Study On The Preparation And Properties Of CdS Composite Nanomaterials

CdS is an important II-VI semiconductors with relatively narrow bulk band gap (2.42 eV), which made CdS a competitive candidate as photocatalyst. Disadvantageously, the rapid recombination of the excited electron-hole pairs and limited available sun energy spectrum limit the applications in photocatalysis. It found that to design composite materials can greatly improve the photocatalytic performance.In this paper, we successfully prepared PbS hollow spheres, CdS/ZnS and CdS/graphene (CdS-G) composite materials:(1) Monodisperse PbS hollow spheres were successfully prepared via using CdS aggregate spheres as template. The present strategy achieved effective conversion from CdS to PbS by utilizing the solubility difference between the two materials. It was found that the reaction temperature played an important role in affecting the diffusion rate of the Pb²⁺ ions and the stability of formed primary crystals. Two growth mechanisms which are defined as kinetics-controlled process (KCP) and thermodynamics-controlled process (TDCP) were proposed for the two conversion patterns observed at 30°C and 90°C.(2) CdS/ZnS composite porous submicrometer spheres were synthesized through solothermal method to improve the photocatalytic activity of CdS. Using the narrowband semiconductor CdS to compound with ZnS was an effective solution, since it would enlarge the region of the absorption on account of the band overlap of the two, which would enable a more efficient utilization of nature light. Moreover, the interfaces at two materials exhibited distinctive physico-chemical properties in the semiconductors. These properties arised because of the difference in the crystallographic planes exposed at the interfaces, which in turn lead to in-homogeneity of atomic environments and to generation of certain microstructual defect centers at these sites. The certain microstructual defect at the CdS/ZnS interfaces provided a larger active surface area and the augmented number of reaction sites which may play a vital role in the better catalytic activity of the composite nanostructured semiconductors.(3) A facile solvothermal method was adopted to prepare CdS/graphene (CdS-G) composites. Graphene oxide could be well reduced by ethylene glycol under the solvothermal conditions. Meanwhile, the CdS particles were formed and scattered on the graphene surface. The photo-excited electrons transferred efficiently from CdS to graphene, and the charge separation is favorable for the application of as-prepared CdS-G composite as photocatalyst. The as-prepared CdS-G composites showed well activity and stability for visible light degradation of RhB.