Research On The Preparation And Photocatalytic Performance Of CdS Based Nanocomposite Materials

CdS with the band gap of 2.4 eV,is the most important II-VI semiconductor,has been widely studied.Because of its proper band gap and the appropriate band position makes it the most application value of the photocatalytic materials,which is widely applied in the photodegradation of organic pollutants and the photoproduction of hydrogen.However,it still exist some defects.Such as the effective recombination of electronic-hole and the CdS particles are easy to reunite in the catalytic reaction,which will reduce its surface area and the available active species,then reduces its photocatalytic activity.To increase the efficiency of CdS and suppress the phenomenon of photocorrosion,to combine it with the carbon nanotubes or another kind of semiconductor is a kind of effective way to solve this problem.In this thesis,multi-walled carbon nanotube?MWCNT?or combine it with another kind of semiconductor to prepare some photocatalysts.The properties and shape of the samples were measured by XRD,FESEM,TEM,Raman,FTIR,PL and UV-vis methods.Under visible light irradiation the photocatalyst were assessed to degrade different pollutants and investigate the stability of the photocatalyst.The main research work containing some aspects as following:?1?Multi-walled carbon nanotube?MWCNT?as raw material,through solvothermal method to prepare the CdS QDs/MWCNT composite photocatalyst.The CdS QDs nanoparticles with the size of 5-8 nm were uniformly well-dispersed on the surface of the MWCNT.Under visible light irradiation,the CdS QDs/MWCNT composite photocatalyst for the degradation of malachite green?MG?was much better than the purified MWCNT.The enhanced photocatalytic activity was mainly attributed to the highest separation efficiency of photo-induced electrons and holes.?2?The CdS/BiVO₄ nanocomposites were fabricated by solvothermal method.The CdS nanoparticles were uniformly well-dispersed on the surface of the BiVO₄.All CdS/BiVO₄ photocatalysts exhibited significantly enhanced photocatalytic activity,and the 1.5-CdS/BiVO₄ showed the highest photocatalytic activity.The CdS/BiVO₄ photocatalysts exhibited higher photocatalytic activity under visible light irradiation for the photodegradation of malachite green?MG?.The mechanism was confirmed that the synergetic effects of the CdS and BiVO₄ lead to efficient charge separation and inhibited the recombination of electron and holes.?3?The CdS nanorod was prepared by controlling the temperature,the ZnFe₂O₄/CdS composite photocatalyst was prepared by ultrasonic immersion method.The ZnFe₂O₄ nanoparticles with the size of 5-10 nm were uniformly well-dispersed on the surface of the CdS nanorod,with sizes varying from 10 to 30 nm.The ZnFe₂O₄/CdS photocatalysts exhibited significantly enhanced photocatalytic activity than purified ZnFe₂O₄ and CdS under visible-light irradiation for the Cr?VI?reduction reaction.The photocatalytic mechanism shows that ZnFe₂O₄/CdS composite has stronger optical absorption,the contact force between ZnFe₂O₄ and CdS,and the matched potential to improve the photocatalytic activity,the photocatalytic reduction rate could reach to 80% after 5 cycle times?4?The BiOCl@CdS/Ag₂CO₃ nanocomposites were prepared via in situ precipitation method.The BiOCl@CdS/Ag₂CO₃ heterojunction composite photocatalyst has better ability of visible light response.The photocatalytic experiment showed that the 5wt%-BiOCl@CdS/Ag₂CO₃ had the highest photocatalytic activity.Under visible light irradiation,the nanocomposite photocatalyst for the degradation of rhodamine?RhB?is obviously higher than that of Ag₂CO₃/BiOCl,which is mainly attributed to the incorporation of CdS can effectively inhibit the recombination of electrons and holes.