氧缺陷型金红石相TiO2-x(x=0~0.5)光电性能理论研究

Theory Research on the Photoelectric Properties of Oxygen-deficient Rutile TiO2-x(x=0~0.5)

摘要:

本文采用密度泛函理论方法,研究氧缺陷型金红石相TiO_2-x(x=0~0.5)光催化剂晶体结构、能带结构以及光电行为。计算结果表明,金红石型TiO₂引入氧缺陷后,在带隙中间形成不同程度的缺陷能级,由Ti 3d和O 2p组成,大大降低了电子从价带跃迁到导带所需要的能量,使TiO_2-x的吸收边红移,增强了可见光响应,有利于提高可见光催化活性。随着氧缺陷浓度θ由1.39%升高到25%,TiO_2-x的带隙先减小后增大,当θ=6.25%时,禁带宽带减小至1.46 eV。综合紫外-可见吸收光谱结果,6.25%为最佳氧缺陷浓度,电子在晶体中迁移率大,对可见光的吸收强度大,有利于提高TiO₂的光催化性能。

Abstract:

A density functional theory method has been employed to investigate the crystal structures, band structures and photoelectric properties of oxygen-deficient rutile TiO_2-x(x=0~0.5). Defected states composed of Ti 3d and O 2p appear in the band gap owing to the introduction of oxygen vacancies. These defected states reduce the energy for electrons jumping from valence bands to conduction bands, so the absorption edge of TiO_2-x has a red shift, and the absorption intensity of visible light is enhanced, which is beneficial to the photocatalytic activity under visible light. The band gap first decreases and then increases with the increasing of oxygen vacancy concentration (θ) from 1.39% to 25%. When θ=6.25%, the band gap is the smallest which is 1.46 eV. Moreover, according to the UV-vis absorption spectra, it could be confirmed that θ=6.25% is the best oxygen vacancy concentration to improve the photocatalytic activity of TiO₂ because of the large electron mobility and the highest absorption ability of visible light.