Theoretical Calculation of the Dehydrogenation of Ethanol on a Rh/CeO₂(111) Surface

Abstract

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 beta-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 alpha-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 Ea = 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).

A Phenomenological Study of the Metal–Oxide Interface: The Role of Catalysis in Hydrogen Production from Renewable Resources

“…[3,13,14] The initiation of the reaction occurs because Rh can break the sp 3 CÀH terminal bond of hydrocarbons, with low activation energy as compared to all other 4d transition metals. [15,[16][17][18] Rh alone does not make a good catalyst owing to its relatively weak HÀH recombination activity. We show that the presence of a second metal such as Pd or Pt (both are efficient for HÀH bond formation) is necessary to maintain high catalytic activity.…”

Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

“…Second, Rh/SrTiO 3 produces large amounts of methane when compared to Pt/SrTiO 3 . The larger amounts of methane can be rationalized by the fact that Rh is more active in breaking the C-C bond compared to Pt [19][20][21]. In this case, the ratio H 2 to CH 4 is equal to 2 for Rh/SrTiO 3 while it is equal to 8 in the case of Pt/SrTiO 3 .…”

Catalytic Hydrogen Production from Bioethanol

“…The surface layer is thereafter allowed to be reconstructed in response to the constraint from bulk layers. Usually, a vacuum region with certain length is created right above the top layer of the slab model to prevent the interaction of adsorbed molecules with its periodic images [140]. The choice of supercell size comes from the compromise between computation accuracy and computation time span.…”