CdS/FeP复合光催化材料界面结构与性质的理论研究（英文）

Theoretical Study of the Interfacial Structure and Properties of a CdS/FeP Composite Photocatalyst

构建同质异相或异质结构是提高光催化材料性能的有效途径之一,尤其是对于CdS这类具有光腐蚀的材料,这种方法还能起到提高光催化材料稳定性的作用。因此目前制备CdS基复合光催化材料得到了广泛的研究,但是目前对其中的一些基本问题和关键因素仍需要进一步探讨和解释。本文采用第一性原理方法对CdS/FeP复合光催化材料中异质结构的界面微观结构和性质进行深入研究。计算结果表明,由于在界面上部分悬挂键被饱和,界面模型呈现出与体相或表面模型不同的电子结构特征,并且有界面态的存在。在CdS/FeP异质结构的界面处,CdS和FeP的能带都相对向下移动,而且FeP的能带(费米能级)插入到CdS的导带下方;同时在界面达到平衡态之后,异质结构的内建电场由FeP层指向CdS层,因而能够实现光生电子-空穴对在CdS/FeP界面处的空间有效分离,这对于光催化性能的增强极其有利。此外,构建CdS/FeP异质结构也能够进一步增强CdS在可见光区的光吸收。本文研究结果为构建具有异质结构的高效复合光催化材料提供了机理解释和理论支持。

An effective method for improving the performance of a photocatalyst is to construct a suitable hetero-/homo-structure. This strategy can also lead to improvements in the stability of the photocatalysts that suffer with photo-corrosion （such as CdS）. The preparation of CdS-based composite photocatalysts has therefore been widely studied. Unfortunately, however, some of the fundamental and more significant aspects of this strategy still need to be evaluated in greater detail. In this study, we have evaluated the interfacial microstructure and properties of a CdS/FeP composite photocatalyst with a hetero-structure using a series of the firstprinciples calculations. The results revealed that the electronic structure of the interface model exhibited different features compared with the bulk and surface models, because of the partially saturated dangling bonds. However, several obvious interfacial states were observed. At the interface of the CdS/FeP hetero-structure, the energy bands of CdS and FeP were relatively down-shifted, whereas the energy band of FeP was inserted below the conduction band of CdS. Furthermore, the direction of the built-in electric field of the hetero-structure projected out from the FeP layer towards the CdS layer under the equilibrium conditions. The photo-generated electron-hole pairs were therefore spatially separated by the CdS/FeP interface, which was favorable for improving the photocatalytic performance. The construction of a CdS/FeP hetero-structure can also lead to further improvements in the absorption properties of CdS in the visible-light region. The results of this study have provided mechanical explanations and theoretical support for the construction of highly efficient composite photocatalyst with hetero-structures.