Sulfur-Deficient ZnIn₂S₄/Oxygen-Deficient WO₃ Hybrids with Carbon Layer Bridges as a Novel Photothermal/Photocatalytic Integrated System for Z-Scheme Overall Water Splitting

Although photocatalytic overall water splitting is a potential technology for converting solar energy into chemical fuel, the widely reported solar-to-hydrogen efficiency is around 1%, indicating unsatisfactory photocatalytic performance. Here, a novel photocatalyst material is designed and a whole reaction system is constructed, resulting in an integrative photothermal–photocatalytic Z-scheme overall water splitting reaction system. In terms of materials design, a novel sulfur-deficient ZnIn₂S₄/oxygen-deficient WO₃ (ZIS–WO) hybrid with surface-carbonized wood (C-wood) is reported. The ZIS–WO hybrid with sulfur and oxygen vacancies promotes the adsorption of visible light and the separation of charge carriers. The conductive C-wood is strategically used as an additional electron bridge to accelerate electron transfer. In terms of system construction, the C-wood exploits the photothermal effect to change the solid/liquid/gas triphase system to a solid/gas biphase system by transforming liquid water into steam, which drastically restrains carrier recombination, and decreases the photocatalytic reaction barrier. The H₂ and O₂ production rates in the proposed system are approximately 169.2 and 82.5 µmol h^–1 under air mass (AM) 1.5 light irradiation, and the corresponding solar-to-hydrogen efficiency is as high as 1.52%. The study from photocatalyst design to reaction system construct opens a new insight for versatile and high-performance photocatalytic overall water splitting.