School of Materials Science and Engineering , Anhui University of Technology , Maanshan 243002 , China.
State Key Laboratory of Photocatalysis on Energy and Environment , Fuzhou University , Fuzhou 350116 , China.
ACS Appl Mater Interfaces. 2018 Nov 14;10(45):39327-39335. doi: 10.1021/acsami.8b12178. Epub 2018 Nov 2.
Charge generation and separation are two key issues in developing a high-efficiency semiconductor for the visible-light-driven photocatalysis. Here, we use the layered perovskite-type wide-gap semiconductor LaTiO (LTO) as a model to systematically explore the synergistic effect of doping (with sulfur or nitrogen) and heterojunction (with graphitic CN) on improving visible light absorption and photoexcited charge separation by means of density functional theory calculations. It is found that the anion (N or S) doping into the LTO(010) surface can not only shift the optical absorption edge to the visible region, but also creates some partially occupied or unoccupied states in the band gap that would facilitate the formation of recombination centers. For the purpose of promoting electron-hole separation, the (N or S-doped) LTO(010) surfaces were hybridized with the monolayer g-CN. Interestingly, we found that the (S-doped) LTO/g-CN heterostructure forms a type-II heterojunction, with the valence band maximum residing in the (S-doped) LTO and the conduction band minimum in g-CN, respectively. This band alignment feature facilitates efficient electron-hole separation. Moreover, we found that the S-doped LTO/g-CN composite has a short interfacial distance (about 2.1 Å), implying that the interfacial interaction of this composite might be a chemical bond rather than a weak van der Walls interaction. The chemical bonding can enhance charge separation. Our theoretical findings provide design principles for optimizing the photocatalytic performance of the wide-gap photocatalysts and demonstrate that the S-doped LTO/g-CN composite would be a potential candidate for the photocatalysis of water splitting.
电荷的产生和分离是开发用于可见光驱动光催化的高效半导体的两个关键问题。在这里，我们使用层状钙钛矿型宽带隙半导体 LaTiO（LTO）作为模型，通过密度泛函理论计算系统地研究了掺杂（硫或氮）和异质结（与石墨相氮化碳）协同作用对提高可见光吸收和光激发电荷分离的影响。研究发现，阴离子（N 或 S）掺杂到 LTO（010）表面不仅可以将光吸收边缘移动到可见光区，而且还可以在带隙中形成一些部分占据或未占据的状态，这有利于形成复合中心。为了促进电子-空穴分离，（N 或 S 掺杂）LTO（010）表面与单层 g-CN 进行了杂化。有趣的是，我们发现（S 掺杂）LTO/g-CN 异质结构形成了 II 型异质结，价带最大值位于（S 掺杂）LTO 中，导带最小值位于 g-CN 中。这种能带排列特征有利于高效的电子-空穴分离。此外，我们发现 S 掺杂的 LTO/g-CN 复合材料具有较短的界面距离（约 2.1 Å），这意味着该复合材料的界面相互作用可能是化学键而不是较弱的范德华相互作用。化学键可以增强电荷分离。我们的理论研究结果为优化宽带隙光催化剂的光催化性能提供了设计原则，并表明 S 掺杂的 LTO/g-CN 复合材料可能是水分解光催化的潜在候选材料。
