Influence of Electrolyte Composition on Electrode Kinetics in The Molten Carbonate Fuel Cell

Abstract

Electrode kinetics of fuel oxidation on nickel and cobalt electrodes is dis- cussed for three selected molten carbonate mixtures. The measurements were made using a potential step technique. The highest exchange current values were found on nickel anodes in all melts, and the highest of these values were found in the melt comprised of 43.5 mole percent Li2CO3-31.5 mole percent Na2CO3-25 mole percent K2CO3. In this ternary melt the exchange current density on nickel varied from 78 mA/cm 2 for intermediate-BTU fuel to 22 mA/cm2 for low-BTU fuel at 650oC The exchange current density was found to have an electrochemical reaction order parameter at constant overpotential of around 0.25 for hydrogen, carbon dioxide, and water. Electrochemical performance of the two anode materials in the three melts is discussed, and a tentative reaction mechanism is suggested for the oxidation reaction.