Zhang Junying, Dang Wenqiang, Ao Zhimin, Cushing Scott K, Wu Nianqiang
Department of Physics, Beihang University, Beijing 100191, China.
Phys Chem Chem Phys. 2015 Apr 14;17(14):8994-9000. doi: 10.1039/c5cp00157a. Epub 2015 Mar 9.
In order to reveal the origin of enhanced photocatalytic activity of N-doped La2Ti2O7 in both the visible light and ultraviolet light regions, its electronic structure has been studied using spin-polarized conventional density functional theory (DFT) and the Heyd-Scuseria-Ernzerhof (HSE06) hybrid approach. The results show that the deep localized states are formed in the forbidden band when nitrogen solely substitutes for oxygen. Introducing the interstitial Ti atom into the N-doped La2Ti2O7 photocatalyst still causes the formation of a localized energy state. Two nitrogen substitutions co-exist stably with one oxygen vacancy, creating a continuum energy band just above the valence band maximum. The formation of a continuum band instead of mid-gap states can extend the light absorption to the visible light region without increasing the charge recombination, explaining the enhanced visible light performance without deteriorating the ultraviolet light photocatalytic activity.
为了揭示氮掺杂的La2Ti2O7在可见光和紫外光区域光催化活性增强的起源，采用自旋极化传统密度泛函理论（DFT）和Heyd-Scuseria-Ernzerhof（HSE06）杂化方法对其电子结构进行了研究。结果表明，当氮单独取代氧时，在禁带中形成了深局域态。将间隙Ti原子引入氮掺杂的La2Ti2O7光催化剂中仍然会导致局域能态的形成。两个氮取代与一个氧空位稳定共存，在价带最大值上方形成一个连续能带。连续能带的形成而非带隙中间态的形成可以将光吸收扩展到可见光区域而不增加电荷复合，这解释了可见光性能增强而紫外光光催化活性不降低的原因。
