title: The origin of the selectivity and activity of ruthenium-cluster catalysts for fuel-cell feed-gas purification: a gas-phase approach.
abstract: Gas-phase ruthenium clusters Ru(n)(+) (n=2-6) are employed as model systems to discover the origin of the outstanding performance of supported sub-nanometer ruthenium particles in the catalytic CO methanation reaction with relevance to the hydrogen feed-gas purification for advanced fuel-cell applications. Using ion-trap mass spectrometry in conjunction with first-principles density functional theory calculations three fundamental properties of these clusters are identified which determine the selectivity and catalytic activity: high reactivity toward CO in contrast to inertness in the reaction with CO2; promotion of cooperatively enhanced H2 coadsorption and dissociation on pre-formed ruthenium carbonyl clusters, that is, no CO poisoning occurs; and the presence of Ru-atom sites with a low number of metal-metal bonds, which are particularly active for H2 coadsorption and activation. Furthermore, comprehensive theoretical investigations provide mechanistic insight into the CO methanation reaction and discover a reaction route involving the formation of a formyl-type intermediate.
authors.affiliation: Institute of Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm (Germany).
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Lang
authors.forename: Thorsten M
authors.initials: TM
authors.lastname: Bernhardt
authors.forename: Marjan
authors.initials: M
authors.lastname: Krstić
authors.forename: Vlasta
authors.initials: V
authors.lastname: Bonačić-Koutecký
keywords: CO methanation; ab initio calculations; heterogeneous catalysis; mass spectrometry; ruthenium clusters