XYZ2 (X/Y = Ge, Pb, Sn; Z = Se, S, Te) two-dimensional Janus monolayers for photocatalytic water splitting: A first-principles study

Two-dimensional (2D) Janus materials have received growing recognition due to their promising applications in areas such as optoelectronic devices and photocatalytic water splitting. A novel Janus monolayer of metal chalcogenides XYZ2 (X/Y= Ge, Pb, Sn; Z = Se, S, Te) was examined by using first-principles calculations, and eight stable semiconductor types were identified then further studied focusing on their mechanical properties, electronic structure, optical properties, solar-to-hydrogen efficiency (eta STH), and Gibbs free energy. They possess suitable band gaps and well-aligned band edge positions, along with excellent visible light absorption capabilities. Specifically, GePbSe2, SnPbS2, and GePbTe2 exhibited high electron mobility, with eta STH over 20 %; Gibbs free-energy change further shows that these materials can spontaneously drive oxygen and hydrogen evolution reactions under illumination. These results point to a viable option for overall water splitting photocatalysts.