title: How absorbed hydrogen affects the catalytic activity of transition metals.
abstract: Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, H(sub) , may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, H(ad) , depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of H(sub) , especially on metal nanoparticles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general.
authors.affiliation: Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain) http://www.icrea.cat/Web/ScientificForm.aspx?key=292; Faculty of Chemistry and Pharmacy, University of Sofia, 1126 Sofia (Bulgaria).
authors.forename: Hristiyan A
authors.initials: HA
authors.lastname: Aleksandrov
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Kozlov
authors.forename: Swetlana
authors.initials: S
authors.lastname: Schauermann
authors.forename: Georgi N
authors.initials: GN
authors.lastname: Vayssilov
authors.forename: Konstantin M
authors.initials: KM
authors.lastname: Neyman
mesh_terms: D000327:Adsorption; D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry*; D006865:Hydrogenation; D053768:Metal Nanoparticles / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D008958:Models, Molecular; D013499:Surface Properties; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D008670:Metals; D028561:Transition Elements; D006859:Hydrogen
keywords: density functional calculations; heterogeneous catalysis; hydrogenations; nanoparticles; surface chemistry