On the behaviour of structure-sensitive reactions on single atom and dilute alloy surfaces

Papanikolaou, Konstantinos G.; Stamatakis, Michail

doi:10.1039/d0cy00904k

Cited by 10 publications

(8 citation statements)

References 74 publications

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“…This observed shift of ε d is the result of the d density of states (DOS) for dimers and trimers being closer to the Fermi level compared to Pd single atoms ( Fig. 1h), thereby explaining not only the strong Pd cluster-adsorbate interactions, but also why the cluster samples have higher reactivity than the SAA, albeit at the cost of selectivity 17,50,51 . In situ IR of Pd clustering and redispersion induced by CO.…”

Section: Resultsmentioning

confidence: 92%

Directing reaction pathways via in situ control of active site geometries in PdAu single-atom alloy catalysts

et al. 2021

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The atomic scale structure of the active sites in heterogeneous catalysts is central to their reactivity and selectivity. Therefore, understanding active site stability and evolution under different reaction conditions is key to the design of efficient and robust catalysts. Herein we describe theoretical calculations which predict that carbon monoxide can be used to stabilize different active site geometries in bimetallic alloys and then demonstrate experimentally that the same PdAu bimetallic catalyst can be transitioned between a single-atom alloy and a Pd cluster phase. Each state of the catalyst exhibits distinct selectivity for the dehydrogenation of ethanol reaction with the single-atom alloy phase exhibiting high selectivity to acetaldehyde and hydrogen versus a range of products from Pd clusters. First-principles based Monte Carlo calculations explain the origin of this active site ensemble size tuning effect, and this work serves as a demonstration of what should be a general phenomenon that enables in situ control over catalyst selectivity.

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Section: Resultsmentioning

confidence: 92%

Directing reaction pathways via in situ control of active site geometries in PdAu single-atom alloy catalysts

et al. 2021

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“…5. Interestingly, using the optB86b-vdW functional, Papanikolaou and Stamatakis 56 have calculated a similar energy (−0.74 eV) for the surface adsorbed oxygen atom binding atop the Ni single atom on the NiCu SAA catalyst. Due to the presence of Ni single atoms on the Cu surface, the O-H activation energy (route 1) is significantly reduced from 1.27 eV on Cu to 1.03 eV on the NiCu SAA surface.…”

Section: Resultsmentioning

confidence: 93%

Tracing the reactivity of single atom alloys for ethanol dehydrogenation using ab initio simulations

et al. 2022

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“…This small degree of structure sensitivity can be attributed to slight differences in the electronic state of the Rh atom, which arise from the different coordination environments of Rh in the two surfaces. 32 However, direct experimental evidence for SAA structure sensitivity on well-defined facets remains very limited. The first step toward elucidating the aforementioned effects involves the construction of SAA model catalysts on more open surfaces, and the key to that is a thorough understanding of alloy mechanisms of dopant atoms on these surface facets.…”

Section: Introductionmentioning

confidence: 99%

Surface facet dependence of competing alloying mechanisms

Wang

Papanikolaou

Hannagan

et al. 2020

The Journal of Chemical Physics

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Metal alloys are ubiquitous in many branches of heterogeneous catalysis, and it is now fairly well established that the local atomic structure of an alloy can have a profound influence on its chemical reactivity. While these effects can be difficult to probe in nanoparticle catalysts, model studies using well defined single crystal surfaces alloyed with dopants enable these structure-function correlations to be drawn. The first step in this approach involves understanding the alloying mechanism and the type of ensembles formed. In this study, we examined the atomic structure of RhCu single-atom alloys formed on Cu(111), Cu(100), and Cu(110) surfaces. Our results show a striking difference between Rh atoms alloying in Cu(111) vs the more open Cu(100) and Cu(110) surface facets. Unlike Cu(111) on which Rh atoms preferentially place-exchange with Cu atoms in the local regions above step edges leaving the majority of the Cu surface free of Rh, highly dispersed, homogeneous alloys are formed on the Cu(100) and ( 110) surfaces. These dramatically different alloying mechanisms are understood by quantifying the energetic barriers for atomic hopping, exchange, swapping, and vacancy filling events for Rh atoms on different Cu surfaces through theoretical calculations. Density functional theory results indicate that the observed differences in the alloying mechanism can be attributed to a faster hopping rate, relatively high atomic exchange barriers, and stronger binding of Rh atoms in the vicinity of step edges on Cu(111) compared to Cu(110) and Cu(100). These model systems will serve as useful platforms for examining structure sensitive chemistry on single-atom alloys.

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On the behaviour of structure-sensitive reactions on single atom and dilute alloy surfaces

Abstract: Typically structure sensitive dissociation reactions exhibit reduced structure-sensitivity when taking place over low-index single atom alloy surfaces.

Cited by 10 publications

References 74 publications

Directing reaction pathways via in situ control of active site geometries in PdAu single-atom alloy catalysts

Directing reaction pathways via in situ control of active site geometries in PdAu single-atom alloy catalysts

Tracing the reactivity of single atom alloys for ethanol dehydrogenation using ab initio simulations

Surface facet dependence of competing alloying mechanisms

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