Polyaniline (PANI) nanofibres are synthesized by interfacial polymerization and their electrochemical performance is evaluated in an aqueous redox supercapacitor constituted as a two-electrode cell. The initial specific capacitance of the cell is 554 F g(-1) at a constant current of 1.0 A g(-1), but this value rapidly decreases on continuous cycling. In order to improve the cycleability of the supercapacitor, a composite of polyaniline with multi-walled carbon nanotubes (CNTs) is synthesized by in situ chemical polymerization. Its capacitive behaviour is evaluated in a similar cell configuration. A high initial specific capacitance of 606 F g(-1) is obtained with good retention on cycling. In both supercapacitors, the effect of charging potential on cycling performances is investigated. (c) 2007 Elsevier B.V. All rights reserved.