Controllable Synthesis And Photocatalytic Performance Of Composite Catalysts Based On Ordered Mesoporous ZnS

The development of low-cost,easy-to-prepare,high-activity,and high-stability photocatalysts is a key technology in the semiconductor photocatalysis industry.Metal sulfides have long been the topic of research,especially in photocatalytic applications due to their special electronic structure.As an important n-type semiconductor material,ZnS is more friendly to prepare and easy to modify due to its tunable electronic structure and excellent optical properties.ZnS has a wide range of application prospects in solar energy conversion.Based on the above advantages,in this thesis,the ordered mesoporous ZnS is used as the host material because of its high specific surface area and multiple active sites,we have designed a composite photocatalyst with different compositions and structures by in-situ modification and loading method,to broaden the spectral range,promote the migration and separation of photogenerated carriers,and improve the photocatalytic activity.The specific work is summarized as follows:1.ZnSO4·7H2O as the precursor,KIT-6(orderly mesoporous silica)was selected as a hard template to synthesize the ordered mesoporous ZnS.The two-dimensional metal-organic framework(2D MOF,Cu-TCPP)was anchored on the ordered mesoporous ZnS framework by a low-temperature strategy(80℃).Strong electronic coupling is formed between the 2D MOF with multiple optical spectral responses and the ordered mesoporous ZnS,which successfully widens the optical spectral response range of ZnS.Under the light-illumination condition,the electrons are first excited in the 2D MOF of the composite and rapidly transferred to ZnS driven by thermodynamics.As an(active)carrier,ordered mesoporous ZnS can make full use of its electron-permeable framework and large specific surface area to provide abundant active sites for photocatalytic reactions,improve mass transfer efficiency,and improve the transport and separation of photogenerated carriers,showing highly efficient photocatalytic hydrogen production via water splitting.Compared with that of the pure ZnS,the time-resolved transient fluorescence test results show that the composite photocatalysts can effectively extend the lifetime of photogenerated electrons;under the standard sunlight,the composite catalyst ZMOF-0.07 presents the optimal photocatalytic H2 production efficiency and its generation rate is 5.9 times as high as those of pure ZnS.With continuous illumination for 30 h,the composite catalyst has good hydrogen-production activity and stability from photocatalytic water splitting.2.On the basis of ordered mesoporous ZnS,in situ synthesis of CdIn2S4/ZnS nanocomposite catalysts by a one-pot hydrothermal method.In the CdIn2S4/ZnS series,the band structure of octahedral CdIn2S4(EVB/Eg,-0.58/2.3 eV)matches well with those of ordered mesoporous ZnS(EVB/Eg,-0.54/3.4 eV),a Type Ⅱ heterojunction is successfully constructed,which beneficial to photogenerated electron-hole transport and separation.Under visible light irradiation,CdIn2S4 can be photo-excited to generate electron-hole pairs,and the photogenerated electrons can rapidly transferred to the ordered mesoporous ZnS under the strong thermodynamic driving force.The photocatalytic reduction reaction mainly occurs on the surface of the ordered mesoporous ZnS;the holes are rapidly trapped by hole-trapping agents in the octahedron CdIn2S4.Based on the advantages of ordered mesoporous ZnS,the CdIn2S4/ZnS nanocomposite catalyst is designed.The CdIn2S4/ZnS nanocomposite catalyst promotes the separation and migration of photogenerated charge carriers on the catalyst surface,improving mass transfer efficiency,thereby increasing the photocatalytic redox rate.Moreover,the composite photocatalyst CdIn2S4/ZnS not only presents a high hydrogen generation ability but also possesses the efficient activity for degrading rhodamine B.The effect of the composition of the composite photocatalyst CdIn2S4/ZnS on photocatalytic performance was systematically studied.The as-synthesized ZCIS-0.65 hybrid possesses the best RhB photodegradation performance and its rate constant is 89 times higher than pure CdIn2S4.In addition,the CdIn2S4/ZnS composite photocatalyst has good hydrogen-production activity and stability from photocatalytic water splitting after 20 h of i llumination.