Model interpretation of electrochemical impedance spectroscopy and polarization behavior of H-2/CO mixture oxidation in polymer electrolyte fuel cells

A mathematical model is proposed based on electrode kinetics analysis for t he oxidation of 2% CO + H-2 mixture in polymer electrolyte fuel cells. Succ essful simulation of the polarization curve and experimental impedance spec tra for Pt/C electrode system confirm the validity of the model which shows that the impedance is strongly dependent on electrode potential. With the increase of potential, an inductive behavior will occur. It is believed tha t the appearance of this inductive pattern can be used as a criterion for t he onset of CO oxidation by the coincidence of the potential at which induc tive behavior occurs with the ignition potential for CO oxidation. The effe cts of change of CO oxidation rate constant and CO adsorption equilibrium c onstant on impedance pattern, as well as on CO surface coverage and Faradai c current are also delineated with the use of the proposed model. (C) 2001 Elsevier Science Ltd. All rights reserved.