Anomalous Dependence of the Reactivity on the Presence of Steps: Dissociation of D₂ on Cu(211)

Abstract

Stepped metal surfaces are usually assumed to exhibit an increased catalytic activity for bond cleavage of small molecules over their flat single-crystal counterparts. We present experimental and theoretical data on the dissociative adsorption of molecular hydrogen on copper that contradicts this notion. We observe hydrogen molecules to be more reactive on the flat Cu(111) than on the stepped Cu(211) surface. We suggest that this exceptional behavior is due to a geometric effect, that is, that bond cleavage on the flat surface does not occur preferentially over a top site.

Associative desorption of hydrogen isotopologues from copper surfaces: Characterization of two reaction mechanisms

“…[67][68][69][70][71][72] In this work, we observe systematically higher E 0 (v, J) values (by 30-130 meV) for the fast channel reaction on Cu(211) compared to Cu(111). This is consistent with a recent study by Füchsel et al, 52 who reported molecular beam adsorption measurements and complementary theoretical calculations, showing that the Cu(211) facet is less reactive than Cu(111).…”

“…There have been many studies on the dissociative adsorption of hydrogen on copper. 7,11,13,18,19,23,27,[34][35][36][37][39][40][41][43][44][45][47][48][49][50][51][52]61,65 E 0 (v, J) values from the most directly comparable studies 27,47,51 are shown in Fig. 11 systematically lower, despite the fact that the experimental approach was nominally identical to the present one.…”

“…This is consistent with recently published work showing the Cu(211) surface to be less reactive to H 2 than Cu(111). 52 The "slow channel" 51 has not been explained by theory, yet it occurs on both copper facets with a comparable yield to the "fast channel." We discuss possible mechanisms consistent with the observed dynamics of this still-unexplained reaction.…”

Test of the Transferability of the Specific Reaction Parameter Functional for H2 + Cu(111) to D2 + Ag(111)

“…In method 2, only dynamically relevant points in the barrier region were selected: 300 randomly selected points were taken from QCT calculations, from 10 4 trajectories, a further restriction being 0.7 Å ≤ r ≤ 2.3 Å and 0.9 Å ≤ Z ≤ 3.5 Å. (For more details, we refer the reader to ref ( 43 ).)…”

On‐the‐fly Catalyst Modification: Strategy to Improve Catalytic Processes Selectivity and Understanding

“…Hydrogenation reactions using molecular hydrogen include H 2 adsorption and dissociation. This step is infrequently rate controlling on transition metal surfaces where the dissociation is known to be facile and structure insensitive, with opposing observations often labelled as anomalous . However, the reaction of atomic H with hydrocarbon reactants has been measured to be structure sensitive.…”