Strain-Tunable Photocatalytic Performance in Two-Dimensional Janus In2S2X (X=Se,Te) Monolayer as Photocatalyst for CO2 Reduction

Strain engineering has been widely used in the study of two-dimensional semiconductors in recent years, because it can improve catalytic performance by changing the structural characteristics of materials. In this work, we systematically investigate the effects of biaxial strain on the electronic structure, band-edge positions, and optical absorption of perfect Janus In2S2X (X=Se, Te) particles and vacancy In2S2X (V-In2S2X). Biaxial strain enables In2S2X to achieve a transition between indirect and direct band gaps. Tensile strain reduces the band-edge potential of the conduction band minimum (CBM), but compressive strain increases it and then tends to stabilize the material. In V-In2S2X, the tensile strain makes the top bands of the bandgap overlap with the CBM and moves the bottom band of the bandgap down, reducing the bandgap, which makes the light absorption range redshift. Most importantly, we demonstrate that V-In2S2X obtains excellent photocatalytic CO2 reduction performance under 4 % tensile strain, broadening its practical applications in many fields.