MoS₂-based two-dimensional (2D) heterostructure photocatalysts have attracted increasing attention due to their prominent photocatalytic performance, but still suffer from weak visible light absorption and low solar-to-hydrogen conversion efficiency. Herein, we comprehensively investigate the structural and electronic properties of 2D MoS₂/SnS heterostructure using first-principles calculations. It is found that the MoS₂/SnS heterostructure is a stable interface and forms a type-II heterojunction, which definitely facilitates the spatial separation and migration of photoexcited electron-hole pairs under light irradiation. More importantly, a relatively small band gap (roughly 0.29 eV) enables its light absorption spectrum to cover the entire visible light region. Interestingly, the Mo atoms in the MoS₂/SnS heterostructure would turn into catalytic active sites. As a result, constructing heterostructure of MoS₂ with SnS improves light absorption, accelerates the separation of electron-hole pairs, and activates the Mo atom at the basal plane, all of which could be beneficial to the photocatalytic activity. These results provide monolayer MoS₂-based heterojunction photocatalysts and insightful understanding of their physical mechanism.

基于MoS ₂的二维（2D）异质结构光催化剂由于其突出的光催化性能而引起了越来越多的关注，但仍遭受可见光吸收弱和太阳能到氢的转化效率低的问题。本文中，我们使用第一性原理全面研究了二维MoS ₂ / SnS异质结构的结构和电子性质。发现MoS ₂/ SnS异质结构是一个稳定的界面，并形成II型异质结，这无疑促进了光激发下光激发电子-空穴对的空间分离和迁移。更重要的是，相对小的带隙（大约0.29 eV）使它的光吸收光谱覆盖整个可见光区域。有趣的是，MoS ₂ / SnS异质结构中的Mo原子会变成催化活性位。结果，用SnS构造MoS _2的异质结构改善了光吸收，加速了电子-空穴对的分离，并激活了基面上的Mo原子，所有这些都可能有利于光催化活性。这些结果提供了单层MoS ₂异质结光催化剂及其对物理机理的深刻理解。