二维层状WS2/ZnO范德华异质结光催化剂的设计与理论研究

Design and Theoretical Study of Two-Dimensional Layered WS2/ZnO Van der Waals Heterostructure Photocatalyst

摘要:

范德华异质结（vdWH）的构建是一种提高二维材料性能的有效途径，借助第一性原理计算方法系统地研究了WS₂/ZnO vdWH的晶体结构及其电子、光催化和光学性质。计算结果表明，二维WS₂/ZnO vdWH具有II型能带排列特征，能有效分离光生载流子，提升载流子分离效率。由于电子会自发从WS₂转移到ZnO单层，WS₂/ZnO vdWH层间会形成内建电场，有效抑制光激发载流子的复合。与WS₂和ZnO两个单层相比，WS₂/ZnO vdWH的光学吸收系数在可见光区明显提高，数量级可达10⁴ cm^-1，具有增强的太阳能利用效率。通过能带排列计算发现，酸性条件比中性或碱性条件更利于WS₂/ZnO vdWH的光催化水解反应。此外，还探究了机械应变对WS₂/ZnO vdWH电子和光催化性质的影响规律，发现施加双轴拉伸应变可以调控WS₂/ZnO vdWH的II型异质结转变为I型异质结，有望应用于光电器件领域。上述结果表明，WS₂/ZnO vdWH是一种极具应用潜力的分解水光催化剂，计算结果可以为WS₂/ZnO vdWH的设计和制备提供理论指导和科学依据。

Abstract:

The construction of van der Waals heterostructure （vdWH） is an effective channel to improve the performance of two-dimensional materials. In this paper， the crystal structure of WS₂/ZnO vdWH and its electronic， photocatalytic， and optical properties are systematically investigated based on the first-principles calculation. The calculation results show that the two-dimensional WS₂/ZnO vdWH possesses type-Ⅱ band alignment， which can effectively separate photogenerated carriers and improve carrier separation efficiency. Due to the spontaneous transfer of electrons from WS₂ to the ZnO monolayer， a built-in electric field will be formed between the WS₂/ZnO vdWH layers， which can effectively inhibit photoexcited carrier recombination. Compared with the two monolayers of WS₂ and ZnO， the optical absorption coefficient of WS₂/ZnO vdWH is significantly improved in the visible light range， with an order of magnitude of 10⁴ cm^-1， showing that the heterostructure has enhanced solar energy utilization efficiency. According to the energy band alignment calculation， the acidic condition is more favorable for the photocatalytic hydrolysis of WS₂/ZnO vdWH than neutral or alkaline conditions. Additionally， the effect of mechanical strain on the electronic and photocatalytic properties of WS₂/ZnO vdWH is also explored. It is found that the application of biaxial tensile strain can regulate the transformation of type II heterojunction of WS₂/ZnO vdWH into type I heterojunction， which is expected to be applied in the field of optoelectronic devices. The above results show that WS₂/ZnO vdWH is a photocatalyst with great application potential for water splitting. The calculation results in this paper can provide theoretical guidance and a scientific basis for the design and preparation of WS₂/ZnO vdWH.