In this paper, we investigate the kinetics of the H-2/CO electro-oxidation reaction on Pt/C catalysts by using a combination between an equivalent electrical circuit (EEC) fitting method and a mathematical model based on the faradaic impedance of irreversible electrode reactions. After the theoretical derivation of the faradiac impedance expression and the correlation of these electrochemical parameters to the EEC parameters, the experimental EIS data is fitted to obtain the elements in the EEC. The kinetic parameters of the multi-step electrode reaction are then extracted from the definitions of the electrochemical parameters by further mathematical manipulation. Finally, this method is validated by a comparison between the simulated results and the experimental data, which demonstrates its good applicability. (C) 2004 Elsevier Ltd. All rights reserved.