Dehydrogenation of ethanol on an O2-4Rh/CeO2-x(1 1 1) surface: A computational study

We applied the periodic density-functional theory to investigate the dehydrogenation of ethanol on the O2-4Rh/CeO2-x(1 1 1) surface with an assumption that one defect site of that CeO2 surface creates an O vacancy that an excess O2 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 β-carbon hydrogen of ethanol are eliminated. The dehydrogenation continues with the loss of two hydrogens from the α-carbon, at the same time, transforming to a four-membered ring species (Rh-CH2C(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 CH2. The ensuing steam-reforming process (CH2 + H2O) and the mechanism of the consecutive dehydrogenation are also discussed.