Redox-mediated C-C bond scission in alcohols adsorbed on CeO 2 - x thin films.

The decomposition mechanisms of ethanol and ethylene glycol on well-ordered stoichiometric CeO 2 (111) and partially reduced CeO 2- x (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 2 (111) involves formation of acetaldehyde-like intermediates and yields CO and CO 2 accompanied by desorption of acetaldehyde, H 2 O, and H 2 . This decomposition pathway leads to the formation of oxygen vacancies. In the presence of oxygen vacancies, C-O bond scission in ethoxy species yields C 2 H 4 . In contrast, C-C bond scission in ethylenedioxy species on the partially reduced CeO 2- x (111) is favored with respect to C-O bond scission and yields methanol, formaldehyde, and CO accompanied by the desorption of H 2 O and H 2 . Still, scission of C-O bonds on both sides of the ethylenedioxy species yields minor amounts of accompanying C 2 H 4 and C 2 H 2 . C-O bond scission is coupled with a partial recovery of the lattice oxygen in competition with its removal in the form of water.