氮铁共掺锐钛矿相TiO2电子结构和光学性质的第一性原理研究

本文采用基于密度泛函理论的平面波超软赝势方法研究了N,Fe共掺杂TiO₂的晶体结构、电子结构和光学性质.研究表明,N,Fe共掺杂TiO₂的晶格体积、原子间的键长及原子的电荷量发生变化,导致晶体中产生八面体偶极矩,并因此光生电子-空穴对有效分离,提高TiO₂的光催化活性;N,Fe共掺杂同时在导带底和价带顶形成了杂质能级,使TiO₂的禁带宽度变窄,光吸收带边红移到可见光区,这些杂质能级可以降低光生载流子的复合概率,提高Ti

First-principles study on electronic structure and optical properties of anatase Ti02 codoped with nitrogen and iron

The crystal structure, electronic structure and optical properties of nitrogen and iron codoped anatase TiO₂ were studied by using the plane-wave ultrasoft pesudopotentials method based on density functional theory. The calculated results show that the octahedral dipole moments in nitrogen and iron codoped TiO₂ increase due to the changes in lattice parameters, bond length and charge of atoms, which is very effective for the separation of photoexcited electron-hole pairs and the improvement of the photocatalytic activity of TiO₂. Some impurity energy levels of codoped TiO₂ are below the conduction band minimum, and others are above the valence band maximum. The distance between them is narrowed, which results in the redshift of the optical absorption edges to visible-light region. These impurity energy levels can reduce the recombination rate of photoexcited carriers and improve the photocatalytic efficiency of TiO₂. Compared with that of Fe doped TiO₂, for the codoped TiO₂, the density of states peak of impurity energy levels above the valence band maximum increase apparently, which increases the electronic transition probability from the impurity energy levels to the conduction band, and improves the solar energy utilization. If the impurity level is not taken into account, compared with that of pure TiO₂, the CB edge position and the VB edge position of codoped TiO₂ is only slightly changed, it means that the strong redox capacity of codoping photocatalysts is still excellent.