This is the first report of KCl templated carbon preparation from walnut shell. Activated carbon (AC) with high specific surface area (1958 m(2) g(-1)) was obtained by CO2 activation of KCl templated biochar at 900 degrees 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 Omega. 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)).