Oxygen Adsorption on Gold and the Ce(III)∕Ce(IV) Reaction

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Abstract
In and in , “oxygen” uptake on Au electrodes begins at 1.25V vs. NHE. Using a roughness factor of 1.4, monolayer coverage (600 µcoul/cm2) is reached at 1.45V; a second monolayer is completed at 1.75V. Oxygen, once adsorbed, is removed at approximately 1.3V. Thus, the kinetic parameters of the Ce(III)/Ce(IV) reaction in and in can be obtained at oxygen coverages and , respectively. Apparent exchange current densities, , were obtained from low overvoltage data . The charge transfer coefficient, , was determined from the slope of plots of log vs. equilibrium potential. It is independent of oxygen coverage in the range indicated. The apparent rate constant, , was calculated from and in the range . Extrapolation of the data to yields . This change in can be interpreted as a change in the potential across the inner double layer which appears as a change in , . It appears that up to , oxygen adsorbs uniformly and is an excellent electronic conductor which simply serves as an extension of the electrode surface. The constancy of indicates no changes in the over‐all structure of the interface in this region.

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