First principles study of photoelectrochemical water splitting in monolayer Sn2S2P4 with high solar-to-hydrogen efficiency

Exploring stable photocatalysts with superior optical absorption and high energy conversion efficiency is the key to water splitting. By means of the first-principles calculations, we report a ternary Sn2S2P4 monolayer with excellent stabilities. Remarkably, the material presents an indirect bandgap of 1.77 eV with the band edge perfectly crossing the redox potential of water. Monolayer Sn2S2P4 exhibits noticeable optical absorption and photocurrent density in the visible range and has adequate driving forces to trigger overall water splitting. Anisotropic and high carrier mobility facilitate the fast transport of photogenerated carriers. Moreover, a solar-to-hydrogen efficiency that reaches as high as 17.51% is theoretically predicted, thereby indicating that the Sn2S2P4 monolayer is a promising candidate for overall photocatalytic water splitting.