In‐Situ Formation of Spatially Oriented Interfacial Cu ⁰ in Dual‐Plasmon Resonance Coupling ZnIn ₂ S ₄ /Cu‐Cu _3‐x P Heterojunction for Full‐Spectrum Photocatalytic Hydrogen Evolution

ABSTRACT Integrating plasmonic materials can extend the light harvest and enhance photocatalytic H 2 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 ZnIn 2 S 4 /Cu‐Cu 3‐x P heterostructure with in‐situ formation of spatially oriented interfacial Cu 0 , which is achieved by the interfacial electrons’ directional transfer from ZnIn 2 S 4 to Cu 3‐x P and partial reduction of Cu + to metallic Cu 0 . The dual LSPR coupling of Cu and Cu 3‐x P 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 Cu 0 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 Cu 0 ‐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.