| Graphene is a kind of two dimensional carbon nanomaterials composed of the monolayer of sp2carbonatoms tightly packed in hexagonal symmetry. It has ideal lattice structure and possesses unique electrical,mechanical, optical and thermal properties, showing promising applications in nanoelectronic device,chemical/biological sensors, solar cells, supercapacitors, lithium-ion batteries and composites. To date,various methods including micromechanical exfoliation, chemical vapor deposition, epitaxial growth, andreduction of graphene oxide (denoted as GO) are available for preparing graphene. Among these methods,the reduction of GO has the features of easy processing, low cost, and high yield, showing great potentialfor large-scale preparation of grapheme. This approach, however, has drawbacks including incompletereduction reaction as well as liability of ultrasonically exfoliated graphene sheets to restack andagglomerate during the reduction process and successive drying process. Thus a liquid ammonia-alkalimetal system was adopted to reduce GO so as to increase the degree of reduction and mitigate theagglomeration of graphene by making use of the non-aqueous system. In the meantime, ultrasound-assistedreduction by hydrazine was adopted to prepare chemically reduced graphene oxide (denoted as RGO) andits composites with a high degree of reduction. The main research contents and results are as follows:1. Liquid ammonia was adopted as a solvent to exfoliate GO under assisted ultrasound irradiation, whileliquid ammonia-alkali metal with strong reducing ability was adopted to further intercalate and exfoliateGO and reduce GO as well. The micro-morphology, chemical structure and crystal structure of as-preparedproduct were analyzed by transmission electron microscopy, infrared spectrometry, and X-ray diffraction.Moreover, the electrochemical properties of as-prepared product as an electrode material of lithium-ionbatteries were evaluated. Results indicate that the re-agglomeration of graphene during thermal reduction process can be effectively avoided by introducing low temperature reduction system; as-obtained graphenesheets have a thickness of2~5nm and most of their O-containing species are eliminated. In the meantime,graphene obtained via the reduction by liquid ammonia-Li has a first discharge capacity of937.4mAh/gunder a current density of100mA/g, and its discharge capacity after50cycles rises from98.5mAh/g to104.6mAh/g under a current density of2000mA/g. This demonstrates that as-prepared graphene as ananode material of lithium-ion battery has good rate capability and good cycling performance as well.2. Nickel-graphene composites (Ni@graphene sheets, denoted as NGS) were obtained throughultrasonic assisted simultaneous reduction of graphene oxide and nickel precursor by hydrazine. The crystalstructure and chemical structure of as-prepared products were analyzed by X-ray diffraction and infraredspectrometry, and their electric conduction performance and electromagnetic properties were evaluated.Results indicate that hydrazine is able to simultaneously reduce GO and Ni2+in the presence of assistedultrasound irradiation. Ni is capable of inhibiting the agglomeration of graphene during the reductionprocess, while graphene in turn functions to prevent Ni spheres from agglomeration. As-obtained NGScomposites retain the large specific surface area of graphene and possess good electric conductionperformance, electromagnetic properties, electrochemical properties, adsorption capability for towardsorganic dyes, as well as good microwave absorbing performance, due to the incorporation of Ni.3. As-obtained NGS composites were coated with GO generating novel NGS@GO composites so as tofurther improve the adsorption performance towards organic dyes. The adsorption performance ofas-obtained NGS@GO composites towards organic dyes was primarily evaluated. It was found thatNGS@GO nanocomposites possess excellent adsorption performance for Rhodamine B, an organic dye. |
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