Study On Preparation And Properties Of Functional LDHs Composite Materials

In recent years,the study of functional composite materials has been a hot spot in the field of chemistry.The layered double hydroxides(LDHs),a kind of supramolecular material with unique characteristics of layered structure,due to its laminate metal type and layer spacing controllable features,have a very good application prospect in the adsorption,catalytic,energy storage,etc.In view of the special 2D structure and variable adjustability of LDHs,we in the paper are mainly concentrated on the preparation of LDHs with different metal,and have designed several kinds of LDHs to build the target functional composites.Also,we focus on the application of this type of composite materials in many aspects,such as in the field of gas absorption and supercapacitor and so on,where show excellent properties and good prospects.In the first chapter,we summarize systematically about LDH materials,including the basic concept,the architecture of LDHs,different synthesis methods and the applications mentioned in the literature,and so on.Furthermore,some of the latest research results at home and abroad are introduced in detail.In the second chapter,a variety of LDHs prepared in the experiment are overall summarized,such as ZnAl LDH,CoAl LDH,which lay the foundation for the next stage of the design and preparation of the LDHs based composite materials.In the third chapter,we synthesis the ZnAl LDH@ZIF-8 composite materials,taking good advantage of the structural characteristics of MOFs,such as porosity,high specific surface area and high stability.This is the first time to our knowledge that in the absence of any Zn source,a layer of dodecahedral ZIF-8 nanocrystals on the regular hexagonal ZnAl LDH nano films is synthesized by in situ growth.Through the systematic analysis,we can find that this kind of ZnAl LDH@ZIF-8 composite material with regular morphology is successfully constructed.The adsorption test of CO2 based on this ZnAl LDH@ZIF-8 composite material in low pressure and at room temperature shows ideal results.The CO2 adsorption amount of the ZnAl LDH@ZIF-8 composite is 1mmol·g-1 under the condition of 1 bar and room temperature.By comparison,it is significantly higher than either of the single materials,which can be speculated that after successful construction the performance of this composite material can be improved due to the synergistic effect between the two monomer materials.In view of the ideal CO2 adsorption property of ZnAl LDH@ZIF-8 composite synthesized at low temperature,the adsorption of CO2 under high temperature and high pressure can try to be avoided,which can not only avoid danger but also save resources with good application prospect.In the fourth chapter,we design and synthesis NiO/NiMn(Fe)LDH nano-layered composite materials,and focus on the performance of the supercapacitor based on this material,taking good use of the high charge transfer rate and high stability of transition metal oxides(TMO).This material was prepared by two steps.Firstly,the NiO thin film was prepared on the surface of nickel foam,and then a LDHs film was grown on the surface of NiO film.Through the systematic analysis,it can be seen that this kind of composite membrane with regular morphology is successfully constructed.In the supercapacitor test,the electrochemical performance of the prepared NiO/NiMn(Fe)LDH is not only much higher than that of any single materials,but also is higher than the previously reported composite materials based on NiO.In addition,the asymmetric supercapacitor was prepared by using activated carbon as negative electrode and NiO/NiMn LDH composite film as positive electrode.The test results show that the composite has good performance.In summary,we in this paper are dedicated to the design and synthesis of LDHs based functional composite materials,and systematic analysis is implemented based on a series of materials.Especially,we have deeply investigated the performance of this kind of materials in gas adsorption,catalysis and supercapacitor,etc.which is conducive to promote the development of this kind of composite materials and expand the application range.