Electro‐Oxidation of Formaldehyde at Silver Anodes—Role of Submonolayer Hydroxy Complexes in Noble Metal Electrocatalysis

Abstract

Although silver electrodes in base apparently commenced oxidation at ca. 1.0V (RHE), reversible peaks of low magnitude were observed (as in the case of gold) at much lower potentials. The location of these peaks depended upon previous electrode pretreatment, but with a specimen preanodized at ca. 1.6V, which apparently resulted in oxygen penetration into the outer layers of the metal lattice, an increase in current was observed at ca. 0.2V on the anodic sweep with a reversible set of peaks (occasionally—again as in the case of gold—a poorly resolved doublet) at ca. 0.35V. Reactive organic species,e.g., , added to the solution commenced (anodic sweep) and terminated (cathodic sweep) their oxidation in this region: at slow sweep rates, ca. 10 mV s−1, a limiting rate of oxidization was observed at higher potentials—the value, as in enzyme‐catalyzed reactions, being proportional to reactant concentration at low values of the latter and virtually independent of concentration at higher values. The results, which are assumed to be relevant to noble metal electro‐oxidation processes in general, were interpreted in terms of a cyclic redox reaction at metal adatom sites; a quantitative interpretation of the kinetic behavior was provided.