Two dimensional MoSSe/BSe vdW heterostructures as potential photocatalysts for water splitting with high carrier mobilities

Production of hydrogen fuel from water splitting driven by solar energy is an effective technique to overcome the energy crisis and environmental problems in coming decades. To explore low cost and efficient photocatalysts is highly desired. In this work, we study the electronic, optical and photocatalytic properties of MoSSe/BSe (Model-1 and Model-2) vdW heterostructures by PBE and HSE06 functionals using first-principle calculations. The stabilities of these heterostructures are confirmed through phonon spectra and ab initio molecular dynamic simulations. The Model-1 and Model-2 heterostructures have indirect band gaps of 1.95 and 1.54 eV respectively by HSE06 hybrid functional. Interestingly, the transition from indirect to direct band gap occurs in Model-1 after including spin-orbit coupling effect. Remarkably, the high carrier mobilities are quantitatively explored by means of deformation potential theory. Furthermore, the transition from type-I to type-II band alignment happens at compressive strain in both Model-1 and Model-2, which effectively slows down the recombination of electron-hole pairs. Compared to the isolated monolayers, the MoSSe/BSe (Model-1 and Model-2) heterostructures harvest maximum portion of visible spectrum, revealing the outstanding paybacks of high efficiency utilization of solar spectrum. Most intriguingly, the band edges of MoSSe/BSe vdW heterostructures meet the redox potential requirements for water splitting. Our results will be valuable for easing the investigation and applications of MoSSe/BSe heterostructures for optoelectronics and photocatalytic water splitting.