Double layer supercapacitor properties of onion-like carbon materials

This paper describes the electrochemical performance of carbon onions as electrode materials in electrical double layer capacitors with water electrolytes. Onion-like carbon (OLC) species were produced by vacuum annealing of detonation nanodiamonds (NDs) powder at 1170-2170 K. The material capability of the charge accumulation in the electric double layer was estimated using the voltammetric technique. The correlations between specific capacitance, surface area and conductivity were found. Charge-discharge measurements revealed a dependence of the specific capacitance of OLC on the degree of diamond particle graphitization and defectness of particle surfaces. Promising capacitance values, ranging within 20-40 F g(-1) and within 70-100 F g(-1) were found for the OLC materials operating respectively in acid electrolytic solution (1 M H2SO4) and alkaline electrolytic solution (6 M KOH). (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim