The Polarization of Molten Carbonate Fuel Cell Electrodes: II . Characterization by AC Impedance and Response to Current Interruption

Abstract

AC impedance and current interruption measurements have been investigated as an in situ method for characterizing rate‐limiting processes in molten carbonate fuel cell porous electrodes. Analysis of the data for the fuel cell anode indicates that the anode is always under strong mass‐transfer control, in the temperature range of 600–700°C. Analysis of data for the cathode indicates that at 650°C the cathode is under mixed control. Charge‐transfer control is approached at lower temperature (600°C) and at high partial pressures. Control by mass transfer or slow homogeneous reactions (e.g.,) in the cathode tends to become dominant at higher temperature (700°C). The kinetic (exchange) reaction orders of the cathode reaction are approximately 0.85 and −0.45 for oxygen and carbon dioxide, respectively. The activation energy of oxygen reduction is approximately 230 kJ/g mol.