CO induced surface segregation as a means of improving surface composition and enhancing performance of CuPd bimetallic catalysts

McCue, Alan J.; Anderson, James A.

doi:10.1016/j.jcat.2015.06.002

Cited by 85 publications

(86 citation statements)

References 64 publications

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“…CO). 27,28,32,34 Indeed, adsorbates that interact strongly with metal atoms usually enrich the surface of bimetallic catalysts with those metal atoms. 68 Thus, we continue by considering the possibility of inducing segregation through CO adsorption.…”

Section: Surface Segregation Studiesmentioning

confidence: 99%

“…CO, H2, NO and O2) in the aim of improving the catalytic properties of the material. 6,28,[31][32][33][34] CO is typically used as a probe molecule for specifying the properties of adsorption on solid materials 32,35 and it is known for inducing morphological changes to the catalytic surface when adsorbed thereon. For example, highly mobile carbonyl species on Pt-and Pd-doped Fe3O4(001) are observed with scanning tunnelling microscopy (STM) after exposure of the surfaces to CO gas at low PCO (e.g.…”

Section: Introductionmentioning

confidence: 99%

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CO-Induced Aggregation and Segregation of Highly Dilute Alloys: A Density Functional Theory Study

2019

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Highly dilute binary alloys composed of an active platinum group metal (PGM) and a more inert coinage metal are important in the field of catalysis, as they function as active and selective catalysts. Their catalytic properties depend on the surface "ensemble" of PGM atoms, whose size may be altered under reactive conditions. We use density functional theory and investigate the interaction of CO, a molecule common in numerous industrially important chemistries, with alloys that are composed of a PGM (Pt, Pd, Rh, Ir, Ni) doped in coinage metal hosts (Cu, Au, Ag). We study the adsorption of CO on the (211) step and (100) facet and compare our results to those previously obtained on the (111) facet. We determine strong correlations between the adsorption energies of CO across the facets and highlight the corresponding thermochemical scaling relations. Finally, we study the stability of isolated surface dopant atoms with respect to aggregation into clusters and segregation into the bulk, both in the presence and absence of CO. We find that strong COdopant interactions significantly influence the morphology of the catalyst surface, suggesting that it may be possible to establish control over the ensemble size of the dopant by tuning PCO.

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Section: Surface Segregation Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

CO-Induced Aggregation and Segregation of Highly Dilute Alloys: A Density Functional Theory Study

2019

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“…Additionally, we recognize that the presence of adsorbates may induce structural changes in binary alloy materials, such as segregation of atoms from the bulk into the surface layer, as well as promoting aggregation and island formation [26][27][28][29][30][31][32][33][34]. Such changes are caused by differences in adsorption behaviour between an adsorbate on each metallic component of the alloy; these differences can offset or increase the energy change upon restructuring of the material.…”

Section: Introductionmentioning

confidence: 99%

Carbon Monoxide Poisoning Resistance and Structural Stability of Single Atom Alloys

et al. 2018

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Platinum group metals (PGMs) serve as highly active catalysts in a variety of heterogeneous chemical processes. Unfortunately, their high activity is accompanied by a high affinity for CO and thus, PGMs are susceptible to poisoning. Alloying PGMs with metals exhibiting lower affinity to CO could be an effective strategy toward preventing such poisoning. In this work, we use density functional theory to demonstrate this strategy, focusing on highly dilute alloys of PGMs (Pd, Pt, Rh, Ir and Ni) with poison resistant coinage metal hosts (Cu, Ag, Au), such that individual PGM atoms are dispersed at the atomic limit forming single atom alloys (SAAs). We show that compared to the pure metals, CO exhibits lower binding strength on the majority of SAAs studied, and we use kinetic Monte Carlo simulation to obtain relevant temperature programed desorption spectra, which are found to be in good agreement with experiments. Additionally, we consider the effects of CO adsorption on the structure of SAAs. We calculate segregation energies which are indicative of the stability of dopant atoms in the bulk compared to the surface layer, as well as aggregation energies to determine the stability of isolated surface dopant atoms compared to dimer and trimer configurations. Our calculations reveal that CO adsorption induces dopant atom segregation into the surface layer for all SAAs considered here, whereas aggregation and island formation may be promoted or inhibited depending on alloy constitution and CO coverage. This observation suggests the possibility of controlling ensemble effects in novel catalyst architectures through CO-induced aggregation and kinetic trapping.

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“…Informed by surface chemistry and microscopy studies, a number of different research groups have developed a new generation of PdCu, PdAu, PdAg, RhAu and PtCu SAA nanoparticle catalysts for the selective hydrogenation of acetylene, phenylacetylene, styrene, hexyne and butadiene under realistic reaction conditions as well as Ullmann coupling. 50,[54][55][56][57][58][59][60][61][62][63][64] At low loadings, in situ extended X-ray absorption fine structure and aberration-corrected high angle annular dark field scanning transmission electron microscopy were used to show that Pt exists as individual, isolated atoms substituted into the Cu NP surface both before and after reaction. Nominal amounts of Pt (2 at.…”

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confidence: 99%

Lonely Atoms with Special Gifts: Breaking Linear Scaling Relationships in Heterogeneous Catalysis with Single-Atom Alloys

Darby

Stamatakis

Michaelides

et al. 2018

J. Phys. Chem. Lett.

252

274

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We discuss a simple yet effective strategy for escaping traditional linear scaling relations in heterogeneous catalysis with highly dilute bimetallic alloys known as single-atom alloys (SAAs). These systems, in which a reactive metal is atomically dispersed in a less reactive host, were first demonstrated with the techniques of surface science to be active and selective for hydrogenation reactions. Informed by these early results, PdCu and PtCu SAA nanoparticle hydrogenation catalysts were shown to work under industrially relevant conditions. To efficiently survey the many potential metal combinations and reactions, simulation is crucial for making predictions about reactivity and guiding experimental focus on the most promising candidate materials. This recent work reveals that the high surface chemical heterogeneity of SAAs can result in significant deviations from Brønsted-Evans-Polanyi scaling relationships for many key reaction steps. These recent insights into SAAs and their ability to break linear scaling relations motivate discovery of novel alloy catalysts.

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CO induced surface segregation as a means of improving surface composition and enhancing performance of CuPd bimetallic catalysts

Cited by 85 publications

References 64 publications

CO-Induced Aggregation and Segregation of Highly Dilute Alloys: A Density Functional Theory Study

CO-Induced Aggregation and Segregation of Highly Dilute Alloys: A Density Functional Theory Study

Carbon Monoxide Poisoning Resistance and Structural Stability of Single Atom Alloys

Lonely Atoms with Special Gifts: Breaking Linear Scaling Relationships in Heterogeneous Catalysis with Single-Atom Alloys

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