Preparation,Modification And Photocatalytic Properties Of CdS Micro-Nano Hierarchical Structured Materials

Photocatalytic technology is one of the effective ways to solve environmental pollution and energy crisis.In this dissertation,we have prepared a series of CdS micro-nano structured photocatalytic materials by green chemical synthesis.We investigated the nucleation mechanism of CdS nanocrystals.Meanwhile,The photocatalytic activity of the as-prepared products for the degradation of simulated dye wastewater bwas evaluated.The main research contents are summarized as follows:Firstly,Cu-based CdS thin films were prepared via a two-step method involving an electrodeposition process followed by solvothermal one.The as-prepared films were characterized by scanning electron microscopy?SEM?,X-ray powder diffraction?XRD?,energy dispersive spectrometer?EDS?and UV-vis diffuse reflectance spectroscopy?UV-vis-DRS?.The nucleation mechanism of CdS nanowires with the Cd microplatelets?MPs?as substrate and Cd source was also studied.The results show that the hierarchical CdS nanowired films with abundant channels were constructed with the Cd MPs electrodeposited on the Cu foil and the needle-like CdS nanowires grown on the Cd MPs.The size of CdS nanowires appears regular changes with the change of the concentration of thiosemicarbazide,solvothermal temperature and time.The Cu based CdS films show a high photocatalytic activity and good stability for the photocatalytic degradation of Rhodamine B?RhB?,and the degradation rate of RhB is 78.2%after recycling 5cycles.Secondly,using hydrothermal method to grow CdS nanosheets on g-C₃N₄ in situ to form CdS/g-C₃N₄ hierarchical structure.The results showed that CdS morphologies changed significantly.CdS changed from one-dimensional dendritic nanorods to two-dimensional nanorods.And these CdS nanoparticles are interspersed between layers of g-C₃N₄ to form a 3D hierarchical structure.This structure avoids the agglomeration of CdS.Compared with pure CdS,the specific surface area of CdS/g-C₃N₄ is 38.7 times larger.was used RhB dye solution as degradation model,and used CdS,g-C₃N₄ and CdS/g-C₃N₄ as photocatalysts.This were effected in visible light for 2h?500 W xenon lamp?.The results showed that the degradation rates of RhB were 56.3%,33.4%and 95.6%,respectively.CdS/g-C₃N₄ hierarchical structure significantly enhanced the visible light catalytic activity of CdS.The reasons were that CdS/g-C₃N₄ had a larger specific surface area and can provide more photoactive sites.CdS and g-C₃N₄ were constructed for a hierarchical structure,which can improve the separation and migration of photogenic carriers,and the catalytic activity was enhanced.The CdS/g-C₃N₄ showed no obviously loss of the photocatalytic activity and little change of structure after three cycles,which is vital in the application of photocatalyst.Thirdly,the CdS@g-C₃N₄ composite core-shell nanosphere structure were successfully prepared by hydrothermal with the action of ethylenediamine and EDTA-2Na.Also the nucleation mechanism of CdS@g-C₃N₄ was discussed.The specific surface area of CdS@g-C₃N₄composite core-shell nanospheres was 21.0 times that of pure CdS,with good photocatalytic activity and photostability.When the reaction conditions of 180?,4 h,CdS and g-C₃N₄ mass ratio was 1.9:1,the CdS@g-C₃N₄ visible light catalytic performance is best.The degradation rate of RhB was 95.2%,significantly higher than that of pure CdS.Repeated use 3 times,the structure and performance is basically the same.CdS@g-C₃N₄ core-shell structure can effectively avoid CdS agglomeration.At the same time,accelerate the migration velocity of hole to leave the CdS valence band,to avoid the light corrosion.In addition,the conjugate effect was also beneficial to the migration of photoelectron-hole pairs and improved the photocatalytic activity and stability.