Constructing a new 2D Janus black phosphorus/SMoSe heterostructure for spontaneous wide-spectral-responsive photocatalytic overall water splitting

Janus MoSSe monolayer with built-in electric dipole, as another emerging two-dimensional (2D) material after MoS2, is predicted to be an ideal photocatalyst for overall water splitting. However, in spite of the excellent hydrogen evolution reaction (HER) activity of Se-surface, the extremely poor oxygen evolution reaction (OER) activity of S-surface hinders the achievement of photocatalytic overall water splitting. Herein, we construct a new 2D van der Waals heterostructure consisting of high-OER-active black phosphorus (BP) and Janus MoSSe monolayer, and demonstrate a new strategy of Janus BP/SMoSe heterostructure to achieve wide-spectral-responsive photocatalytic overall water splitting. The electronic structures and optical properties of two different heterostructures, BP/SMoSe and BP/SeMoS, are systematically investigated via first principles density, exhibiting a type-II band arrangement. Unlike BP/SeMoS, the BP/SMoSe heterostructure shows excellent optical properties, such as a large dielectric constant of 8.14 and a small optical absorption boundary of 0.10 eV. Furthermore, BP/SMoSe heterostructure possesses greater light absorption intensity and a broader light absorption range. It is found that the BP/SMoSe heterostructure exhibits proper band alignment and enhanced intrinsic dipole, which is favorable to obtain high electron-hole separation efficiency. This work provides a feasible strategy of 2D Janus BP/SMoSe heterostructure for approaching almost perfect overall water-splitting photocatalysis.