Preparation And Electrochemical Properties Of Reduced Graphene Oxide/Manganene Dioxide Composites For Supercapacitor

Supercapacitor, as a new type of energy storage, is receiving significant attention,mainly due to its high power density and long lifecycle. The electrode materials forsupercapacitor are often classified into three types, i.e., carbon-based materials, metaloxide materials and conductive polymer materials, among which Graphene and manganesedioxide (MnO2) are one of the focuses. Combining different materials to form a compositewas recognized as smart strategy to utlize the synergistic effect of individual material.However, the routines reported were usually long and complicated, and the nature of theprecursor for the composites was not fully utilized. So, in this article, we reported a novelone-step routine to prepare reduced graphene oxide/MnO2(rGO/M) composites from GOand Mn2+solution. The structure and morphology of composite and its components wascharacterized by of X-ray diffraction (XRD), fourier transform infraredspectroscopy(FTIR), Raman spectroscopy and thermal gravimetric (TG) analysis and fieldemission scanning electronic microscope (FESEM), the electrochemical propertiesinvestigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemicalimpedance spectroscopy techniques.Firstly, low-temperature reduced graphene oxide (lrGO) was prepared via low-temperature heat treatment, and used to investigate the effect of the load pressure and thetype of aqueous electrolyte on electrochemical properties of lrGO electrode. The resultsshowed that the best specific capacitance was obtained at a load pressure of10MPa, andH2SO4as electrolyte was benefiter for improveing specific capacitance than Na2SO4.Secondly, rGO/M composites were successfully prepared via one-step hydrothermalroutine, for which oxide functional groups of GO were used as a oxidant and Mn2+as Mnsource. The results showed that rGO had folded flake structure, attached with small andscattered MnO2particles of30~60nm. rGO/M composites exhibited high specificcapacitance, ratio characteristics and cycle stability. In the optimal case, a specific capacitance of277F/g could be obtained in1mol/L H2SO4at a current density of1A/g,with capacitance retention of98%after500cycles. Even for the scan rate of50mV/s, aspecific capacitance of173F/g can be still obtained.