Two-dimensional germanium monochalcogenide photocatalyst for water splitting under ultraviolet, visible to near-infrared light.

Full utilization of solar energy to split water into hydrogen and oxygen is an efficient way to solve the current energy problem. Graphene-like germanium monochalcogenides (GeS or GeSe) are proposed here as efficient photocatalysts for water splitting under a broad range from ultraviolet, visible to near-infrared light dependent on their thickness. Compared to traditional photocatalysts, GeS and GeSe possess a large intrinsic dipole and introduce an internal electric field directing from Ge surface to S/Se surface, which causes notable band bending. The band bending means they possess favorable band positions located outside the reduction potential and oxidation potential of water, overcoming the restriction of their band gaps. Moreover, multilayer GeS and GeSe further provide a good separation of electrons and holes, which effectively reduces the probability of their recombination and ensures photocatalytic activity with high efficiency.