Ab initio study of two-dimensional silicon monochalcogenide on aluminum nitride heterobilayer for photocatalytic activity

The electronic, optical, and photocatalytic features of a newly proposed 2D material-based van der Waals heterobilayer, formed by vertically stacking monolayered SiS and AlN, have been investigated. The feasibility of utilizing this heterojunction as a potential photocatalyst for spontaneous water decomposition has been predicted by using the ab initio calculations. The findings reveal that the SiS@AlN heterobilayer can be stacked in four different patterns, resulting in a direct band gap ranging from 2.11 to 2.70 eV, as determined by HSE-06 calculations. The SiS@AlN composites exhibit appropriate band-edge locations for the oxidation and reduction reactions of water splitting. Moreover, the photocatalytic activity of SiS@AlN composites is significantly influenced by the electrolyte's pH. At equilibrium, the composite displays a direct Z-scheme band alignment, which facilitates the effective spatial separation of photo-excited charges and extends their lifetimes. Additionally, a significant built-in electric field is generated at the composite interface, further preventing the recombination of photo-excited electron-hole pairs. Furthermore, the hetero-bilayers exhibit better absorption of sunlight in both the visible and ultraviolet regions compared to individual 2D-SiS and 2D-AlN. These findings highlight the potential of the SiS@AlN hetero-bilayer for applications in solar water decomposition and optical device technologies.