Nitrogen-containing porous carbons with numerous micropores were fabricated by pyrolysing polyvinylidene fluoride (PVDF) membrane following potassium hydroxide (KOH) activation at 600-900 A degrees C for 2 h under N-2 atmosphere. The fabricated nitrogen-containing porous carbons have a large specific surface area of approximately 2289 m(2) g(-1), a certain nitrogen content of 1.35 at.% and a favourable hierarchical porous structure possessing a great number of micropores and a part of mesopores. The carbon materials exhibit high specific capacitance of 338 F g(-1) at 0.5 A g(-1) in a 6 M KOH and outstanding cycling property of 91.6% maintenance at 2 A g(-1) after 10000 cycles. An all-solid-state symmetrical supercapacitor with these as-prepared materials as electrodes can deliver energy densities of 21.9 to 10.4 W h kg(-1) at power densities from 700.8 to 12910.3 W kg(-1). To sum up, the as-obtained porous carbon is a type of potential electrode material for electrical double-layer capacitor.