Preparation of High-Performance Graphene/MnO₂ Composite by Plant Biotemplate Method and Its Electrochemical Property

A graphene/MnO₂ composite was prepared after dipping a plant membrane, which was used as both a carbon source and a template, into the manganese chloride solution and then calcining twice. The micromorphology, phase composition and surface property of the composite were analyzed. Then the composite was pressed to be an electrode and the electrochemical property was measured by cyclic voltammetry and constant current charge-discharge tests. The results show that there was no graphene oxide in the graphene/MnO₂ composite. The graphene showed a lamellar structure with wrinkles on it, whose thickness was 1.449 nm; there were lots of MnO₂ particles with the size of 10-40 nm and loaded on the graphene. The BET specific surface area of the composite was 202.5 m²·g^-1 and the pore size was 5-30 nm. The composite had an excellent electrochemical reversibility with the specific capacitance of 245 F·g^-1, which was much higher than that of commercial carbon powder (25-26 F·g^-1) and synthesized graphene by the plant membrane calcination (45-50 F·g^-1).