Abstract
The present manuscript describes the preparation, surface characterization, and interfacial electrochemistry of ultrathin Pd films, from submonolayer to multilayer coverages, electrodeposited on well-defined Pt(111) surfaces. Between the coverage regimes studied, the growth of the films followed the Stranski-Krastanov mechanism. The interfacial electrochemical properties associated with the film-to-bulk transition were characterized by voltammetric techniques in combination with low-energy electron diffraction and Auger electron spectroscopy. It was found that the Pd electrodeposit started to exhibit bulk-like properties at three monolayers. Voltammetric cycling, between the hydrogen evolution and the double-layer regions, was found to exert minimal influence on the smoothening of the electrodeposited films. However, cycling within the same potential region in the presence of bromide anions (at which Br- adsorption/Br desorption takes place) considerably smoothened the initially rough Pd films, comparable to hightemperature annealing. The influence of chemisorbed bromine on the anodic dissolution of Pd was also studied. The present studies indicated that bromine was desorbed along with the dissolution of the Pd step-atoms in a manner that may be described as electrochemical digital etching.
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