AFM STUDY OF THE STRUCTURE OF UNDERPOTENTIALLY DEPOSITED AG AND HG ON AU(111)

The AFM was utilized to determine the structure of underpotentially deposited monolayers of Ag and Hg on Au(111) electrode surfaces. Monolayers of Ag exhibit different structures in different electrolytes. Specifically, in sulfate we find a 3 X 3 structure, in nitrate, a 4 X 4 structure, in perchlorate another open structure, and in acetate a close-packed 1 X 1 structure. The packing density of Ag in each system correlates with the size of the electrolyte, with larger anions yielding more open structures. Monolayers of Hg exhibit a hexagonal structure with a-0.58 nm atom-atom distance in sulfate, nitrate, and perchlorate electrolytes. The insensitivity of structure to electrolyte in this system may relate to the substantial partial charge remaining on the Hg. This study suggests that several factors are responsible for the observed monolayer structures.