LAUSR

Abstract This is the first report of KCl templated carbon preparation from walnut shell. Activated carbon (AC) with high specific surface area (1958 m2 g−1) was obtained by CO2 activation of KCl templated biochar at 900 °C. The electrochemical properties were evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. WS-90 had relatively low inner resistance of 1.7 Ω. The specific capacitance was 245.0 F g−1 in 6 mol L−1 KOH electrolyte at a current density of 0.1 A g−1, and it can maintain very good cyclic stability with capacitance retention ratio of 95.4% (from 245.0 to 233.7 F g−1 at current density of 0.1 A g−1 after 4000 cycles (0.1, 0.5, 1.0 and 5.0 A g−1 for 1000 cycles, respectively)).