Porous, Two-dimentional Inorganic Composite Materials And Their Application On Catalysis And Electrochemistry

Inorganic composite material is one kind of the most important functionalmaterials. It is composited of different component materials with hierarchicalmicro-/nanostructures. According to the complementation of the properties ofcomponents and their related synergistic effect, the compounds are with excellentproperties. Based on the unique feature of structure, the porous and two-dimentionalinorganic compounds have widely applications in petroleum refining, automobile andaviation, etc. However, as the problems of environmental pollution and the energyshortage get more serious, it is highly desirable to develop novel porous,two-dimentional inorganic material with high performances. For example, in the fieldof catalysis, the design of novel automobile exhaust gas purification catalyst is highlyneeded to effectively cut the loading amount of noble metals in the catalyst withoutsacrifice of performance; In the field of electrochemical lithium storage, thedevelopment of novel lithium-ion battery material with high capacities, good cyclingperformance and excellent rate capability is extremely needed to meet the requirementof electro mobile. Hence, the development of novel porous, two-dimentionalinorganic composite material and the investigation of composite structures,synergistic effect and their effects on performances in special applications are of greattheoretical and practical significance. In this thesis, we attempted to synthesize novelporous, two-dimentional inorganic composite material with unique structure andexcellent performance, and discuss the key issues in their synthetic process. Thelithium storage and catalysis properties of the obtained structures as well as therelations between their structures and performances have been studied. Detailed research contents are summarized as following:(1) Controlled synthesis of noble metal-microporous zeolite compound and theirapplications in catalysisThe compounds of platinum and SAPO-44microporous zeolite were synthesizedthrough a improved impregnation approach. The techniques of X-ray adsorptionspectra, transmission electron microscopy and temperature-programmed reductionwere used to investigate a dispersed state and size of platinum supported on externalframework of SAPO-44zeolite. The results show that the platinum is mainlydispersed as metal nanoparticles with size of2-4nm, which could be stable in air.Furthermore, we investigated their performance in the catalytic purification ofautomobile exhaust gases (CO, NOxand hydrocarbons). The results demonstrate thatthe Br nsted acid sites on the external surface of a microporoussilicoaluminophosphate (SAPO) act as a promoter for exhaust gas purification,effectively cutting the loading amount of platinum in the catalyst without sacrifice ofperformance.(2) Controlled synthesis of multilayered graphene/MoS2heterostructures andtheir applications in lithium-ion batteries with superior rate performanceMultilayered graphene/MoS2heterostructures were successfully synthesizedthrough a simple heating procedure by using sodium sulfate crystals as twodimensional structure template and a source of sulfur, Mo-oleate as sources of carbonand Mo. The results of structural characterizations show the two dimensionalheterostructure is assembled by atomic crystals of MoS2and graphene with flatsurface, uniform structures and large surface area of>160μm. Furthermore, thenumber of MoS2sheets in the graphene/MoS2heterostructured films can be controlledby varying the molar ratio of MoCl5to sodium oleate. Moreover, when used as ananode material for lithium batteries, the heterostructured films show excellentperformance. Especially for sample GM2, taking advantage of the greatly shortenedlithium ion diffusion distance and the outstanding electronic conductivity, it exhibitshigh specific capacity, excellent rate performance and cycling stability even at highcurrent densities.(3) Synthesis of tin oxide nanocrystals/carbon film hybrids and theirapplications in lithium-ion batteries with superior rate performanceTin oxide nanocrystals/carbon film hybrids were successfully synthesized through asimple heating procedure by using the surface of sodium sulfate crystals as twodimensional structure template, tin-oleate and SnCl4as sources of carbon and tin. The results show that tin oxides nanocrystals are uniformly dispersed in the graphitizedcarbon framework with homogenous size distribution and mean size of2-3nm.Furthermore, the obtained material shows excellent performance in the application oflithium-ion battery. Large discharge capacities of approximately826,728, and400mAh g-1are retained at0.5,1.0and10.0A g-1, respectively after50cycles. The highperformance is attributed to its unique compound structure, which can provideextremely large electrodes’ surface area for high capacity density and ultrafastcharge/discharge rate, and be capable of high resistance to the capability degradationcaused by strong volume expansion of anode during cycling. Moreover, the behaviorof graphitized carbon film coating can avoid direct contact between electrolyte and tinoxide nanocrystals to reduce the adverse reactions at their interface and greatly improve thecycling stability of the material.