Study On Preparation And Application Of Composites Based On Ultra-Thin Two-Dimensional Nanomaterials

This doctoral thesis attempts to introduce the latest research progress related to ultra-thin two-dimensional nanomaterials,focusing on the acquisition,characterization,assembly and catalytic and lithium-ion-battery's applications of graphene oxide(GO),ITQ-2 ultra-thin molecular sieves and ultra-thin TiO2 obtained by liquid phase stripping.For the liquid phase exfoliation of layered materials,based on the introduction of the stripping mode and mechanism,this paper focuses on the key technologies to control the morphology,phase,doping,defects,size,number of layers and crystal orientation.The defects of ultra-thin 2D nanomaterials represented by GO are also discussed.Then the composition,structure and testing methods of ultra-thin 2D nanomaterials are introduced,as well as the various raw materials,structure and properties and the equipment needed for synthesis.Finally,the composite structures based on ultra-thin two-dimensional materials are introduced in chapters,including vertical composites and coated composites,as well as the application of composite structures.The details are as follows:(1)GO coated MnO2 nanowires.Taking advantage of the large surface area and electrical conductivity of GO,the redox activity of the composite structure was maintained,and the MnO2 was fully coated and protected with a very small amount of GO.A small amount of amorphous TiO2 formed by hydrolysis of TiCl4 at low temperature was selectively deposited on the oxygen-containing functional groups of GO tube by atomic layer deposition technique to adjust the oxidizability of the catalyst.Compared with pure MnO2,GO/MnO2 composite catalyst has delayed oxidation and stronger resistance to SO2 poisoning.(2)A series of GO and vanadate composite nanoribbons were hydrothermally synthesized with GO as the structure guiding agent,which expanded the composition of the nanoribbons.GO is located in the interior of the composite structure,which supports the main structure and does not affect the surface mass transfer process.Compared with other GO-based composite structures(such as GO tube and GO sheet),the GO band-based composite structure has better application effect in lithium-ion battery.(3)positively charged Co(OH)2 nanosheets and negatively charged ultra-thin TiO2 nanosheets were synthesized and assembled together by electrostatic assembly,and then calcined with LiOH for a short time.Through this method,Ti in ultra-thin TiO2 is successfully doped into LiCoO2.The advantage is that when the phase transition occurs in Ti-doped LiCoO2,the Li+diffusion coefficient remains unchanged.The structure will not be seriously compressed or stretched.After 200 cycles,the reversible capacity is increased from 22%without doping to 97%.(4)Two ultra-thin 2D nanomaterials,GO and ITQ-2 molecular sieves,were simultaneously acted on MnO2 nanowires to form composite NH3-SCR catalysts with gradient acid sites.When the reaction temperature is higher than 200?,even a small amount of SO3 can be immobilized on ITQ-2 molecular sieve instead of covering the active center of the catalyst,which broadens the temperature range of SO2 resistance of Mn-based NH3-SCR catalyst to a certain extent.I believe that the introduction of GO,ITQ-2 and TiO2 in this paper will provide some reference for researchers in different fields.