Ethylene Glycol Adsorption and Reaction over CeOx(111) Thin Films

This study reports the interaction of ethylene glycol with well-ordered CeOx(111) thin film surfaces. Ethylene glycol initially adsorbs on fully oxidized CeO2(111) and reduced CeO2-x(111) through the formation of one C-O-Ce bond and then forms a second alkoxy bond after annealing. On fully oxidized CeO2(111) both recombination of ethylene glycol and water desorption occur at low temperature leaving stable -OCH2CH2O- (ethylenedioxy) intermediates and oxygen vacancies on the surface. This ethylenedioxy intermediate goes through C-C bond scission to produce formate species which then react to produce CO and CO2. The formation of water results in the reduction of the ceria. On a reduced CeO2-x(111) surface the reaction selectivity shifts toward a dehydration process. The ethylenedioxy intermediate decomposes by breaking a C-O bond and converts into an enolate species. Similar to the reaction of acetaldehyde on reduced CeO2-x(111), the enolate reacts to produce acetaldehyde, acetylene, and ethylene. The loss of 0 from ethylene glycol leads to a small amount of oxidation of the reduced ceria.