Abstract
Methanol decomposition to formaldehyde catalyzed by the ceria (111) surface has been investigated using the DFT+U method. Our results rationalize experimental temperature programmed desorption experiments on the fully oxidized surface. Particular attention has been paid to the model correctness of methoxy with coadsorbed hydrogen on the surface. This issue has been raised by the experimental observation of water desorption at low temperature removing hydrogen from the system. Our investigation also includes hydrogen diffusion as a means of hydrogen removal. We show that the $\rm CH_3O^-/H^+$ ion pair remains at large separation, rendering the coadsorbed model as appropriate in contrast to a neutral isolated methoxy, for which the dehydrogenation barrier becomes negligible. We find that the presence of methoxy reduces the reaction energy for water formation considerably. In addition, the preference of the electron to locate at the methoxy oxygen results in a dehydrated surface that does not contain Ce3+ ions, despite the existence of a vacancy.