KINETICS OF OXYGEN REDUCTION ON FULLY AND PARTIALLY IMMERSED PT, PD AND AU ELECTRODES IN AN NACL+KCL EUTECTIC MELT

The kinetics of the O2-/1/2O2 (Pt, Pd, Au) electrode in an NaCl + KCl eutectic melt at 1023 K was studied using the galvanostatic double-pul se and ac impedance methods. The cathodic reduction of oxygen proceeds via a two-step mechanism, and the rate of the rapid charge-transfer s tep was found from the galvanostatic double-pulse measurement to be of the order of 10(4) A m-2. The exchange current density obtained from the ac impedance method was one order of magnitude less than that obta ined from the galvanostatic double-pulse method and probably correspon ds to that of the slower reaction step. The cathodic polarization curv es of the partially immersed O2-/1/2O2 electrode exhibit an exponentia l form at a low concentration of oxide ions. The polarization behavior was well explained by a model in which the role of the reaction produ ct (the oxide ion) on reaction kinetics was considered.