The reactions of acetone with the surfaces of uranium dioxide single crystal and thin film

Abstract

The reaction of acetone, as an example of a carbonyl compound, is studied over UO 2 (1 1 1) single crystal and thin film surfaces. Over the stoichiometric single crystal surface, acetone is molecularly and weakly adsorbed with a computed activation energy for desorption in the range of 95–65 kJ/mol with pre-exponential factors between 10 11 and 10 13 s −1. On the contrary, acetone reacts very strongly on the O-defected single crystal and thin film surfaces. In addition to total decomposition evidence of aldolization and cyclization reactions were seen. The thin film of UO 2 was studied by synchrotron light, providing high resolution photoelectron spectroscopy in the core level, and high sensitivity in the both the core and valence band regions. The U5f line was considerably enhanced at grazing angle when compared to that obtained at normal angle for the O-defected surface, showing that the surface is more reduced than the next layers. The U 4f lines indicated the presence of U cations in lower oxidation states than +4 for the O-defected surface. These lines were considerably attenuated upon adsorption of acetone, due to surface oxidation by C O bond dissociation. The reaction pathway for acetone on the O-defected surface is presented, and compared to that of the previously studied acetaldehyde molecule.