Dual-Valence Cu0/Cu+ Interfacial Sites in ZIF-Derived C–N/ZnIn2S4 Heterostructure: Interface-Mediated Charge Separation for Photocatalytic Hydrogen Evolution

Abstract Confronted with the dual challenges of freshwater scarcity and the global energy crisis, seawater splitting for hydrogen evolution has emerged as a promising research frontier in hydrogen energy, as it directly utilizes abundant seawater resources and enables clean energy conversion driven by solar irradiation. This study aims to develop a high-efficiency photothermal-coupled photocatalyst for seawater hydrogen evolution and to elucidate the synergistic enhancement mechanism of the photothermal synergy. Herein, we rationally design a core–shell photocatalyst consisting of a Cu0/Cu+-embedded carbon–nitrogen (CN) core encapsulated by sulfur–indium–zinc nanosheets, and successfully achieve high-efficiency photocatalytic hydrogen production. Under simulated sunlight irradiation, the catalyst exhibits excellent hydrogen production activity. Its hydrogen production rate reaches 3045.98 μmol g–1 h–1 in aqueous solution with 10 vol % triethanolamine (TEOA) and remains as high as 2132.36 μmol g–1 h–1 in simulated seawater (10 vol % TEOA). The superior photothermal-coupled performance arises from its unique core–shell structure. The localized surface plasmon resonance (LSPR) effect of metallic Cu nanoparticles in the core (CCN) improves photothermal conversion and raises system temperature. Such temperature elevation not only accelerates surface reaction kinetics and reduces the apparent activation energy of photocatalytic H2 evolution, but also promotes photogenerated charge separation and migration, mitigating energy loss from carrier recombination. Meanwhile, Cu0-Cu+ heterointerfaces in the core speed up electron transfer, avoid electron accumulation on Cu, and further suppress carrier recombination. Besides, the cracked and porous CCN-modified CN matrix enhances water transport, facilitates water diffusion and contact with active sites, and elevates hydrogen evolution efficiency. This work verifies that the synergy of the LSPR effect and porous water transport channels is critical for solar-to-hydrogen conversion, and provides an innovative strategy to construct high-performance photothermal synergistic photocatalysts.