This research was performed to study the anode reaction in a molten carbonate fuel cell. Chronoamperometry experiments and impedance measurements were carried out at gold and nickel flag-type electrodes in a 62 mole percent (m/o) Li{sub 2}CO{sub 3}/38 m/o K{sub 2}CO{sub 3} eutectic carbonate mixture at 923 K as a function of gas composition (H{sub 2}/CO{sub 2}/H{sub 2}O), and as a function of temperature between 823 and 1073 K. The i {minus} {radical}t extrapolation technique, generally applied to evaluate chronoamperometry results, is shown to yield systematic errors for the hydrogen oxidation studies in molten carbonates. A direct fit of the Gerischer-Vielstich relation yields more reliable results for gold. The current responses on Ni cannot be described by the Gerischer-Vielstich relation. The high reaction orders for hydrogen (0.7 to 1.0), medium for carbon dioxide (order 0.5), and the low or even negative reaction order for water (0 to {minus}0.25), indicate the hydrogen oxidation follows a Volmer-Heyrovsky-type mechanism on gold flag electrodes. The reaction rate at a nickel electrodes was found to be too high to be studied accurately using impedance measurements and chronoamperometry on flag electrodes. In spite of the poor accuracy reaction orders indicate that a final chemical reaction ismore » the rate-determining step in the reaction mechanism on nickel. The activation energy for the exchange current density was found to be in the order of 80 kJ/mol with a tendency to be higher for the gases richer in hydrogen. The activation energy for the Warburg coefficient (diffusion) was found to be about {minus}15 kJ/mol.« less