▎ 摘　　要

Nanocomposites of partially reduced graphene oxide (GO)-K2Mn4O8 were synthesized via a hydrothermal process at different temperatures and molar feed ratios of GO to KMnO4. X-ray diffraction (XRD) analysis confirmed that both alpha-MnO2 and a novel crystal phase of K2Mn4O8 were obtained under the investigated hydrothermal conditions. X-ray photoelectron spectroscopy (XPS) revealed diverse changes of the oxygen-containing functional groups on the surface of GO depending on temperature and molar feed ratio. The microstructure of the composites was studied to help understand their electrochemical properties. A flaky structure of reduced graphene oxide (rGO) covered by nanoparticles was observed by scanning electron microscope (SEM), which was considered to be favorable for charge transfer. The capacitive properties of the composites were compared using cyclic voltammograms and galvanostatic charge-discharge measurements. The specific capacitance of the optimal sample was calculated to be 251 F . g(-1) with an energy density of 32 Wh . kg(-1) and a power density of 18.2 kW . kg(-1) in 1 mol . L-1 Na2SO4 electrolyte at a current density of 1 A . g(-1) between 0 and 1 V. Moreover, the capacitance retention ratio of this sample remained at 88% after 1000 cycles at a high current density of 5 A . g(-1).