CYCLIC VOLTAMMETRIC CHARACTERIZATION OF ORIENTED MONOCRYSTALLINE GOLD SURFACES IN AQUEOUS ALKALINE-SOLUTION

Monocrystalline gold surfaces having five different crystallographic orientations have been characterized by means of cyclic voltammetry in aqueous 0.11 M NaOH in order to examine the electrochemistry of oxide formation and removal in comparison with the well-characterized behavior in acidic media. For the higher-index faces Au(210) and (311), these voltammetric features in 0.11 M NaOH are closely similar to those observed in acidic electrolytes, although the occurrence of substantial OH- adsorption is signaled by a broad reversible current-potential feature at less positive potentials. For the low-index faces Au(100) and (111), however, the voltammograms in 0.11 M NaOH differ substantially from those in acid. These differences are ascribed to the influence of potential-dependent OH- adsorption, which overlaps with oxide formation and especially reduction, and attendant potential-induced surface reconstruction. The behavior of Au(110) is intermediate between that of these other two low-index and the higher-index faces. As for the voltammetric features in acidic electrolytes, such crystal face-dependent voltammetry in 0.11 M NaOH can be employed as a sensitive (albeit empirical) check of the chemical and physical state of the interface prior to other electrochemical measurements. © 1990.