In depth analysis of complex interfacial processes: in situ electrochemical characterization of deposition of atomic layers of Cu, Pb and Te on Pd electrodes

Abstract

A combination of cyclic voltammetry, electrogravimetry, and electrochemical impedance spectroscopy has been used to characterize, in situ, the underpotential deposition (UPD) of atomic layers of Cu, Pb and Te on Pd electrode surfaces. This approach provides co-adsorption and competitive adsorption of anions to be measured and quantified during the UPD processes, highlighting the complex competitive processes that can e.g. hinder the design of new catalysts. The formed Cu, Pb and Te atomic layers on the Pd electrode showed no evidence of anion co-adsorption or surface alloying effects, which indicates that these systems, when formed in a perchlorate medium, could act as building blocks for catalysts. The mode of deposition was found to vary greatly for each overlayer. Cu was found to form a compact monolayer on the Pd surface, while Te formed a bilayer structure on the Pd surface, of which ∼1/4 of a monolayer was found to be irreversibly adsorbed. The formation of Pb overlayers was complicated by background UPD of hydrogen and its absorption to the underlying Pd substrate. While perchloric acid media are suitable for the formation of the overlayer, catalytic application of the formed Pb-layers would require a higher pH to negate such processes.