Defective ZnIn₂S₄/NiO Z-scheme heterostructure for photothermal-assisted high performance photocatalytic hydrogen evolution under visible light

The photocatalytic hydrogen evolution reaction (HER) has received significant attention for its potential to efficiently harness renewable solar energy, producing green hydrogen fuel and oxygen as a by-product, thereby addressing the global energy crisis. However, bare photocatalysts such as ZnIn₂S₄ often exhibit limited performance in water splitting due to their narrow light absorption spectrum, inadequate photoinduced charge carrier mobility, significant charge recombination, and sluggish surface kinetics. This study developed a novel two-dimensional (2D) ZnIn₂S₄/nickel vacancies-rich NiO (V_Ni–NiO) heterostructured nanosheet (ZnIn₂S₄/V_Ni–NiO) using a facile low-temperature reflow strategy. The resulting 2D ZnIn₂S₄/V_Ni–NiO heterostructure demonstrated a high visible-light photocatalytic HER rate of 9.8 mmol g⁻¹ h⁻¹ and an apparent quantum efficiency of 5.68 % (λ = 420 nm), representing approximately a sevenfold improvement compared with pristine ZnIn₂S₄ photocatalysts. The exceptional photothermal properties of V_Ni–NiO continuously generate internal heat under visible light irradiation, increasing the local temperature of the photocatalyst and accelerating charge migration. Several synergistic mechanisms contribute to the enhanced performance. Firstly, the introduction of V_Ni–NiO species effectively broadens the light response region to the visible light spectrum. Secondly, the Z-scheme heterojunction, with optimal band alignment at the ZnIn₂S₄/V_Ni–NiO interface, creates an internal electric field that promotes carrier separation. Furthermore, the unique 2D nanosheets enriched with nickel vacancies provide numerous active sites, while the porous channels within the photocatalyst facilitate efficient physical transport and allow the generated gases to escape. This study presents a critical advancement in photocatalytic HER, that underscore the potential for scalable and efficient green hydrogen production, a viable solution to the global energy crisis. © 2025 The Authors