Novel CdIn2S4 nano-octahedra/TiO2 hollow hybrid heterostructure: In-situ synthesis,synergistic effect and enhanced dual-functional photocatalytic activities

The development of highly efficient and multifunctional composite photocatalysts for both energy conversion and environmental governance has obtained great concerns. Here, a novel CdIn₂S₄/TiO₂ (CIS/THS) hollow composite photocatalyst was firstly designed and synthesized via a facile in-situ growth process, where the CdIn₂S₄ nano-octahedra densely attached on the surface of TiO₂ hollow spheres to form the unique hybrid heterostructure. The as-synthesized CIS/THS heterojunctions exhibit much superior photocatalytic activities for hydrogen evolution and Methyl Orange (MO) decomposition in comparison to pure CdIn₂S₄ and TiO₂ hollow spheres. The experimental results display that the CIS/THS-3 sample with the 30 wt% of TiO₂ presents the optimal photocatalytic H₂ production efficiency and its generation rate is 3.38 and 2.56 times as high as those of pure TiO₂ and CdIn₂S₄. Besides, the as-synthesized CIS/THS-3 hybrid also possesses the best MO photodegradation performance and its rate constant is 11.43 and 8.34 times higher than those of pure TiO₂ and CdIn₂S₄. The enhanced photocatalytic activities can be assigned to the synergistic effect, optimized light-harvesting capacity and the formation of hybrid heterostructure for boosting interfacial charge transfer and separation. Furthermore, based on the trapping experiments and ESR analysis, the possible type-Ⅱ interface charge transport mechanism was also proposed. Our study may provide the direct guidance for constructing other hollow TiO₂-based composite photocatalysts with superior photocatalytic water splitting and degradation performances.