Oxygen Exchange on Platinum Electrodes in Zirconia Cells: Location of Electrochemical Reaction Sites

Abstract

Oxygen exchange kinetics on porous platinum electrodes in a zirconia electrochemical cell were measured at 600°-800°C in 10-5-0.21 atmospheres oxygen. Steady-state polarization and potential-step chronoamperometric experiments were performed. Steady-state current-voltage characteristics exhibited near-exponential behavior at intermediate potentials and approached anodic and cathodic limiting currents at higher overpotentials. At and below 600°C, the initial decay of the current following anodic and cathodic potential steps was inversely proportional to the square root of time. This Cottrell-type behavior indicates that the charge-transfer step in the mechanism of oxygen exchange occurs at the three-phase boundary where the electrode, electrolyte, and gas-phase intersect. © 1990, The Electrochemical Society, Inc. All rights reserved.