First principles study of Janus WSeTe monolayer and its application in photocatalytic water splitting

By employing the state-of-the-art density functional theory method, we demonstrate that Janus WSeTe monolayer exhibits promising photocatalytic properties for solar water splitting. The results show that the monolayer possesses thermodynamic stability, suitable bandgap (∼1.89 eV), low excitons binding energy (∼0.19 eV) together with high hole mobility (∼10³cm²V^-1s^-1). Notably, the results suggest that the oxygen evolution reaction can undergo spontaneously without any sacrificial reagents. In contrast, the overpotential of hydrogen evolution reaction can partially be overcome by the external potential under solar light irradiation. Furthermore, the intrinsic electric field induced by the symmetry breaking along the perpendicular direction of Janus WSeTe monolayer not only suppresses the electron-hole recombination but also contributes to the solar-to-hydrogen efficiency, which is calculated to be ∼19%. These characteristics make the Janus WSeTe monolayer to be a promising candidate for solar water splitting.