Preparation Of Graphene/Poly (P- Phenylenediamine)/Metal Oxide Ternary Composites And Their Application As Supercapacitors

Supercapacitor is one kind of energy conversion and storage devices with high power density and long cycle life, but the extensive application is constricted by the relatively low energy density. Therefore, seeking for suitable electrode materials for supercapacitors has been a significant issue. Graphene is a typical carbon material owing to high theoretical specific surface area, good conductivity and mechanical stability, but its effective area and electrochemical properties are limited by easy stacking and agglomeration of graphene nanosheets. In contrast, metal oxides and conducting polymers possess higher specific capacitance, but high resistance and poor cycle stability also limit their utilization in supercapacitors alone. Hence, preparation of ternary composites by mixing these three components is considered as a feasible method to compensate all defects. In terms of ternary composites, graphene used as a scaffold plays a role in increasing the cycling stability and fastening the rate of charge transport, while the other two components offer higher capacitance and energy density. The main results are as follows.(1) Graphene oxide (GO) prepared by modified Hummers is used as a support for the synthesis of composites and poly (p-phenylenediamine) is selected as another fixed component. Meanwhile, different ternary composites can be obtained by changing the types of metal oxides and mass ratio of these three components and their relevant electrochemical properties are studied.(2) A new ternary composite containing graphene, tin oxide (SnO2) and poly (p-phenylenediamine) (PpPD) is prepared successfully via one-pot method. When the mass ratio of GO, SnCl2 and pPD is 1:2:8, the graphene/SnO2/PpPD composite achieves an enhanced specific capacitance (777.5 F·g-1) at 5 mV-s"1 and retains 97.8% of the initial capacitance after 2000 cycles. Furthermore, its corresponding symmetry supurcapacitor possessed the energy density of 19.51 Wh·kg-1 at a power density of 325 W·kg-1 and the maximum power density of 5.0 kW·kg-1 at a sharply reduced energy density of 4.33 Wh·kg-1.(3) A ternary graphene/MoO3/PpPD nanocomposite is successfully synthesized by selecting MoO3 nanorods as the third component, which can optimize the structure of composites and enhance the whole properties. When the feed ratio of GO, Na2Mo04 and pPD is 1:2:8, the resulting composite possesses a maximum specific capacitance of 1042.6 F·g-1 at 1 A·g-1 in a three-electrode system and the maximum energy density of symmetry supercapacitor is improved to 24.56 Wh·kg-1 at a power density of 325 W·kg-1.