β-SnS/GaSe heterostructure: a promising solar-driven photocatalyst with low carrier recombination for overall water splitting

Abstract

Various two-dimensional (2D) materials have been well investigated as promising high-efficiency photocatalysts for solar-driven water splitting, while the high carrier recombination greatly hinders their practical application. One effective route to solve this issue is to rationally design type-II heterostructures with low carrier recombination based on 2D materials. Here, by performing extensive density functional theory calculations combined with non-adiabatic molecular dynamics simulations, we propose a β-SnS/GaSe heterostructure through constructing group-III and -IV monochalcogenides as a potential type-II photocatalyst for overall water splitting. Our results clearly show that the interlayer interaction between the β-SnS and GaSe monolayers in the heterostructure creates a relatively large built-in electric field and strong non-adiabatic coupling, which accelerate the separation of photogenerated carriers within sub-picoseconds. At the same time, the photogenerated carrier recombination occurs over a relatively long time scale, implying that the separated electrons and holes with strong redox capacity could effectively participate in water oxidation and reduction reactions on the GaSe and β-SnS monolayers, respectively. Meanwhile, the β-SnS/GaSe heterostructure exhibits strong optical absorption in the visible and ultraviolet ranges of the solar spectrum, and the sharp exciton peaks in visible-light regions are known as the interlayer, intralayer, or mixed-type bright excitons.