Synthesis, Characterization And Properties Of In₂S₃Nanosheets And Their Nanocomposites

In this thesis, our work maily aimed at the large-scale synthesis of the nanostructured materials and their practical application in rechargeable lithium-ion batteries anodes and photocatalysis. By experimental design and investigations, we successfully fabricated the hexagonal In2S3nanosheets, graphene-based In2S3composites and one-dimnension-like Ag@In2S3heterostructures. Besides, we also investigated the lithium-ion storage when the three nano structured materials were applied as anodes in rechargeable lithium-ion batteries, respectively. In addition, the photocatalytic activity of hexagonal In2S3nanosheets was also investigated. The main results are summarized as follows.(1) Successfully fabricated hexagonal In2S3nanosheets with large BET surface area via a simple hydrothermal route. Through SEM、TEM and HRTEM observations on as-prepared samples, we found that the nanosheets are loose attachment and their thickness is about5nm. Systematic trials show that solvent and surfactant play very essential roles on the final morphologies and structure of as-prepared samples. The experimental results show that Hexadecyl trim ethyl ammonium Bromide (CTAB) was removed or substituted by sodium dodecyl benzene sulfonate (SDBS), the uniform hexagonal In2S3nanosheets were not obtained at all. Besides, the ethonal used as part solvent made the final product hexagonal structure and flower-like morphology. Finally, when the nanosheets used as an anode and charged/discharged at a current density of700mA/g, the specific capacity of composite can retain at about450mAh/g after40cycles. The layered structure, large BET surface area and loosely attached nanosheets lead to the high specific capacity.(2) The as-prepared hexagonal In2S3nanosheets exhibit excellent photocatalysis. When these nanosheets was used to degrade Methylene Blue (MB) aqueous solution under irradiation of visible light,15mg In2S3nanosheets can degrade95%MB. However, at the same condition, the flower-like In2S3nanomaterials can only degrade60%MB. The difference of BET surface area between them contributes to different activity of degradation.(3) Successfully fabricated the sheet-on-sheet graphene-based IN2S3composites via one-step method. Through SEM、TEM and EMP observations on as-prepared samples, we found that In2S3sheets were uniformly dispersed on the graphene sheets. Furthermore, the Raman and XPS measurement revealed that the Graphite Oxide (GO) was reduced because of thioacetamide. The intrinsic layered structure, enhanced BET surface area and excellent conductivity of composite contribute to improvement of lithium storage. When the composite was applied as a anode in lithium-ion battery and charged/discharged at a current density of100mA/g, the specific capacity can retain at1000mAh/g after100cycles, and the Coulombic efficiency exceeds99%. When the electrodes were run at a current density of500mA/g, a stable specific capacity value can be retained and an enhanced life of cell can be observed. Besides, the method to fabricate the reduced graphene oxide-β-In2S3(RGO-In2S3) composite electrodes is able to be used to prepare the other grapheme-based nanomaterials, e.g. CuS, MoS2and FeS, and so on.(4) Successfully synthesized a novel Ag@In2S3heterostructure composite. Through SEM, TEM and EMP observations on as-prepared samples, we found this novel heterostructure consists of Ag nanowires and In2S3nanosheets grown coaxially on Ag nanowires. The XRD data revealed that the composite was made up of cubic Ag and hexagonal In2S3. Finally, we investigated the electrochemical performance when this one-dimension-like heterostructure applied as anode in lithium-ion battery, and found that the electrochemical reaction process of Ag@In2S3electrode agrees with that of In2S3nanosheets electrode, showing electrochemically inactive Ag nanowires. And when the Ag@In2S3electrodes charged-discharged at a current density of700mAh/g, the specific capacity shows apparent improvement as compared with that of the pure In2S3electrode. In addition, charged/discharged at a current density of200mA/g, the specific capacity can retain at about700mAh/g and the value is quite stable upon cycling. Good conductivity of Ag nanowires and corn-like stable structures upon cycling lead to the excellent performance of lithium-ion storage. Such findings suggest that it will be a new solution to fabricate new electrode materials.