Synthesis And Properties Of Hierarchical SnS₂（SnO₂） Micro-/Nanostructures

SnS₂and SnO₂are important tin based componds with excellent optical, catalytic,magnetic and gas sensitive properties and have wide applications in gas sensor,resistor, photodevice, photoconductor, luminescent materials, photocatalyst, lithiumion batteries, etc. Recently, inorganic fuctional materials with hierarchicalmicro-/nanostructures have attracted intensive interest for the structure joined theintrinsic effect of bulk materials with the nano-effect of nanomaterials and producedmany combinatory effects. Hierarchical micro-/nanostructures have been showattractive superiority in energy conversion, such as solar cells and photocatalytichydrogen generation, energy storage, such as lithium ion batteries and supercapacitor,sensor, catalysis, water treatment and so on. A solution-phase chemical method wasone of the most promising routes in these reports, due to its low cost and potentialadvantage for large-scale production. Exploration of reasonable synthetic methods forcontrolled construction of hierarchical micro-/nanostructures of tin basedchalcogenide via a chemical self-assembly route is still an intensive and hot researchtopic. In this thesis, we attempted to synthesize hierarchical SnS₂（SnO₂）micro-/nanostructures by new chemical method. The lithium strage, optical and gassensitivity properties of the obtained structures as well as the ralations between theirstructures and performances have been studied. Detailed rerearch contents aresummarized as following:（1） Controlled synthesis and applications of hierarchical SnS₂micro/nano-structures.Different hierarchical SnS₂micro-/nanostructures were successfully synthesizedthrough an one-pot hydrothermal method by controlling the ratio of SnCl4andL-cysteine. The concentration of S^2-in the early stage is very important to thesysnthesis of hierarchical SnS₂micro/nano-structures. The chemical composition,crystalline property, building blocks, assembling format and porous structure ofthe hierarchical SnS₂micro/nano-structures can be affected by the concentration of L-cys. And they have great effects on the lithium storage, optical, photoelectricresponse, photocatalysis and adsorption properties of these hierarchical SnS₂structures.（2） Hydrothermal synthesis and optical properties of SnS₂intercalationcompounds.It is general, facilate and economic that introducing hydrothermal method to thedirect synthesis of SnS₂intercalation compounds. The intercalated objects can besurfactants or polymers, such as CTAB, SDBS, PVP and PEG. The formation ofSnS₂intercalation compounds can be controlled by thermodynamics and affectedby the molecue weight and concentration of intercalated objects, reactiontemperature, reaction time and the release rate of S^2-. The PEG intercalated SnS₂can be easily exfoliated to single layer of PEG-SnS₂QDs by solvent underultrasonication. These QDs have strong fluorescence with a quantum yield of65%and can be affected by the molecule weight of PEG and the concentrationsof precursors.（3） Synthesis and lithium storage properties of SnO_xS_2-x/GNS composites.Two types of composite with different ratios between SnO₂and SnS₂(SnO_0.6S_1.4/GNS and SnOS/GNS) have been synthesized by ultrasonication.Electrochemical measurements show both composite can realize the fullyreversible lithium storage of tin based chalcogenide. The key reasons may beattribute to the GNS composite and mixed phase of SnO₂and SnS₂, which dopedwith each other in the nano-level. The ratios between SnO₂and SnS₂can greatlyaffect the lithium storage performances and SnOS/GNS exhibited respectivelygood cycling performance （0.2A g-1,1066mAh g-1after40cycles） and ratecapability （2A g-1,402mAh g-1）.（4） Hydrothermal synthesis of hierarchical SnO₂micro-/nanostructures.Divers SnO₂structures, such as hollow microspheres, nanoparticles, nanorodsand urchin-like hierarchical micro-/nanostructures are synthesized though amercaptoacetic acid assisted hydrothermal method by controlling alkali types.Gas sensors based on hollow microspheres and urchin like structures haveextremely high sensitivity to alcohol, and the sensitivity of100ppm ethanol ofurchin like structures can reach to73.7. SnO₂nanorods array/GNS composite canbe synthesize by adding graphene oxide to the reaction system of urchin likestructures. And the composite show superior lithium storage properties （0.2A g-1,63cycles,1154.1mAh g-1）. The high performance can put down to the layered porous structure of graphene nanosheets with in-situ growth SnO₂nanorodsarray。...