Study On Preparation Of Cadmium Sulfide-based Photocatalytic Material And Its Photocatalytic Performance Under Visible Light

In recent years,semiconductor photocatalysis technology has been extensively studied to solve the problem of global energy shortage and environmental pollution.Cadmium sulfide（CdS）is a promising photocatalyst owing to its specific band structure and strong absorption in the visible light range.CdS has attracted considerable attention due to an adequate narrow band gap（2.4 eV）and proper thermodynamic conduction band potential.However,due to its inherent defects,including the severe photocorrosion and rapid recombination of photogenerated electron-hole pairs,the development and application of cadmium sulfide（CdS）semiconductor materials are severely restricted.To address those issue,herein,we develop some beneficial explorations on CdS from morphology tuning,facet control and cocatalysts loading.The main research results are as follows:（1）Based on morphology tuning,different sulfur sources were selected,and cubic phase CdS semiconductor materials with different morphologies were prepared by one-step mixed solvothermal method.The effects of varying sulfur sources on the surface morphology and energy band structure of CdS semiconductor materials were studied by SEM,XRD,UV-vis DRS and etc.Photocatalytic hydrogen evolution and degradation experiments show that nano-particle cubic phase CdS has the best photocatalytic activity.Under visible light irradiation,its hydrogen production rate is as high as943.54μmol g^-1h^-1and AQE is 10.58%,which is comparable to some Pt@catalyst systems.In addition,the experimental results of photocatalytic degradation of RhB show that the degradation rate of RhB by CdS nanoparticles is greater than 99%within 30 minutes.The enhanced photocatalytic activity is attributed to the synergy of the high reduction potential,high charge separation rate and appropriate band structure of CdS nanoparticles.（2）Based on facet control,hexagonal CdS with different ratios of（002）and（101）crystal facets exposure areas were prepared by adjusting the reactant feed ratio,reaction temperature and holding time.The photocatalytic activity of CdS is intently related to（002）and（101）crystal facets.The photocatalytic hydrogen evolution experiment illustrates that the photocatalytic activity has a volcanic relationship with the exposure of（002）and（101）crystal facets,indicating that appropriate exposed（002）and（101）crystal facets can significantly enhance the photocatalytic activity of CdS.The enhanced photocatalytic activity is attributed to the synergy between the（002）and（101）crystal facets,which greatly promotes the transfer rate of charge carriers and suppresses the recombination rate of photogenerated electron-hole pairs in CdS semiconductor materials.（3）Based on the cocatalyst modification,the acid-oxidized carbon nanotubes（O-CNTs）and CdS spherical nanoparticles（SNPs）were combined by hydrothermal method.The results showed that the photocatalytic degradation activity of CdS SNPs was significantly enhanced with O-CNTs modification.Under visible light irradiation,the degradation rate of Rhodamine B（RhB）and methyl orange（MO）by O-CNTs/CdS SNPs reach 98%and 95%,besides,the O-CNTs/CdS SNPs composites show a better performance and stability.Therefore,the enhancement mechanism of O-CNTs cocatalyst on CdS photocatalytic activity is proposed:Under visible light irradiation,electrons（e^-）are excited from VB of CdS SNPs to CB,leaving holes（h⁺）in VB.Due to the superior electrical conductivity of O-CNTs,O-CNTs electronic additives can not only quickly transfer photogenerated electrons on the surface of CdS,but also act as degradation active sites,promote interface reduction reactions,and significantly enhance the photocatalytic activity of CdS SNPs.