Detailed underpotential deposition of copper on gold(III) in aqueous solutions

Abstract

In situ electrochemical scanning tunneling microscopy (ESTM) is applied to a gold(111) surface with atomic resolution in aqueous sulfuric add solutions. Real-space images of close-packed Au atoms are stably resolved on an Au(111) facet in a “pure” H 2SO 4 solution. It is concluded that (3 1 2 × 3 1 2 )R30° is the structure for the first underpotential deposition of copper on Au(111). The (3 1 2 × 3 1 2 )R30° is the only observable structure for a long period of time in the entire potential range between 0.18 V and 0.1 V vs. a saturated calomel electrode. Two distinctly different phase boundaries are found between nearly perfect (3 1 2 × 3 1 2 )R30° domains. The initial stages of the UPD of Cu have been investigated carefully.