Methanol decomposition on low index and stepped CeO2 surfaces from GGA plus U

GGA + U calculations have been carried out to study the complete methanol decomposition on the more stable Ceria surfaces, i.e. (111), (221), (331) and (110). These results have shown that the methanol adsorption is exothermic on oxidized as well as on the partially reduced surfaces though the adsorption energy is greater for the latest. The first dehydrogenation step of methanol is highly probable for all the studied sites with activation barriers smaller than 0.2 eV. The first dehydrogenation reaction could also occur by breaking the C-H methyl bond, but we found that this reaction is very unlikely. Reaction and activation energies for the second dehydrogenation - from methoxy to formaldehyde, are very similar for perfect (111) and stepped surfaces but these activation barriers are not negligible, almost ten times as many the first step barriers. Next, the formaldehyde decomposition to formyl and CO species on perfect CeO2(111) have an important energetic cost, therefore these reactions could occur only on stepped surfaces. (C) 2016 Elsevier B.V. All rights reserved.