We applied the periodic density-functional theory to investigate the dehydrogenation of ethanol on the O(2)-4Rh/CeO(2-x)(111) surface with an assumption that one defect site of that CeO(2) surface creates an O vacancy that an excess O(2) molecule replaces. Under these conditions, the adsorption energy of ethanol is calculated to be -16.08 kcal/mol. Before formation of a five-membered ring of an oxametallacyclic compound, the hydrogen atom of O-H and that of one beta-carbon hydrogen of ethanol are eliminated. The dehydrogenation continues with the loss of two hydrogens from the alpha-carbon, at the same time, transforming to a four-membered ring species (Rh-CH(2)C(O)-Rh). Scission of the C-C bond occurs at this stage with a dissociation barrier 14.38 kcal/mol, forming adsorbed products CO and CH(2). The ensuing steam-reforming process (CH(2) + H(2)O) and the mechanism of the consecutive dehydrogenation are also discussed. (C) 2009 Elsevier B.V. All rights reserved.
