Theoretical calculation of the dehydrogenation of ethanol on a Rh/CeChO₂(111) surface

We applied periodic density-functional theory (DFT) to investigate the dehydrogenation of ethanol on a Rh/ CeO₂ (111) surface. Ethanol is calculated to have the greatest energy of adsorption when the oxygen atom of the molecule is adsorbed onto a Ce atom in the surface, relative to other surface atoms (Rh or O). Before forming a six-membered ring of an oxametallacyclic compound (Rh-CH₂CH₂O-Ce_(a)), two hydrogen atoms from ethanol are first eliminated; the barriers for dissociation of the O-H and the β-carbon (CH₂-H) hydrogens are calculated to be 12.00 and 28.57 kcal/mol, respectively. The dehydrogenated H atom has the greatest adsorption energy (E_ads = 101.59 kcal/mol) when it is adsorbed onto an oxygen atom of the surface. The dehydrogenation continues with the loss of two hydrogens from the α-carbon, forming an intermediate species Rh-CH₂CO-Ce_(a), for which the successive barriers are 34.26 and 40.84 kcal/mol. Scission of the C-C bond occurs at this stage with a dissociation barrier E_a = 49.54 kcal/mol, to form Rh-CH_2(a) + 4H_(a) + CO_(g). At high temperatures, these adsorbates desorb to yield the final products CH _4(g), H_2(g), and CO_(g).