Synthesis Of CeO₂ /CdS Nanophotocatalyst And The Application Research For Photocatalytic Degradation Of Rhodamine B

In this work,CdS nanorods（CdS） were prepared by solvothermal method, and then a heterostructures photocatalyst consisting of one-dimensional（1D） CdS nanorods（NRs） and cerium dioxide（CeO₂） nanoparticles（NPs） were successfully synthesized via a solvothermal method. Different characterization techniques were used to confirm the character of CdS/CeO₂. Field emission scanning electron microscopy（SEM） and transmission electron microscopy（TEM） were used to visualizing the detailed morphology and size of the synthesized products. The crystal structure and elements analysis of the as-prepared CdS NRs, CeO₂ NPs and CdS/CeO₂ nanocomposite were analysed by the X-ray diffraction（XRD） and the patterns X-ray Photoelectron Spectroscopy spectra（XPS）. The light adsorption properties were detected by UV-visible diffuse-reflectance spectra（UV-vis DRS） and the Brunauer-Emmett-Teller（BET） specific surface area and pore size were measured with an automatic instrument.Besides, the visible-light-driven photocatalytic activit y was evaluated by the discoloration of Rhodamine B（Rh B）. The temporal evolution of the spectral changes and the mechanism during the photodegradation of RhB over CdS/Ce O 2 and CdS were also observed by HPLC instrument system, the total organic carbon（TOC） assays and UV-Vis spectrometry etc, respectively. To probe the practical reusabilit y of the CdS/CeO₂ catalyst in the decomposit ion of Rh B, recycling tests were carried out by repeated reaction cycles under the same reaction condit ion. To further demonstrate the stabilit y of the catalyst, leaching of cadmium from CdS/CeO₂ in solution after six cycle test was measured by via a Perkin-Elmer Analyst 700 atomic absorption spectrophotometer. In addit ion, some factors which may affecting the catalytic degradation of the dye such as the CeO₂ content of compounds, p H value,inorganic salt mental ions and init ial Rh B concentration in the reaction.SEM and TEM images showed that the highly ordered CdS NRs displayed an average rod diameter of about 100 nm wit h a length of 1² μm, and the CeO₂ were were intimately attached on the wall of the CdS NRs. XRD patterns of the as-prepared CdS/CeO₂ nanocomposite showed that samples was composited of cubic structure of CeO₂ and hexagonal structure of CdS. XPS results indicated that there were higher surface adsorbed oxygen amount on CdS /CeO₂, which was related to the CeO₂ and helpful for the photocatalytic pollutant degradation. The nitrogen adsorption-desorption isotherms indicated that the total pore volume of CdS/CeO₂ is increased a lot, which may come from the voids between the aggregated CeO₂ particles and CdS rods.It was also indicated that, under visible light illumination, the photocatalytic rate constant of CdS/CeO₂（Rc=20）exhibit a best degrading abilit y（ nearly 3.4 times and 28 times higher than that of pure CdS and pure CeO₂, respectively）, and the degradation experiment can be described by pseudo-second order model and Langmuir isotherm equations.HPLC results showed that the Rh B was effectively decomposed rather than merely bleached during the CdS/Ce O 2-assisted photodegradation. A relatively high mineralization rate of TOC removal was achieved, indicating that Rh B has been mineralized efficiently under visible light irradiation. CdS/CeO₂ displayed a strong structural stabilit y during the photocatalytic oxidation of the pollutant molecules. It was notable that the superoxide anion radical was the major oxidative species responsible for the photooxidative conversion of Rh B. In addit ion, degradation mechanism of Rh B on CdS/Ce O 2 was also discussed. Meanwhile, the Rh B degradation efficiency increased wit h the decay of p H and declined as the init ial Rh B concentration increase d. The deceleration effect of metal ions on the destruction rate displayed the following order: Cu2+ > Ag+ > Zn2+ > Fe3+. In addit ion,CdS/CeO₂ could not only make the conjugated stmctures decomposed but also as well as the aromatic parts of the dye gradually mineralized to H2 O and CO2,etc.during its degradation.Overall, the combination of CdS NRs and CeO₂ NPs improved the degrading abilit y of catalyst and inhibited the recombination of electrons and hole as well as photocorrosion of CdS.