STM investigation of oxygen dissociation on Ag/Cu(111) near surface alloy

Both experiment and theory have demonstrated the ability of near surface alloys (NSAs) to desirably tune catalyst properties. These alloys consist of a solute metal confined to the first few atomic layers and present in lower concentrations than the host metal. This alters the electronic and thus catalytic properties of the alloy. Deposition of Ag on Cu(111) leads to a well-characterized NSA with Ag confined to the uppermost layer. The presence of Ag in the topmost layer forms a dislocation loop in the underlying Cu(111) due to strain from lattice mismatch. Ag-based catalysts are the current industrial standard for many partial oxidation reactions, guiding our interest in oxidation dissociation on Ag/Cu(111). Herein, we report on the observation of oxygen dissociation on extended Ag ensembles on Cu(111) via room-temperature scanning tunneling microscopy (STM). Atomic oxygen coverage was observed to scale with increasing oxygen exposure. Through time-lapse STM images, we observed localized diffusion of oxygen on Ag ensembles. These results hint at the potential for this surface to perform partial oxidation reactions with enhanced selectivity and activity.