High-efficiency photocatalytic water splitting via direct Z-scheme charge transfer in GaN/ZrS2 van der Waals heterojunction

Abstract

Employing density functional theory-based first-principles computations, the optoelectronic properties and photocatalytic water splitting performance of the GaN/ZrS₂ van der Waals heterostructure are comprehensively investigated, along with the regulatory effect of biaxial strain. The GaN/ZrS₂ heterojunction forms a type-II band alignment with efficient charge separation enabled by van der Waals interactions and Z-scheme charge transfer. The GaN/ZrS₂ heterojunction achieves a visible optical absorption rate of up to 13 %, with the absorption spectrum exhibiting a pronounced red shift, significantly superior to single-component materials. Catalytic performance calculations show that the GaN/ZrS₂ heterojunction, driven by the synergistic effect of the interfacial built-in electric field and the Z-scheme charge transfer mechanism, enables the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to proceed spontaneously, with a solar-to‑hydrogen efficiency (${\eta }_{\mathrm{STH}}$) of 28.02 %. Biaxial strain regulation of the GaN/ZrS₂ heterojunction reveals that compressive strain (−6 % to 0) decreases the bandgap while inducing a red shift in the absorption edge, whereas tensile strain (0 to 10 %) leads to bandgap widening and a blue shift of the absorption edge, demonstrating the effectiveness of strain engineering in tuning optical absorption. The study demonstrates the broad application prospects of the GaN/ZrS₂ heterojunction in photocatalytic water splitting.