Cassava peel was used as the precursor for activated carbon-based electrodes which were then prepared by a combination of chemical and physical activation. The surface of the activated carbon was treated with the oxidative chemical agents, 98 wt.% H(2)SO(4), 65 wt.% HNO(3), and 30 wt.% H(2)O(2) solutions. The surface modification had no significant effect on the specific surface area, but greatly influenced the surface chemistry of the carbons. The presence of oxygen-containing groups increased the polarity and hydrophilicity of activated carbon, and thus improved the performance of the activated carbon-based electrode. As a result, the specific capacitance of the HNO(3) Modified AC-electrode reached 264.08 F/g, an increase of 72.6% compared to the original one. The results indicate that cassava peel waste can potentially be applied as a raw material for the production of low cost-high performance activated carbon electrode materials for Electric Double Layer Capacitors (EDLCs). (c) 2010 Elsevier Ltd. All rights reserved.