High-resolution x-ray photoelectron spectroscopy study of the ethanol oxidation reaction on Pd(110)

The adsorption, decomposition, and oxidation of ethanol on Pd(110) has been studied using high-resolution x-ray photoelectron spectroscopy (XPS) and temperature-programmed XPS. The decomposition pathways of ethanol on the clean surface (to methane, hydrogen and carbon monoxide; and to methane, hydrogen, and carbon and oxygen adatoms) previously studied using molecular beam and thermal desorption spectroscopy were confirmed by this study. The presence of an overlayer of oxygen did not significantly alter the major or minor decomposition pathways observed on the clean surface, except for the production of water and, at temperatures above 380 K, carbon dioxide as oxidation products. It also resulted in the formation of acetate, which was first seen during temperature-programmed desorption as coincident carbon dioxide and hydrogen desorption, and was confirmed by XPS. Two C 1s peaks, one assigned to the methyl carbon in acetate and the other to the carboxylate carbon, developed simultaneously during TPXPS. The disappearance of these peaks in XPS occurred at a similar temperature (400 K) to that seen during temperature-programmed desorption. (C) 1999 American Institute of Physics. [S0021-9606(99)70217-5].