Efficient and selective carbon–carbon coupling on coke-resistant PdAu single-atom alloys

Réocreux, Romain; Uhlman, Matthew B.; Thuening, Theodore; Kress, Paul L.; Hannagan, Ryan T.; Stamatakis, Michail; Sykes, E. Charles H.

doi:10.1039/c9cc07932g

Cited by 23 publications

(53 citation statements)

References 26 publications

(27 reference statements)

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“…269 Such geometric effects have been employed in many other bimetallic systems to enhance the coke resistance and as such warrant further investigation in reactor studies. [277][278][279][280][281][282]…”

Section: Other Effectsmentioning

confidence: 99%

Guidelines to Achieving High Selectivity for the Hydrogenation of α,β-Unsaturated Aldehydes with Bimetallic and Dilute Alloy Catalysts: A Review

et al. 2020

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Selective hydrogenation of α,ß-unsaturated aldehydes to unsaturated alcohols is a challenging class of reactions, yielding valuable intermediates for the production of pharmaceuticals, perfumes, and flavorings. On monometallic heterogeneous catalysts, the formation of the unsaturated alcohols is thermodynamically disfavored over the saturated aldehydes. Hence, new catalysts are required to achieve the desired selectivity. Herein, the literature of three major research areas in catalysis is integrated as a step toward establishing the guidelines for enhancing the selectivity: reactor studies of complex catalyst materials at operating temperature and pressure; surface science studies of crystalline surfaces in ultrahigh vacuum; and first-principles modeling using density functional theory calculations. Aggregate analysis shows that bimetallic and dilute alloy catalysts significantly enhance the selectivity to the unsaturated alcohols compared to monometallic catalysts. This comprehensive review focuses primarily on the role of different metal surfaces as well as the factors that promote the adsorption of the unsaturated aldehyde via its C=O bond, most notably by electronic modification of the surface and formation of the electrophilic sites. Furthermore, challenges, gaps, and opportunities are identified to advance the rational design of efficient catalysts for this class of reactions, including the need for systematic studies of catalytic processes, theoretical modeling of complex materials, and model studies under ambient pressure and temperature.

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Section: Other Effectsmentioning

confidence: 99%

Guidelines to Achieving High Selectivity for the Hydrogenation of α,β-Unsaturated Aldehydes with Bimetallic and Dilute Alloy Catalysts: A Review

et al. 2020

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“…In catalysis, bimetallic nanosystems are often superior by their properties to the monometallic counterparts. For instance, there is a growing interest in a special class of bimetallic nanosystems, where a catalytically highly active metal, e.g., Pd or Pt, is distributed on the surface at sufficiently low concentration in the form of individual atoms embedded in the environment of a relatively inert metal, such as Au, Ag, or Cu [ 2 , 3 , 4 , 5 , 6 , 7 ]. These combinations allow solving a well-known problem whereby excellent reactivity of active metals often causes poor selectivity.…”

Section: Introductionmentioning

confidence: 99%

Pd Single-Atom Sites on the Surface of PdAu Nanoparticles: A DFT-Based Topological Search for Suitable Compositions

et al. 2021

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Structure of model bimetallic PdAu nanoparticles is analyzed aiming to find Pd:Au ratios optimal for existence of Pd1 single-atom surface sites inside outer Au atomic shell. The analysis is performed using density-functional theory (DFT) calculations and topological approach based on DFT-parameterized topological energy expression. The number of the surface Pd1 sites in the absence of adsorbates is calculated as a function of Pd concentration inside the particles. At low Pd contents none of the Pd atoms emerge on the surface in the lowest-energy chemical orderings. However, surface Pd1 sites become stable, when Pd content inside a Pd-Au particle reaches ca. 60%. Further Pd content increase up to almost pure Pd core is accompanied by increased concentration of surface Pd atoms, mostly as Pd1 sites, although larger Pd ensembles as dimers and linear trimers are formed as well. Analysis of the chemical orderings inside PdAu nanoparticles at different Pd contents revealed that enrichment of the subsurface shell by Pd with predominant occupation of its edge positions precedes emergence of Pd surface species.

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“…We showed in our previous work on PdAu SAAs that, while the (111) surface provides a good model for Au sites, the (211) surface is necessary to describe the reactivity of Pd sites. 5 Similarly, we consider here that the Ni sites in the NiAu SAA are located at the (211) facet and that the Au sites are well described by the (111) surface. As with the PdAu SAA, the overall activation energy for the C-C coupling of methyl groups depends on the initial coverage and the associated representative initial state (see Figure 3 and 4a-c).…”

Section: Resultsmentioning

confidence: 99%

“…4 Specific to this work, PdAu single-atom alloys (SAAs) investigated using a model single crystal approach, have been shown to perform selective sp 3 -sp 3 carbon-carbon coupling when methyl iodide is used as the reactant. 5 While Pd is a commonly used metal for coupling reactions, Ni is an attractive alternative of interest, in part, due to its lower cost.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic insights into carbon–carbon coupling on NiAu and PdAu single-atom alloys

Kress

Réocreux

Hannagan

et al. 2021

The Journal of Chemical Physics

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Carbon-carbon coupling is an important step in many catalytic reactions and performing sp 3 -sp 3 carbon-carbon coupling heterogeneously is particularly challenging. It has been reported that PdAu single-atom alloy (SAA) model catalytic surfaces are able to selectively couple methyl groups producing ethane from methyl iodide. Herein, we extend this study to NiAu SAAs and find that Ni atoms in Au are active for C-I cleavage and selective sp 3 -sp 3 carbon-carbon coupling to produce ethane. Furthermore, we performed ab initio kinetic Monte Carlo simulations that include the effect of the iodine atom, which was previously considered a bystander species. We find that model NiAu surfaces exhibit a similar chemistry to PdAu, but the reason for the similarity is due to the role the iodine atoms play in terms of blocking the Ni atom active sites. Specifically, on NiAu SAAs the iodine atoms outcompete the methyl groups for occupancy of the Ni sites leaving the Me groups on Au, while on PdAu SAAs, the binding strengths of methyl groups and iodine atoms at the Pd atom active site are more similar. These simulations shed light on the mechanism of this important sp 3 -sp 3 carbon-carbon coupling chemistry on SAAs. Furthermore, we discuss the effect of the iodine atoms on the reaction energetics and make an analogy between the effect of iodine as an active site blocker on this model heterogeneous catalyst and homogeneous catalysts in which ligands must detach in order for the active site to be accessed by the reactants.

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Efficient and selective carbon–carbon coupling on coke-resistant PdAu single-atom alloys

Abstract: We demonstrate that PdAu single-atom alloy model catalysts offer a heterogeneous route to selective Würtz-type C–C coupling.

Cited by 23 publications

References 26 publications

Guidelines to Achieving High Selectivity for the Hydrogenation of α,β-Unsaturated Aldehydes with Bimetallic and Dilute Alloy Catalysts: A Review

Guidelines to Achieving High Selectivity for the Hydrogenation of α,β-Unsaturated Aldehydes with Bimetallic and Dilute Alloy Catalysts: A Review

Pd Single-Atom Sites on the Surface of PdAu Nanoparticles: A DFT-Based Topological Search for Suitable Compositions

Mechanistic insights into carbon–carbon coupling on NiAu and PdAu single-atom alloys

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