed and compared, and the roles of nonmetal atoms in TiO2 photocatalyst under visible-light irradiation were clarified. The calculated results could explain the reasons that some nonmetal-doped TiO2 have higher photocatalytic activity under visible-light irradiation.