First-principles study on MoSSe/ GaTe van der Waals heterostructures: A promising water-splitting photocatalyst

•Two MoSSe/GaTe heterojunctions have been constructed on the basis of monolayer 2D materials GaTe and MoSSe.•The band gap values of the two heterostructures are calculated to be 1.081 and 1.307 eV, respectively.•The presence of the built-in electric field and the electrostatic potential difference results in MoSSe/GaTe crossing the redox potential of water at different surfaces, respectively. Photocatalytic water splitting using semiconductor electrocatalysts in photoelectrochemical cells is an appealing approach to converting sunlight and water into clean and renewable hydrogen fuel. MoSSe/GaTe der Waals heterojunctions has recently been suggested as a promising photocatalyst for water splitting. Depending on the stacking mode, the two type MoSSe/GaTe heterojunctions have moderate band gaps of 1.081 eV and 1.307 eV, significant visible absorption coefficients, and band-edge positions spanning the redox potential of water. Bader charge and differential charge density analyses show that the GaTe layer loses electrons and the MoSSe monolayer gains electrons, resulting in a built-in electric field pointing from the GaTe layer to the MoSSe layer. Moreover, the Gibbs free energy diagram indicates that solar energy can effectively drive water splitting on MoSSe/GaTe junction. The influence of the bi-axial strain and pH value of water are discussed. Therefore, the MoSSe/GaTe heterostructures are promising for applications in photocatalytic water decomposition.