An asymmetric supercapacitor with improved energy and power density, relative to a symmetric Ru oxide device, has been constructed with anthraquinone-modified carbon fabric (Spectracarb 2225) as the negative electrode and Ru oxide as the positive electrode. The performance of the supercapacitor was characterized by cyclic voltammetry and constant current discharging. Use of the anthraquinone-modified electrode extends the negative potential limit that can be used, relative to Ru oxide, and allows higher cell voltages to be used. The maximum energy density obtained was 26.7 Wh kg(-1) and an energy density of 12.7 Wh kg(-1) was obtained at a 0.8 A cm(-2) discharge rate and average power density of 17.3 kW kg(-1). The C-AQ/Ru oxide supercapacitor requires 64% less Ru relative to a symmetric Ru oxide supercapacitor. (C) 2008 Elsevier B.V. All rights reserved.