AC-SUPERIMPOSED-ON-DC CHARACTERISTICS OF FUEL-CELL ELECTRODE-REACTIONS .1. PARTIALLY SUBMERGED SMOOTH ELECTRODE

The ac-superimposed-on-dc impedance of oxygen reduction at a partially submerged smooth electrode has been measured and analyzed, to illustrate the potential of this method. Theoretical expressions for its application to multi-step electrode processes are presented and applied to experimental data for oxygen reduction in bulk molten carbonate. The question of how to fit impedance data to a physically meaningful equivalent circuit is considered, and the uncertainty in fitted circuit parameters due to accuracy limitations is discussed for this particular application. Consequences for the interpretation of impedance measurements at electrodes covered by thin electrolyte films, to be reported in part II, are briefly considered.