Preparation And Electrochemical Properties Of Conducting/Graphene Composites

Graphene, as a new carbon material, with high specific area, carrier mobility, mechanical strength, and thermal stability, has great prospects in the field of new energy materials, sensors, catalysis, optical and so on. Graphene oxide is the derivative of graphene, it has a large amount of oxygen functional groups such as epoxy group, carboxyl group, hydroxyl group on the basal plane or eges. The polar oxygen functional groups of GO render it strongly hydrophilic, expanding its applications. The preparation and electrochemical properties of graphene/conducting polymer composites were carried out in this paper. Conducting polymer have many advantages such as high storage capacity, reversibility, but during the charging/discharging process it may occur swell and shrink phenomenon, which leading mechanical degradation of electrode and fading electrochemical performance. It was demonstrated that conducting polymer composites could meet the challenge. This paper states three sections:(1) According to the literature, graphene oxide has the oxidative ability. This paper took advantage of the oxidative property of GO, successfully prepared polypyrrole/grphene (PPy/GO) composite by using graphite oxide(GO) as the oxidant. The results showed that polypyrrole was synthesized via in situ polymerization in the presence of graphene oxide. Graphene oxide was separated into single layer, increasing the specific surfaces of the composites. The PPy/GO composite exhibited the specific capacitance of 695.5 F/g at a current density of 0.5 A/g, which was absolutely higher than pure polypyrrole. And the composites showed a retention of 70.2% of its initial capacitance after 500 cycles at a current density of 0.5 A/g.(2) Polyaniline/graphene (PANI/GO) composites were successfully prepared via in-situ chemical oxidative polymerization of aniline monomers by using graphite oxide (GO) as the oxidant. It was found that aniline monomers absorbed on the surface of graphene layers carried out the polymerization, obtained a "sandwich" structure composites. The composites showed considerable electrochemical properties. When the mass ratio of aniline to graohene was 5:1, the specific capacitance of the composites reached 624.2 F/g at a current density of 0.5 A/g, which is much higher than pure PANI; The retention rate was 79.6% after 500 cycles, showed good cycle stability.(3) The above reported the conducting polymer/graphene composites connected by π-π; And this section proposed a method to prepare the composites covalently connected by an anamide group. The electrochemical properties were studied in this literature. It was found that when the mass ratio of anline to gaphene oxide was 10:1, the specific capacitance was 250 F/g at a current density of 0.5 A/g. The specific capacitance was decline after the reduction of composites may due to the structure of the doped polyaniline composites were destroyed. The retention rate was 90.5% after 500 cycles, showed better cycle stability.