Rashba Spin Splitting and Photocatalytic Activity in 2D Janus SbXBr (X = S, Se) Monolayers Based van der Waals Heterostructures

In this work, we have systematically studied the structural, Rashba spin splitting, and photocatalytic water splitting properties of two-dimensional (2D) Janus SbXBr (X = S, Se) monolayers (MLs) and their van der Waals (vdW) heterostructures (HSs) with different models and stacking. The Janus materials have emerged as a promising family of 2D materials for their applications in spintronics, optoelectronic devices, and photocatalytic water splitting, as they have exhibited two different surfaces that enable them to use for bifunctional properties. The asymmetry of atoms along the z-direction breaks the mirror symmetry and inversion symmetry. The inclusion of spin–orbit coupling (SOC) splits the energy band with opposite spins across the high symmetry point in the momentum space. The spin splitting in SbXBr (X = S, Se) MLs is confirmed as Rashba-type splitting, and it remained invariant in VdW HSs. The HSs were found to exhibit strong Rashba splitting strength. Moreover, we studied the band edge alignment for photocatalytic water splitting. In this work, we have observed that all HSs form Type-II band alignment that has an important role in a delay in the electron–hole charge recombination, leading to an enhanced photocatalytic reaction. In addition, the band edges of the HSs fulfill the criteria of the redox potentials of the hydrogen and oxygen reaction. These findings demonstrate that the considered vdW HSs are promising candidates for spintronic and photocatalytic applications.