Electrodeposition of Copper on Platinum (111) Surfaces Pretreated with Iodine: Studies by LEED, Auger Spectroscopy, and Electrochemistry

Abstract

Studies by low energy electron diffraction (LEED) and Auger spectroscopy of copper electrodeposited on well‐characterized platinum (111) surfaces from aqueous sodium perchlorate solutions are reported. Prior to electrodeposition, the platinum (111) surface was pretreated with vapor in ultrahigh vacuum to form a Pt(111) R19.1°‐I superlattice, which protected the platinum surface and the surface of the electrodeposit from attack by the electrolyte and contamination by residual gases. The results were as follows: electrodeposition took place in two narrow, overlapping underpotential deposition linear scan voltammetric peaks followed by one conventional bulk copper deposition peak. Underpotential deposition produced an ordered layer. The first underpotential deposition peak formed a superlattice in which the unit cell contained four iodine atoms and a comparable number of Cu atoms per nine surface Pt atoms . At completion of the underpotential deposition process a coincidence lattice was present in which and . The iodine Auger signal was not appreciably affected by Cu deposition, indicating that the iodine atoms were present in the topmost layer of the surface at all Cu coverages.