Synergistic carbon vacancies and S-Scheme F-g-C3N4//FeIn2S4 heterojunctions for enhanced photocatalytic H2 evolution and organic dye degradation.

Engineering hierarchical heterostructures with clearly defined interfaces and effective routes of charge transport has become an important approach to solving problems related to environmental contamination and energy-related issues. Herein, we engineered a hierarchical (2D/3D) F-C3N4@FeIn2S4 (F-CN/FIS) S-type heterojunction via an in situ solvothermal approach to simultaneously tailor the interfacial charge behavior and electronic structure. Firstly, fluorine incorporation into F-g-C3N4 (F-CN) generates defect states and tunes the bandgap, thereby enhancing visible-light absorption and charge-carrier dynamics. Furthermore, coupling of F-CN with the narrow-bandgap FeIn2S4 (FIS) semiconductor via the S-scheme mechanism effectively suppresses charge recombination. It enhances photo-induced charge separation and promotes the production of reactive oxygen species (•O2-, •OH) while preserving strong redox properties. Consequently, the optimized F-CN/FIS-20% composite delivers an exceptional hydrogen production efficiency of 5881 μmol g-1 h-1 and exhibits superior photocatalytic degradation efficiency for organic pollutants when exposed to visible light, achieving 99.9% removal of Rhodamine B (RhB) (within 50 min) and 99% removal of Methylene Blue (MB) within 65 min. This synergistic effect of F-doped-CN-induced electronic modulation and the S-scheme heterojunction (F-CN/FIS), which promotes charge -carrier migration and accelerates interfacial reaction kinetics, boosts photocatalytic performance. This work offers a new strategy for the fabrication of advanced multifunctional heterostructured materials for photocatalytic applications.