Underpotential Deposition of Copper on Iodine-Modified Pt(111):  In Situ STM and ex Situ LEED Studies

The dynamic process of underpotential deposition (UPD) of copper on iodine-modified Pt(111) electrode in sulfuric acid solution was investigated by in situ scanning tunneling microscopy and ex situ low-energy electron diffraction. Prior to the copper deposition, iodine adlayer structures were characterized by both techniques. It was found that well-ordered iodine adlayers with the structures of (3 × 3) and ( × )R19.1° could be prepared by immersion of the electrode in a solution containing iodide ions under potential control. It was also found that the interconversion of the two structures was very slow. After the UPD of copper on the iodine-modified Pt electrode, the iodine atoms formed a c(p × R-30°) structure with a p value of ca. 2.6 on the (1 × 1) copper adlayer on Pt(111). After the copper was stripped, the electrode exhibited a mixture of (3 × 3) and ( × )R19.1° structures of iodine on Pt(111).