| Due to its unique structure of one carbon atoms thickness with 2D layer and excellent properties of electrocity, machanics, optics, thermology, Graphene has a great application prospect in field effect transistor, sensor, transparent conductive films, and electrochemical energy storage. However, there are several disadvantages, such as environmental pollution, the fussy and time-consuming, during the process for large scale preparation of graphene. Those problems are critical and have to be faced and resolved urgently. So it is very important to develop a low-cost and environment-friendly route for the producing of graphene and grapene-based materials. In the present thesis, a highly atom-ecomonic method was proposed to synthesize graphene/MnOx copmposite and the graphene/Mn3O4 composite aerogels (GSA/Mn3O4) used graphene oxide/MnSO4 (GO/MnS04) made by modified Hummers method as the reactant combining the technology and method of coprecipitation,thermal reducition and hydrothermal reduction et al. The performance of the composites as supercapacitor and lithium ion batteries was measured. The green synthesise of graphene/sulfur composite was achieved used GO as oxygenant and carbon precursor and the H2S as reductant and sulfur precusor based on the mechanism of selective reduction under the assist of H2O2. The performance of the graphene/sulfur composite used as the anode was measured. Some progresses in the thesis are briefly summarized as follows.A by-product free strategy based on modified Hummers method was proposed to synthesize coal-derived graphene/Mn3O4 composites without any additional manganese source. TaiXi anthracite coal was used as carbon source instead of conventional natural graphite flakes and MnSO4 produced from the modified Hummers was in situ transformed into Mn3O4 used KOH as precipitant in air. After reduction with hydrazine, the Mn3O4/reduced coal-derived graphene oxide (RCDGO/Mn3O4) was obtained and employed as the electrode material for the supercapacitors. In addition, K2SO4 produced from the modified Hummers was used as electrolyte, as a result, residual-free was achieved during the whole process, and the atom utilization was calculated as high as about 97%. A maximum specific capacitance of 260 F g-1 was achieved for RCDGO/Mn3O4 composite with 86% Mn3O4 at the currrent density of 50 mA g-1 in saturated K2SO4 electrolyte solution. The good capacitance retention (92-94%) was also observed after 1000 continuous cycles of galvanostatic acharge-discharge at the current density of 2 A g-1. The method successfully resolved the problems, for example environmental pollution, time-consuming et al. Furthermore, it was proved that anthracite coal is a good candidate for the synthesis of graphene and graphene-based composites with novel structures and various applications.GO/MnSO4 from the modified Hummers method has been in situ transformed into graphene/MnO hybrid materials without additional manganese via precipitation combined with hydrogen and ammonia reduction. The nitrogen doping graphene/MnO (N-GS/MnO) was synthesized by thermal reduction in the ammoina atomosphere, respectively. The specific capacity of N-GS/MnO was 987 mAh g"1 at the current density 100 mA g-1. Because of the existence of the pyridinic nitrogen and the lower resistance, the N-GS/MnO composite used as the negative electrode material for lithium ion battery showed good performance.The GSA/Mn3O4 was synthesized by the hydrothermal method using the GO/MnSO4 suspensition as the reactant under the assist of the ammonia. The performance of the GSA/Mn3O4 as the negative electrode material for the lithium ion battery was explored. The GSA/Mn3O4 possessed more abundant pore structures than that of powder samples and three dimensional channel connected. The GSA/Mn3O4 with the Mn3O4 percentage of 70 wt.% has the excellent performance, and its specific capacity was 1112.6、789.3、650.9、475.5 mAh g-1 at the current density of 100、400、800、1600 mA g-1, respectively. The specific capacity of 593 mAh g-1 was still retained even after continue 100 cycles at the current density of at 800 mAg-1.The graphene/sulfur composite (GS/S) was successfully synthesized based on the selective reduction mechanism. During this synthesis process, the GO acted as the oxidant and carbon precursor, the H2S was used as reductant and sulfur source, the H2O2 was used as the additonal oxidant. The percentage contant of sulfur in the GS/S could be controlled by the changing the addition of H2O2. The structure character and the performance used as the cathode material for the lithium-sulfur battery of the GS/S were studied systematically. The study showed that the element sulfur was distributed uniformly on the surface of the graphene in amorphous sulfur forms. Based on the total mass of the composite, the GS/S with the sulfur content of 70 wt.% has the highest specific capacity than that with other sulfur content. The discharge specific capacity of GS/S-70 was 570、440、377、332、274 mAh g-1 at the current density of 0.2、0.5、1.0、2.0、5.0 A g-1, respectively. |
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