Dual-engine mode based on defective ZnCdS/hierarchical NiCo₂S₄ for full-spectrum photocatalytic hydrogen evolution

The development of efficient photocatalysts for solar-driven hydrogen production is crucial for addressing energy and environmental challenges. Herein, a full-spectrum responsive "dual-engine" photocatalytic system based on a multifunctional cocatalyst featuring electrons extraction, photothermal heating effect and abundant active sites was successfully designed. In this system, hierarchical NiCo₂S₄ (NCS)/defective ZnCdS (ZCS-Vs) composite photocatalysts were synthesized through a simple physical mixing method with hierarchical NCS modified ZCS-Vs nanoparticles. Owing to the introduction of black hierarchical NCS, these composite photocatalysts show a wide light absorption range from 300 to 1200 nm due to the introduction of black hierarchical NCS. Under broad-spectrum illumination, the optimized photocatalyst delivered a maximum H₂ production rate of 22.19 mmol·g^-1·h^-1 and an apparent quantum yield of 6.29 % at 420 nm, corresponding to roughly a 42-fold improvement over pure ZCS-Vs. This outstanding H₂ evolution performance originates from three key factors. First, the metallic nature and high work function of NCS enable the formation of a Schottky junction with ZCS-Vs, which efficiently extracts photogenerated electrons from ZCS-Vs for the reduction of H⁺ ions. Second, under photoexcitation, NCS exhibits a strong localized surface plasmon resonance (LSPR) effect, leading to a rapid increase in local temperature on the catalyst surface. This localized heating further elevates the overall reaction solution temperature, thereby reducing the energy barrier for photocatalytic H₂ evolution. Third, 3D hierarchical structure of NCS not only inhibits nanoparticle aggregation and provides abundant active sites, but also enhances light harvesting through internal scattering, thereby maximizing both charge separation and photothermal efficiency. Consequently, this "dual-engine" photocatalytic system provides a feasible pathway for designing photothermal-assisted composite photocatalysts to enhance photocatalytic H₂ evolution efficiency.