Preparation And Capacitance Performance Of 3DGR/CNTs Composites

Supercapacitor is a kind of energy storage devices similar to battery in structure and manufacturing process,which is generally a sandwich structure composed of electrode materials,electrolyte and separator.Most researches of supercapacitor focus on electrode materials.The electrode materials of supercapacitor with excellent performance commonly own high specific surface area and porosity.Carbon materials are superior electrode materials among numerous electrode materials,and carbon nanotubes and graphene have become the research hotspots of carbon materials in the field of supercapacitor.In first part,carbon nanotubes@three-dimensional graphene?CNTs@3DGR?composite materials were fabricated employing Ni-Mg-Al ternary metal oxide?TMO?as catalyst substrate,and the influence of different preparation conditions on the capacitance properties were investigated.Firstly,TMO was synthesized by homogeneous precipitation method.Then,CNTs@3DGR were synthesized over the TMO by one-step chemical vapor deposition?CVD?method using CH₄ as carbon source and Ar as protective gas.The two-dimensional CNTs were grown on the in-situ reduced Ni nanoparticles,and the 3DGR were grown on the compound metal oxides of Mg and Al.After etching the metal oxides,the composite materials were obtained.The structure and performance of CNTs@3DGR were optimized by controlling the parameters during the precipitation of TMO and CVD reaction of CNTs@3DGR,such as molar ratio of metal ion,growth temperature,growth time,and methane flow rate.In second part,sandwich 3DGR/CNTs composites were fabricated by CVD template-directed method.Firstly,two pieces of defective graphene films?1×1 cm?were synthesized by CVD method,and then they were transferred to the both sides of foamy copper after etching substrate by the traditional basal corrosion method to achieve a sandwich structure template.Afterwards,carbon nanotubes grew on the sandwich template by CVD template-directed method to form sandwich 3DGR/CNTs composites.The influences of growth parameters on the structure were explored.However,the foamy copper cannot be directly used as current collector material due to poor chemical stability and easy corrosion.In addition,the transfer process of graphene film to two sides of the foamy copper may cause the damage of graphene films.Basing on above analysis,we replaced the foamy copper with nickel foam as current collector material and directly used 3DGR/CNTs with nickel foam as working electrode in the test of electrochemical performance.For the fabrication of 3DGR/CNTs,graphene were synthesized on nickel foam by CVD method,and then carbon nanotubes were grown by second CVD.Moreover,we adjusted the growth parameters of each stage for the composite materials and changed the surface treatment process to investigate the influence on the capacitance performance of the composite materials.The results of above experiments can provide a useful guide for structural design,composition modulation and performance optimization of 3DGR/CNTs composites.