Effect of chemical modification of graphite nanoplatelets on electrochemical performance of MnO2 electrodes

To improve wettability between electrode material and electrolyte for high-rate supercapacitor application, the surfaces of graphite nanoplatelets (GNPs) were chemically modified by concentrated acids. The functional groups were confirmed by Fourier transform infrared spectra (FTIR) and zeta potential measurement. The microstructures and morphology of composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical properties of the composites were characterized by cyclic voltammograms (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). At high discharge rates, the increase of specific capacitance of electrode material was primarily attributed to the improvement in wettability between electrode material and electrolyte, which came from the attached hydrophilic functional groups, resulting in rapid proton transport and more ion-accessible surface area.