Unravelling Current–Potential Curves for Au(111) Surface Oxidation in the Presence of Formate

This study uncovers the dominant voltammetric features of Au(111) surface oxidation in the presence of formate at scan rates of 10 mV s−1 and above. The surface oxidation currents are typically masked by the high currents of the formic acid oxidation reaction (FAOR). The presence of formate leads to voltammetric characteristics of Au(111) surface oxidation that are similar to those with (bi)sulfate or acetate, suggesting a common mechanism of Au(111) surface oxidation in the presence of specifically adsorbing oxyanions. This mechanism involves a sequence of surface oxidation processes occurring at surface defects and on terraces. The process of surface oxidation typically commences at monoatomic high steps. Subsequently, the terraces undergo oxidation, which can be described by two additional processes including both adsorption and phase formation via nucleation and growth. The impact of defect density on the voltammetric characteristics of surface oxidation can be modelled and visualized. The simulated voltammograms show features that are well-known for systems such as Au(111) in the presence of (bi)sulfate. These findings contribute to a more profound understanding of the surface oxidation mechanisms on noble metal electrodes and may provide insights that might be important for future studies on interfacial electrochemistry and electrocatalysis.