Enhanced visible light photocatalytic activity of CdS through controllable self-assembly compositing with ZIF-67

Enhanced light absorption, improved separation of photoelectrons and holes, and controllable electron transfer paths are important ways to improve photocatalyst performance. In this work, a convenient but more efficient method is adopted to prepare composite photocatalysts integrating narrow gap semiconductors and zeolitic imidazolate frameworks (ZIFs). We chose ZIF-67, a typical ZIF, as the model and integrate it with CdS to self-assemble into highly crystalline ZIF-67@CdS composites. Extensive characterization methods (e.g., XRD, FE-SEM, UV-vis DRS, Raman, XPS, HRTEM, TEM, M-S, EIS and FT-IR) were applied to understand the correlations between performance and interface structure and morphology of the composite catalysts. Results demonstrate that the performances of the composite catalysts were greatly improved. ZIF2@CdS100 with optimized particle size (200 nm), limited shell thickness (less than 100 nm) and the shape of sugar gourd strings with Z-scheme interface structures was the best. Its H-2 evolution rate and degradation rate constant of methylene blue (MB) under visible light irradiation were up to 6.7 and 3.1 times over those of bare CdS nanorods, respectively. Possible mechanisms of structure-morphology-performance were proposed. Optimizing the size and shape of composites can be used to regulate the morphology and interface structures of the composite catalysts to enhance their visible light photocatalytic activities.