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Micro-porous activated carbons (ACs) with a narrow pore size distribution of 0.4-0.6nm and high specific surface areas (1160-1315 m2 · g-1 are prepared from environment-friendly, low-grade potassium humate (HA-K, carbon resource) and mild activating agent potassium acetate (CH3COOK). Microstructure characterizations indicate that the introduction of activating agent CH3COOK is a key step to achieve high specific surface area and carbonization degree. These ACs contain small amount of oxygen and nitrogen, and show obvious pseudo-capacitance besides double layer capacitance. As a result, the optimized ACs achieve high specific capacitances of 311F·g-1 and 317F·g-1 at 0.1A·g-1 in 2M KOH and 1M H2SO4 aqueous electrolytes, respectively. This sample also shows a good charge-discharge cycling stability within 10 000 cycles. [ABSTRACT FROM AUTHOR]