A dual Z-scheme ZnS@g-C3N4@ZnIn2S4 heterojunction for enhanced photocatalytic selective oxidation of toluene

Abstract

Rational design of advanced heterojunction architectures represents a promising approach for optimizing the semiconductor photocatalyst performance in selective toluene oxidation. This study demonstrates the successful synthesis of a dual Z-scheme ZnS@g-C₃N₄@ZnIn₂S₄ heterojunction composite through hydrothermal processing, featuring co-loaded ZnS nanoparticles and fragmented g-C₃N₄ (FCN) on ZnIn₂S₄ surfaces. The optimized photocatalyst achieved an exceptional toluene conversion rate (21.6 mmol g⁻¹ h⁻¹) with 78% benzaldehyde selectivity under O₂ oxidation conditions. Comprehensive characterization revealed that the unique dual Z-scheme configuration enhances the charge separation efficiency through expanded interfacial contact and increased active sites. Combined experimental and computational analyses verified favorable redox potentials and efficient photogenerated carrier separation, with mechanistic studies identifying hydroxyl (˙OH) and superoxide (˙O₂⁻) radicals as key reactive species enabling multipath conversion pathways. This work establishes fundamental principles for developing high-performance catalytic materials while advancing practical strategies for selective aromatic hydrocarbon conversion under mild reaction conditions.