Hierarchically Multi-functional Graphene: Preparation And Application As High Performance Electrode Materials

Graphene is new two-dimensional material with unique structure. In2004,Professor Andre Konstantin Geim with his teamwork first got exfoliated graphene fromHOPG (Highly oriented pyrolytic graphite). Before that, both theory and experimentsuggest that perfect two-dimensional crystals can not exist at T≠0K. Graphene, asingle-layer two-dimensional carbon sheet with a hexagonal packed lattice structure,shows various unique properties in electronic, optical, mechanical and thermal fields,and thus becomes the hot research area in chemical and material sciences.Multi-functional composites based on graphene, not only show better performance thangraphene, but also have some unexpected performance, which extend its applications incatalysis, functional materials and energy. This thesis demonstrates their synthesis,properties and application of three-dimensional graphene foam prepared using aninnovative approach..This thesis has four sections: three-dimensional (3D) graphene, phosphorus doped3D graphene,3D graphene/ZnO nanorod composite, and phosphorus doped3Dgraphene/ZnO nanorod composite. Herein, we systematically studied the synthesismethod, characterization of morphology and electrochemical proprieties, andcorresponding results are listed as follow:1, Synthesis of3D graphene foam has been demonstrated using ethanol as thecarbon source, nickel foam as the catalyst and the template by chemical vapordeposition (CVD) method. Ethanol gas was generated by using a bubble method.3Dgraphene was synthesized at750oC. The as-synthesized3D graphene replicated thethree-dimensional network of Ni foam. Meanwhile, the electrical conductivity is as highas7.293×104S/m, and the specific capacitance is up to380F/g at the scan rate of5mV/s.2, Phosphorus doped3D graphene was synthesized by using nickel foam ascatalyst, as well as triphenylphosphine (TPP) as the carbon source and phosphorussource without using toxic organic solvents by CVD method. P content of assynthesized phosphorus doped3D graphene is2.91%. It is found that the onset potentialis-0.187V, and the current density only decreased12.59%after10000s, also exhibitedgood resistance to methanol. 3, We synthesized3D graphene/ZnO nanorod composite using hydrothermalmethod and discussed the relationship between structure and properties assupercapacitor electrode. Finally, we compared the performance between3D grapheneand3D graphene/ZnO nanorod composite. The as synthesized3D graphene/ZnOnanorod composite exhibited good capacitor performance of554.23F/g at the scan rateof5mV/s, and maintained94.4%of original capacitance after2300cycles.4, We synthesized phosphorus doped3D graphene/ZnO nanorod composite usinghydrothermal method and discussed the relationship between structure and properties assupercapacitor electrode. Finally, we compared the performance among3D graphene,phosphorus doped3D graphene and phosphorus doped3D graphene/ZnO nanorodcomposite as supercapacitor electrodes. The capacitance of phosphorus doped3Dgraphene/ZnO nanorod is up to341.11F/g.