Abstract
An isothermal desorption spectroscopy study of carbon monoxide adsorbed on clean, vapor deposited, epitaxial (111) Pd films grown on mica was carried out using Auger electron spectroscopy (AES) techniques. Saturation CO coverages were obtained at room temperature and followed by AES peak‐to‐peak height measurements as a function of time at elevated temperatures ranging from 90 to 130 °C. Data analysis was carried out using first‐order kinetics that yielded an activation energy for desorption Ed =24.0±0.3 kcal/mol. This value was found to apply to surface coverages ranging from saturation down to a few percent of saturation at the higher temperatures used. Previous studies by others on (111) Pd surfaces using flash desorption and contact potential methods have shown that at low coverage the desorption energy is ∼34 kcal/mol; but that as saturation coverage is approached, the desorption energy drops sharply to 22–24 kcal/mol. The present isothermal annealing results on epitaxial thin films are thus in agreement with previous near saturation coverage results using different methods. However, the present work indicates a constant desorption energy as the coverage decreases to values that are small fractions of saturation.
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