Electronic, optical and photocatalytic water splitting properties of two-dimensional monolayers of Janus Cd2XY (X = S, Se; Y = Se, Te; X ≠ Y): A first-principles study

Abstract Two-dimensional Janus materials play a significant role in the advancement of optoelectronic devices and photocatalytic water splitting. In the present work, the stability, electronic structure, transfer properties, optical properties, and photocatalytic water-splitting properties of three Janus monolayers (Cd2SSe, Cd2STe, and Cd2SeTe) were investigated by using first-principles calculations. It is found that they are well-stabilized with a band gap Eg of 1.14, 1.49, and 2.32 eV (the photocatalytic water splitting threshold being 1.23 eV) respectively, all of which correspond to direct band gap semiconductors. They all demonstrate excellent electron mobility and hole mobility, along with high light absorption in the visible range. The band-edge potential of Cd2SSe crosses the potential for the redox reaction of water; Applying biaxial tensile strain enhances its light absorption efficiency and reduces the band gap, thereby increasing the performance of photocatalytic water splitting. Each step of the HER and OER reaction process with Cd2SSe as a catalyst can be carried out spontaneously under light conditions. The results indicate that the three Janus monolayers hold significant promise in next-generation optoelectronic devices and photocatalysts.