Janus XYZ2 (X/Y = Al, Ga, and In; X ≠ Y; Z = S, Se, and Te) monolayers: Excellent photocatalysts for water splitting

Abstract

Two-dimensional (2D) Janus structures have attracted much attention due to the existence of built-in electric field. Here, we investigate photocatalytic properties of 2D Janus XYZ₂ (X/Y = Al, Ga, and In; X ≠ Y; Z = S, Se, and Te) monolayers. The results show that the bandgap satisfying water splitting in these structures reduce to (1.23 – Δφ) eV, where Δφ represents the work function difference of the Janus structures. Besides, the built-in electric field enhances the overpotential of hydrogen evolution reaction (HER), thus further increasing its reduction capability for water splitting. For example, AlInS₂ can achieve water splitting considering the built-in electric field, at pH = 0. Otherwise, the photocatalytic condition is not satisfied. Moreover, Janus AlGaS₂, AlGaSe₂, AlInS₂, AlInSe₂, and GaInS₂ monolayers satisfy water splitting in all acid-base solutions (pH = 0–14). All Janus XYZ₂ monolayers can absorb Ultraviolet (UV). The results reveal that 2D Janus XYZ₂ monolayers are remarkably excellent photocatalysts for water splitting.