A porous hydrous ruthenium oxide for supercapacitors is fabricated by electro-deposition accompanied with hydrogen-evolution reaction. This high-surface-area electrode (207.5 m(2) g(-1)) is developed by electrochemical de-alloying process of copper from as-deposited Ru-(Cu) foam (23.5 m(2) g(-1)). The threedimensional structures with open pores and numerous dendritic morphologies produce good electrochemical performances by providing the pathway for facile penetration of electrolytes into active electrode surface. The three-dimensional porous hydrous ruthenium oxide exhibits good capacitance performance of 809 F g(-1) at 1.5 A g(-1) high energy density (112 Wh kg(-1)), and excellent stability retention (similar to 98%) even after 3000 cycles. (C) 2012 Elsevier B.V. All rights reserved.