Dynamics of Adatom and Vacancy Islands on Au(111) in Alkaline and Acidic Media

Gold (Au), especially single-crystalline Au(111), has been extensively studied in fundamental electrochemistry due to its unique properties, including high conductivity, chemical stability, and well-defined surface characteristics, which make it an ideal model system for electrochemical investigations. At the same time, the Au(111) surface is known to degrade during oxidation-reduction cycling in commonly used electrolytes, exhibiting the formation of atomic-scale vacancy and adatom islands. Although there are many fundamental studies on these degradation processes, only a limited number of studies have been performed in alkaline media. In this work, we study the roughening and healing characteristics of Au(111) upon oxidation-reduction treatments in H₂SO₄ and NaOH. We demonstrate that the surfaces are less rough after treatments in NaOH due to rapid smoothening over time. These observations point toward a higher driving force for island decay and to a higher surface mobility in NaOH, which substantially accelerates the surface healing process.