First-principle investigation of electronic coupling and charge transfer in ZnO/VS₂ Z-scheme heterostructure for superior photocatalytic water splitting

Hydrogen energy is pivotal in facilitating a green and low-carbon transition, and solar irradiation offers a viable pathway for producing clean hydrogen. However, its efficiency is hindered by rapid electron-hole recombination. In the present study, this limitation is addressed by constructing a ZnO/VS₂ heterostructure that generates an interfacial electric field to improve charge separation and prolong carrier lifetimes. First-principles calculations reveal that the ZnO/VS₂ van der Waals heterostructure combines thermodynamic stability, confirmed by binding energy, elastic modulus, and AIMD simulations, with strong photocatalytic potential for the hydrogen evolution reaction (HER) under visible light. Differential charge density mapping shows an intrinsic interfacial electric field that improves charge separation, enabling spontaneous redox-driven water splitting at pH = 0. The heterostructure achieves a peak solar-to-hydrogen efficiency of 38.3 % and carrier mobility of 2882.14 cm²/Vs. Biaxial strain (−3 % to +3 %) progressively narrows the band gap, while hydrogen adsorption analysis yields a near-optimal ΔG_H confirming favorable HER thermodynamics. These results position ZnO/VS₂ as a potential photocatalyst for high performance solar hydrogen production.