Theoretical Investigation of Electronic and Photocatalytic Properties of a Trilayer vdW MoS₂/ZnO/WS₂ Heterojunction for Overall Water-Splitting Applications

Construction of a van der Waals (vdW) heterojunction is a promising approach with effective separation of charge carriers for intensified solar-to-hydrogen (STH) conversion efficiency. A trilayer MoS2/ZnO/WS2 heterojunction with two different configurations is constructed and their electronic and photocatalytic properties are investigated in detail. The heterojunction exhibited a type-II band alignment, where the ZnO monolayer is placed to the valence band maxima (VBM) position and MoS2 is contributed at the conduction band minima (CBM) of the heterojunction. In addition, trilayer heterojunction showed a high electron mobility of 454.12 cm2 V–1 s–1 and optical absorption intensity of 8.54 × 105 cm–1 in the visible region, which is much more significant than the individual monolayers. Interestingly, the MoS2/ZnO/WS2 heterojunction exhibited the maximum STH efficiency of 16.83%, which is much higher than the MoS2, ZnO, and WS2 monolayers and MoS2/ZnO and MoS2/WS2 heterostructures. S top acts as a brilliant adsorption site for hydrogen evolution reaction (HER). The theoretical overpotential value of the oxygen evolution reaction (OER) is 1.45 eV, much smaller than that of the MoS2 monolayer. The present study suggests that the construction of vdW vertical stacking of the trilayer heterojunction significantly enhances the photocatalytic activity with high carrier mobility, STH efficiency, and optical absorption in the visible region for overall water-splitting applications.