Two-dimensional Janus X₂SSe (X = Al, Ga or In) monolayers: potential photocatalysts with low effective mass

Janus 2D materials with high-efficiency solar energy conversion possess fine photocatalytic properties, which are current research hotspots in the field of photocatalysis. Herein, Janus X₂SSe (X = Al, Ga or In) monolayers were proposed to explore their photocatalytic activities through first-principles calculation. The results demonstrated that the structures of Janus X₂SSe (X = Al, Ga or In) monolayers were both dynamically and thermodynamically stable and exhibited excellent semiconductor properties. Additionally, a low effective mass for the photogenerated electrons and holes was observed. However, the Janus Al₂SSe monolayer had an inappropriate band-edge potential, and the light-absorption edge corresponding to the maximum wavelength of the Janus Ga₂SSe monolayer was not wide enough, which did not meet the conditions for an effective photocatalyst. Amazingly, the Janus In₂SSe monolayer not only completely met the redox conditions for photocatalytic water decomposition but also presented visible-optical absorption with an absorption-band edge at 662 nm because of its indirect band gap of 1.52 eV, revealing its great application potential in photocatalysis. The above findings disclose the potential of the Janus In₂SSe monolayer as a high-performance photocatalyst.