This paper presents the direct synthesis of highly porous carbons via the carbonization of potassium humate in inert atmosphere without any activation. Carbonization temperature is important for carbon structures and their electrochemical performance in electric double-layer capacitors. The CK800 material derived from potassium humate has a high-specific surface area of 890 m(2) g(-1) and an ideal average pore size of 2.56 nm. The CK800 material can also deliver a high-specific capacitance of 232 F g(-1) (26.1 A mu F cm(-2)) at a constant charge/discharge current of 0.5 A g(-1). This capacitance is maintained at a value of 114 F g(-1) (12.8 A mu F cm(-2)) at 30 A g(-1). This material also has good cycle stability with over 93.5 % capacitance retention after 5000 cycles when measured in a three-electrode system using 6 M KOH as electrolyte. In this study, the CK800 material is tested in a three-electrode system using 1 M NaHCO3 as electrolyte. Operational voltage in 1 M NaHCO3 aqueous solution could be extended up to 1.3 V.