Redox-mediated C-C bond scission in alcohols adsorbed on CeOthin films.

The decomposition mechanisms of ethanol and ethylene glycol on well-ordered stoichiometric CeO(111) and partially reduced CeO(111) films were investigated by means of synchrotron radiation photoelectron spectroscopy, resonant photoemission spectroscopy, and temperature programmed desorption. Both alcohols partially deprotonate upon adsorption at 150 K and subsequent annealing yielding stable ethoxy and ethylenedioxy species. The C-C bond scission in both ethoxy and ethylenedioxy species on stoichiometric CeO(111) involves formation of acetaldehyde-like intermediates and yields CO and COaccompanied by desorption of acetaldehyde, HO, and H. This decomposition pathway leads to the formation of oxygen vacancies. In the presence of oxygen vacancies, C-O bond scission in ethoxy species yields CH. In contrast, C-C bond scission in ethylenedioxy species on the partially reduced CeO(111) is favored with respect to C-O bond scission and yields methanol, formaldehyde, and CO accompanied by the desorption of HO and H. Still, scission of C-O bonds on both sides of the ethylenedioxy species yields minor amounts of accompanying CHand CH. C-O bond scission is coupled with a partial recovery of the lattice oxygen in competition with its removal in the form of water.