Fabrication of a 3D/0D S-scheme heterojunction based on ZnO nanoflowers and ZnIn2S4 nanoparticles with enhanced CO2 photoreduction performance

Abstract

To address the challenges of easy agglomeration, inadequate adsorption capacity, and low electron separation efficiency of pure ZnIn₂S₄ during the CO₂ photoreduction process, a novel 3D/0D ZnO/ZnIn₂S₄ S-scheme heterojunction was fabricated by growing ZnIn₂S₄ nanoparticles (NPs) in situ on the surfaces of ZnO nanoflowers (NFs). By regulating the loading amount of ZnIn₂S₄ NPs, ZnO/ZnIn₂S₄ composites with high catalytic activity were obtained. The optimal performance was observed for the sample ZZ8 (ZnIn₂S₄ : ZnO = 8 : 100 molar ratio), achieving the maximum CO₂ photoreduction rates. Under 4 h UV-vis light irradiation, ZZ8 produced CO and CH₄ of 149.38 μmol g⁻¹ and 94.39 μmol g⁻¹, respectively, corresponding to 3.44 times and 5.51 times the rates of pure ZnIn₂S₄. The optimal ZnIn₂S₄ loading significantly expanded ZZ8's effective adsorption area and pore structure, enhancing CO₂ adsorption, activation and reactant diffusion. Concurrently, Zn–In bimetallic sites markedly boosted CO₂ adsorption and activation capacity, inducing a synergistic catalytic effect. After 10 reaction cycles, the CO production rate remained above 85%, indicating excellent photostability of ZZ8. Comprehensive analysis confirmed an S-scheme electron transfer pathway in the ZnO/ZnIn₂S₄ composite during CO₂ photoreduction, enabling efficient spatial separation of photogenerated charges. This study effectively optimized the photocatalytic performance of the material through morphology control and the construction of an S-scheme heterojunction. It provides a theoretical basis and a technical pathway for the rational design of other 3D/0D S-scheme heterojunction photocatalytic materials (e.g., ZnO/g-C₃N₄, ZnO/MoS₂).