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

Ouyang, Mengyao; Papanikolaou, Konstantinos G.; Boubnov, Alexey; Hoffman, Adam S.; Giannakakis, Georgios; Bare, Simon R.; Stamatakis, Michail; Flytzani‐Stephanopoulos, Maria; Sykes, E. Charles H.

doi:10.1038/s41467-021-21555-z

Cited by 116 publications

(126 citation statements)

References 91 publications

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“…On larger Pd ensembles, just as on pure Pd, 27 recombination of chemisorbed H atoms to chemisorbed H 2 is rate limiting due to the stronger hydrogen-Pd ensemble bond compared to the hydrogen-single Pd atom bond. 12,14 Similarly, the binding energies of carbon mono-oxide 29,30 and oxygen 14 have been reported to increase with increasing Pd ensemble size for Au-Pd single crystal surfaces.…”

Section: Discussionmentioning

confidence: 94%

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

et al. 2021

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Dilute Pd-in-Au alloy catalysts are promising materials for selective hydrogenation catalysis. Extensive surface science studies have contributed mechanistic insight on the energetic aspect of hydrogen dissociation, migration and recombination on dilute alloy systems. Yet, translating these fundamental concepts to the kinetics and free energy of hydrogen dissociation on nanoparticle catalysts operating at ambient pressures and temperatures remains challenging. Here, the effect of the Pd concentration and Pd ensemble size on the catalytic activity, apparent activation energy and rate limiting process is addressed by combining experiment and theory. Experiments in a flow reactor show that a compositional change from 4 to 8 atm% Pd of the Pd-in-Au alloy catalyst leads to strong increase in activity, even exceeding the activity per Pd atom of monometallic Pd under the same conditions, albeit with an increase in apparent activation energy. First-principles calculations show that the rate and apparent activation enthalpy for HD exchange increase when increasing the Pd ensemble size from single Pd atoms to Pd trimers in a Au surface, suggesting that the ensemble size distribution shifts from mainly single Pd atoms on the 4 atm% Pd alloy to larger Pd ensembles of at least three atoms for the 8 atm% Pd/Au catalyst. The DFT studies also indicated that the rate-controlling process is different: H 2 (D 2 ) dissociation determines the rate for single atoms whereas recombination of adsorbed H and D determines the rate on Pd trimers, similar to bulk Pd. 2Both experiment and theory suggest that the increased reaction rate with increasing Pd content and ensemble size stems from an entropic driving force. Finally, our results support hydrogen migration between Pd sites via Au and indicate that the dilute alloy design prevents the formation of subsurface hydrogen, which is crucial in achieving high selectivity in hydrogenation catalysis.

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Section: Discussionmentioning

confidence: 94%

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

et al. 2021

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“…Supplementary Note 4 provides an overview and more details are given in review papers 49 , 50 . Examples of its applications in atomistic ripening are in the references 9 , 22 , 51 , 52 .…”

Section: Methodsmentioning

confidence: 99%

Real-time dynamics and structures of supported subnanometer catalysts via multiscale simulations

Wang

Kalscheur

et al. 2021

Nat Commun

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Understanding the performance of subnanometer catalysts and how catalyst treatment and exposure to spectroscopic probe molecules change the structure requires accurate structure determination under working conditions. Experiments lack simultaneous temporal and spatial resolution and could alter the structure, and similar challenges hinder first-principles calculations from answering these questions. Here, we introduce a multiscale modeling framework to follow the evolution of subnanometer clusters at experimentally relevant time scales. We demonstrate its feasibility on Pd adsorbed on CeO2(111) at various catalyst loadings, temperatures, and exposures to CO. We show that sintering occurs in seconds even at room temperature and is mainly driven by free energy reduction. It leads to a kinetically (far from equilibrium) frozen ensemble of quasi-two-dimensional structures that CO chemisorption and infrared experiments probe. CO adsorption makes structures flatter and smaller. High temperatures drive very rapid sintering toward larger, stable/metastable equilibrium structures, where CO induces secondary structure changes only.

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“…In addition, Sykes et al synthesized and tested a kind of PdAu/SiO 2 bimetallic catalyst. 63 Pd 0.02 Au 0.98 SAAs with a Pd/Au atomic ratio of 1/49 were prepared by a sequential reduction method and then supported on SiO 2 (Fig. 5b).…”

Section: Single-atomic Alloys (Saas)mentioning

confidence: 99%

Synergistically enhanced single-atomic site catalysts for clean energy conversion

2022

J. Mater. Chem. A

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

Cited by 116 publications

References 91 publications

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

Real-time dynamics and structures of supported subnanometer catalysts via multiscale simulations

Synergistically enhanced single-atomic site catalysts for clean energy conversion

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