Rice husks were converted into activated carbon by KOH activation, at temperatures between 400 and 900 degrees C and used in a two-electrode supercapacitor. The rice husks contain SiO2 nano-crystals surrounded by an amorphous carbon matrix. The activated carbons maintained their size and shape after the synthesis process and the ordering degree of carbon increased at elevated temperatures. The highest BET surface area of the activated carbons was around 3145 m(2) g(-1). Electrochemical properties of the studied samples were measured using a two electrode cell in 6 M KOH and 1.5 M tetraethylammonium tetrafluoroborate in acetonitrile. The material synthesized at 800 degrees C showed the highest gravimetric capacitance performance of 367 F g(-1) and 174 F g(-1) in aqueous and organic electrolytes, respectively. In contrast to the commercial activated carbons, rice husk activated carbon (RHAC), this material showed excellent high-power handling ability and electrochemical cycle performance, after 30000 cycles the capacitive value almost remained unchanged. (C) 2015 Elsevier Ltd. All rights reserved.