Is the methanation reaction over Ru single crystals structure dependent?

Abstract

The influence of monoatomic steps and defects on the methanation reaction over ruthenium has been investigated. The experiments are performed on a Ru(0 1 54) ruthenium single crystal, which contains one monoatomic step atom for each 27 terrace atoms. The methanation activity is measured at one bar of hydrogen and CO in a high pressure cell, which enables simultaneous measurements of the local reactivity of the well defined single crystal surface and the global reactivity of the entire crystal and its auxiliary support. By adding sulfur we observe that the measured activity from the well defined stepped front-side of the crystal is poisoned faster than the entire crystal containing more defects. We also observe that additional sputtering of the well-defined front-side increases the reactivity measured on the surface. Based on this, we conclude that the methanation reaction takes place on undercoordinated sites, such as steps and kinks, and that the methanation reaction is extremely structure dependent. Simulations of the flow, temperature, and product distributions in the high pressure cell are furthermore presented as supplementary information.

Selective CO Methanation on Highly Active Ru/TiO2 Catalysts: Identifying the Physical Origin of the Observed Activation/Deactivation and Loss in Selectivity

“…60 Similar conclusions were derived also for reaction on Ru single crystal surfaces. 61 The apparent discrepancy with the present observations may be related to the very small particle sizes in the present study, where other particle size related effects, such as size dependent changes in the electronic properties, may also play a role. Alternatively, this may also be related to metal support interactions, which had been demonstrated for Ru on the reducible TiO 2 support, 11 while it should be absent for Ru/SiO 2 or Ru single crystal surfaces.…”

Reflections on the Fischer-Tropsch synthesis: Mechanistic issues from a surface science perspective

“…the methanation reaction). Work by Chorkendorff and co workers showed that the activity of mass-selected supported ruthenium clusters for methanation correlates with the concentration of active sites such as step sites on the Ru surface [36,37]. Finally, the work of Quek et al [38] shows that the ability to dissociate CO is not restricted to step edges of a particular type.…”

Exploring the phase space of time of flight mass selected PtxY nanoparticles

“…The relevance of surface steps and defects for catalytic purposes has been elucidated by the work of Vendelbo et al, 20,21 who investigated the reactivity of the Ru(0154) surface (Ru(0001) with 4% steps) for methanation. Not only the steps proved to be of paramount importance for successful methane formation, but defects induced by sputtering readily improved the catalytic activity.…”