Abstract: Three kinds of activated carbon samples with different specific surface areas are prepared from walnut shell by using the steam activation method under different activation time.The influences of activation time on morphology,physical characters and pore structure parameters of the samples are studied by means of scanning electron microscopy (SEM),Fourier transform infrared spectroscopy (FT-IR),X-ray diffraction (XRD) and N2 adsorption/desorption method.Electrochemical performances of the samples are evaluated through galvanostatic charge-discharge,cyclic voltammetry and so on.It is found that all three samples exhibit extraordinary rate performance under high current density (up to 20 A·g-1).As the activation time prolongs,specific surface area and capacitance as well as energy density of the samples increase,however their stability decrease.The sample (AC120) prepared over an activation time of 120 minutes has a reasonable pore size distribution and a surface area of 1 644 m2·g-1.In an organic electrolyte system,AC120 sample's maximum specific capacitance and maximum energy density is 83.8 F·g-1 and 18.2 Wh·kg-1,respectively.AC120 also shows better performance in reversibility and stability,thus making it most suitable in long-term utilization.
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