ELECTRODEPOSITION OF COPPER ON PT(111) AND PT(100) SINGLE-CRYSTAL SURFACES

The electrodeposition of copper on Pt(100) and Pt(111) in different acid electrolytes was studied by cyclic voltammetry, ex situ Auger electron spectroscopy and low energy electron diffraction (LEED). The specific adsorption of Cl- from HF and HClO4 solutions was found to have a strong effect on the submonolayer deposition process. LEED results from emersed electrodes indicated that for submonolayer deposition from a ''chloride free'' solution the copper was growing in islands (or ''patches'') having the lattice constant of the platinum substrate, i.e., pseudomorphic growth as in vapor deposition of Cu on Pt. In the presence of Cl-submonolayers of Cu were deposited in the form of a Cu-Cl adlattice. After deposition at either the Nernst potential (one monolayer) or at approximately 0.2 V negative of it (four monolayers), Cu formed a uniform epitaxial metallic layer with an ordered Cl adlayer on the top of the Cu layer in a structure esssentially identical to that for Cl adsorbed from the gas phase onto a bulk Cu crystal to saturation.