Preparation And Photocatalytic Performance Regulation Of CdS-based Composite Materials

With the rapid development of contemporary economy and society,environmental pollution and energy crisis are becoming more and more serious.It is found that the photocatalytic semiconductors which have unique advantages can be applied in many fields like environmental pollution,new energy development and so on.However,the confined photoresponse range for solar light of traditional semiconductors such as TiO₂ limits the development and application of photocatalytic materials.Therefore,designing novel,efficiency,environment-friendly and low-cost semiconductors have become hotspots in the photocatalytic field.Cadmium sulphide with more excellent photochemical properties in multitudinous semiconductors,has been widely investigated,the suitable band gap,high quantum efficiency and strong photocatalytic activity.Meanwhile,CdS also has the defects of easy recombination of photogenerated carriers and photocorrosion.In this paper,different semiconductors were selected to couple with CdS for modifying by constructing heterojunction,in order to enhance the photocatalytic activity and visible-light utilization.Moreover,the performance of photocatalytic degradation and hydrogen production was measured and discussed.The main contents of this study are as follows:?1?BiOBr nanosheets and CdS nanoparticles were prepared by hydrothermal method.The novel BiOBr/CdS composites was obtained by ultrasonic impregnation.The malachite green?MG?as the simulated pollutant was used to measure the performance and stability of photocatalytic degradation for composites.It was found that the highest degradability of MG achieved 99%within 100 min,and the mechanism of composites under visible-light irradiation was investigated by radical-trapping experiments.?2?CdS nanorods with the length of about 1 mm were prepared by solvothermal method,and the MnWO₄ nanoparticles grow on the surface of CdS by in-situ hydrothermal method to synthetize the MnWO₄/CdS composites.Under visible-light irradiation,the highest reductionrate of Cr???with composites was up to 98%,and still maintained with 90%at fifth cycle experiment.The synergistic effect between MnWO₄ and CdS suppresses the recombination of photogenerated carriers effectively and enhances the photocatalytic activity of composites,causing that MnWO₄/CdS composites exhibit the outstanding performance and stability of Cr???reduction under visible-light irradiation.?3?CdS and CdWO₄ composites were prepared by solvothermal method and hydrothermal method,and the CdWO₄/CdS composites was synthesized by ultrasonic immersion method.The malachite green as target pollutant was degraded by CdWO₄/CdS composites under visible-light irradiation.The highest degradation rate was up to 97%,and still maintained with 90%at fifth cycle experiment,demonstrating the excellent photocatalytic activity and stability.Meanwhile,average photocatalytic H₂ production rate of composites reached 2395.98?mol/h/g highest,which was much higher than that of CdS?657.67?mol/h/g?.The Z-scheme heterojunction between CdS and CdWO₄ remains the redox ability of composites,suppresses the recombination of photogenerated carriers effectively and enhances the photocatalytic activity of composites.?4?CoWO₄/CdS composites were prepared by solvothermal method and in-situ hydrothermal method,and the structure,morphology and photochemical properties of composites were measured.Under visible-light irradiation,the highest degradation rate of MG reached 97%,while the average photocatalytic H₂ production rate reached 15.91 mmol/h/g in 3h and maintained good photocatalytic stability.Because the migration of photogenerated carriers follows Z-scheme heterojunction,which enhances the photoabsorption ability for visible-light and recombination rate of photogenerated carriers.Moreover,the photoresponse range of composites is widened effectively on the basis of CdS.?5?Firstly,CdS nanorods were synthesized by solvothermal method,then ZnWO₄ nanoparticles were loaded on CdS nanorods by in-situ hydrothermal method to prepare ZnWO₄/CdS composites.The average photocatalytic H₂ production rate of the composites reached 79.27mmol/h/g highest in 3 h and maintained good photocatalytic stability which much better than that of CdS.The photogenerated carriers of CdS are separated due to the intimate contact between ZnWO₄ and CdS,which increases the lifetime of photogenerated electrons and obtains excellent property of photocatalytic H₂ production.