Synthesis Of Porous Graphene/PANI Composite Film(prGN/PANI) And Its Electrochemical Performance

Supercapacitor is a new type of environmentally friendly energy storage device between traditional capacitors and rechargeable batteries. Because of its high emergy/power density, fast charging-discharging rate and long-term cycle life, in recent years, supercapacitor has attracted more and more interests of researchers. However, the electrochemical performance of supercapacitors is highly dependent on the performance of electrode materials. So much effort has been focused on developing new electrode materials whih high performance and novel structure. PANI is one of the most promising used electrode materials for supercapacitors among conducting ploymers because of its enviromenetal and chemical stability, easy of synthesis, high conductivity, reversible redx states and high theoretical specific peseudocapacitance. However, the volume of PANI suffers from swelling and shrinkage during charging-discharging process, resulting in the poor cycling stability. In orders to overcome those limitations, hybrid composites combine PANI with graphene have been developed. Graphene has many special properties, such as high electrical conductivity, high theoretical specific area and superior mechanical properties. However, the suface area of graphene cannot be fully utilized due to the aggregation of graphene. In addition, the electrode material with high order structure is good for imporving the utilization of electrode material. 3D rGN/PANI composite film and 3r GN/PANI-NW composite film were fabricated successfully based on analysis above. The main studies were as follows:(1) Graphite oxide(GO) was prepared by a modified Hummers method. Reduced graphene(r GN) suspension was synthesized by electrostatic stabilization method with hydrazine and ammonia. Then PS/r GN film was obtained by vacuum filtration of a well-dispersed aqueous colloidal solution of rGN and PS. At last, PANI nanowires were grown on the the PS/r GN film by dilute polymerization procedure, followed by removing the PS to obtain 3D rGN/PANI composite film. The microstructures and morphologies of 3D rGN/PANI were investigated by FE-SEM,FT-IR,XPS and BET measurements. The electrochemical properties of the 3D rGN/PANI were characterized by CV, galvanostatic charge-discharge technique, electrochemical impedance spectroscopy and cycle stabilities tests. Result have shown 3D rGN/PANI film in a 3D porous structure and PANI nanowires array grow not only on the outer surface but also on the interior surface of the composite film. Moreover, a strong ? electron interaction between 3D r GN and PANI nanowire is existed. This novel structure can significantly increase the active surface area of electrode; provide high interfacial area, short ion diffusion path, and fast electrical pathways. Compared with rGN, 3D rGN, and pure PANI, 3D rGN/PANI film have more excellent electrochemical performance. The specific capacitance of 3D r GN/PANI film can achieve a maximum value as high as 740 F g-1 at a current density of 0.5 A g-1 and the capacitance retention is 87% after 1000 cycles at 10 A g-1, which display excel ent electrochemical performance.(2) Based on the results(1), polyaniline nano-wrinkles arrays on three-dimensional graphene film(3r GN/PANI-NW) by electropolymerization, which using polystyrene microsphere(PS) as sacrificial templates to form porous structure and ZnO nanorods as scaffolds to form PANI nano-wrinkles. The resulting 3rGN/PANI-NW with large surface area and well-defined pore structure and PANI nano-wrinkles arrays on the surface of the graphene film which can increase electrochemical activity and fast electron transfer between these two components. Electrochemical tests show that the maximum specific capacitance of 3rGN/PANI-NW is as high as 630 F g-1 at current density of 0.5 A g-1 and the cycling stability of 3rGN/PANI-NW composite material exhibits a high stable and 90.5% of the specific capacitance can still be retained after 5000 cycles. Moreover, the coulombic efficiency remains as high as 94.8% after 5000 continuous cycles. Therefore, the outstanding electrochemical performances may render this 3rGN/PANI-NW a high promising electrode material for high performa nce supercapacitors in practical application.