Impedance studies on direct methanol fuel cell anodes

The processes taking place in direct methanol fuel cell anodes are characterized by ac impedance spectroscopy. Under conditions of practical interest, i.e., low methanol stoichiometry factors, the kinetic and the mass-transport resistance give rise to two well-resolved semicircles in the Nyquist plot. When mass-transport limitations are excluded, inductive loops occur in the complex plane which are interpreted in terms of the most widely accepted reaction mechanism for methanol electrooxidation. A simple equivalent circuit is used to model this impedance behaviour.