The mechanism of olefin hydrogenation on a supported noble‐metal catalyst requires the presence of weakly bound hydrogen atoms absorbed in the volume of the metal particle (see picture). Co‐adsorbed carbonaceous deposits affect the hydrogen distribution in the metal clusters and critically control their activity and selectivity in olefin conversions.
Ceria (CeO) has recently been found to be a promising catalyst in the selective hydrogenation of alkynes to alkenes. This reaction occurs primarily on highly dispersed metal catalysts, but rarely on oxide surfaces. The origin of the outstanding activity and selectivity observed on CeO remains unclear. In this work, we show that one key aspect of the hydrogenation reaction-the interaction of hydrogen with the oxide-depends strongly on the presence of O vacancies within CeO. Through infrared reflection absorption spectroscopy on well-ordered CeO(111) thin films and density functional theory (DFT) calculations, we show that the preferred heterolytic dissociation of molecular hydrogen on CeO(111) requires H pressures in the mbar regime. Hydrogen depth profiling with nuclear reaction analysis indicates that H species stay on the surface of stoichiometric CeO(111) films, whereas H incorporates as a volatile species into the volume of partially reduced CeO(111) thin films (x ∼ 1.8-1.9). Complementary DFT calculations demonstrate that oxygen vacancies facilitate H incorporation below the surface and that they are the key to the stabilization of hydridic H species in the volume of reduced ceria.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.