SnP₂S₆ monolayer: a promising 2D semiconductor for photocatalytic water splitting

By performing first principles calculations, we predict a new two-dimensional semiconductor, namely the SnP₂S₆ monolayer as a potential photocatalyst for solar water splitting. The exfoliation of the SnP₂S₆ monolayer from the experimentally-known layered bulk crystal is feasible by overcoming a small cleavage energy of 0.24 J m^-2. The SnP₂S₆ monolayer is a stable semiconductor with an indirect band gap of 2.23 eV, which can be effectively tuned by applying an in-plane biaxial strain. In particular, an indirect-to-direct band gap transition can be achieved under compressive strain. The band edge alignments of the monolayer match well with the water redox potentials. The carrier mobility of the SnP₂S₆ monolayer is as high as 143.12 and 148.48 cm² V^-1 s^-1 for holes and electrons, respectively. These extraordinary electronic properties as well as the good light harvesting performance render the SnP₂S₆ monolayer a good candidate for electronics and a promising photocatalyst to split water.