In-Situ Formation of Spatially Oriented Interfacial Cu⁰ in Dual-Plasmon Resonance Coupling ZnIn₂S₄/Cu-Cu_3-xP Heterojunction for Full-Spectrum Photocatalytic Hydrogen Evolution

Integrating plasmonic materials can extend the light harvest and enhance photocatalytic H₂ production via localized surface plasmon resonance (LSPR). However, the sluggish utilization of LSPR-induced hot carriers due to poor interfacial coupling is the key issue. Here, we demonstrate a dual LSPR coupling ZnIn₂S₄/Cu-Cu_3-xP heterostructure with in-situ formation of spatially oriented interfacial Cu⁰, which is achieved by the interfacial electrons’ directional transfer from ZnIn₂S₄ to Cu_3-xP and partial reduction of Cu⁺ to metallic Cu⁰. The dual LSPR coupling of Cu and Cu_3-xP enhances absorption and localized electric field by 21.4-fold/7.1-fold in the visible region and 3.3-fold/1.4-fold in the near-infrared, respectively, achieving full-spectrum photon harvesting. More critically, the spatially oriented interfacial Cu⁰ acts as a charge transport channel, reducing the charge transfer activation energy by 65%, collectively prolonging the carrier lifetime by 707.7-fold, and boosting directional hot electrons extraction. Consequently, interfacial Cu⁰-induced dual LSPR effect achieves an order-of-magnitude enhancement in photocatalytic activity, reaching a value of 43.3 mmol g⁻¹ h⁻¹ that surpasses previous sulfide-based photocatalysts. This research highlights a reinforced interface charge transport pathway for directional hot carrier extraction via valence state modulation, paving a promising route for designing high-activity plasmonic photocatalytic systems.