A STUDY OF THE PD HIGHLY ORIENTED PYROLYTIC-GRAPHITE ELECTRODEPOSITION SYSTEM BY IN-SITU ELECTROCHEMICAL SCANNING-TUNNELING-MICROSCOPY

Palladium electrodeposition has significant industrial application in the plating of electrical contacts and academic importance in studies of hydrogen permeation in metals. We used a simple palladous chloride electrolyte and a highly ordered pyrolytic graphite substrate to study the early stages of Pd electrodeposition in situ by means of potentiodynamics and scanning tunnelling microscopy, also by conventional electrochemical measurements and scanning electron microscopy. The initial nucleation and growth of Pd crystallites occurred predominantly at surface defects; alterations in the electrodeposition conditions were found to affect the size, distribution and morphology of the Pd deposit. For the in situ scanning tunnelling microscopy experiments, a tip field-induced modification of the local electrochemical behaviour at the surface was observed that restricted Pd nucleation and growth within a region of substrate underneath the tip.