Fluxionality of Catalytic Clusters: When It Matters and How to Address It

Zhai, Huanchen; Alexandrova, Anastassia N.

doi:10.1021/acscatal.6b03243

Cited by 189 publications

(218 citation statements)

References 45 publications

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“…However, the global minimum of the surface‐deposited cluster and its changing geometry during the reaction still do not produce an adequate representation of the catalytic system. Recent advances led us to a striking realization that this single structure is not alone in conditions of catalysis, and instead, many structural forms of the cluster are thermally accessible, jointly constituting the nature of the catalyst . We showed that all practically interesting properties of cluster‐decorated interfaces at typical temperatures of catalysis, such as ionization potential, heat capacity, poisoning propensity, sintering tendencies and mechanisms, and catalytic activity and selectivity, are very different if a statistical ensemble of many states is considered, rather than just the global minimum.…”

Section: The Global Minimum Structure Of the Cluster Catalyst: Not Trmentioning

confidence: 96%

“…Always being a nontrivial task, it is truly complicated for surface‐supported cluster catalysts. High temperatures (~300°C in thermal catalysis), coverage with adsorbates, or the presence of electrolyte and electrochemical potential (in electrocatalysis) significantly affect the structure of both the nanocluster (due to its dynamic nature) and the support (by causing defects) . Given that, it is crucial to develop an accurate, yet computationally practical model to describe the system .…”

Section: The Global Minimum Structure Of the Cluster Catalyst: Not Trmentioning

confidence: 99%

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Surface‐supported cluster catalysis: Ensembles of metastable states run the show

Zandkarimi

Alexandrova

2019

WIREs Comput Mol Sci

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It has recently been shown that the dynamic behavior of surface‐supported nanocluster catalysts in realistic reaction conditions defies conventional models used in catalysis. This opens new doors in catalysis by giving more leverage in catalyst design, but also requires a major revision of the understanding of how dynamic heterogeneous catalytic interfaces operate, as well as of the computational approaches of catalyst modeling, and experimental methods of catalyst characterization. Major aspects of the new paradigm include the collective action of many catalyst states that form a statistical ensemble in reaction conditions, the catalytic activity and selectivity being driven by rare and metastable catalyst states, reaction thermodynamics and kinetics being controlled by different states of the catalyst, broken scaling relationships, non‐Arrhenius behaviors, and catalyst dynamic restructuring being an essential part of the reaction mechanism. For computation, this complexity means the departure from the standard density functional theory calculations of reaction mechanisms on a single catalyst structure. For experiment, it calls for the development of operando characterization tools with the per‐site resolution and the ability to find the minority sites that govern the catalytic activity. For catalyst design, the goal becomes the creation of the catalyst state (geometric and electronic) that might not be present in the as‐prepared catalyst, but would develop in the reaction conditions and would have the desired activity then. While cluster catalysts are the most dramatic in their dynamic fluxionality, other amorphous interfaces also exhibit some of it, and thus are also subject to similar paradigm revision. This article is categorized under: Structure and Mechanism > Reaction Mechanisms and Catalysis

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Section: The Global Minimum Structure Of the Cluster Catalyst: Not Trmentioning

confidence: 96%

Section: The Global Minimum Structure Of the Cluster Catalyst: Not Trmentioning

confidence: 99%

Surface‐supported cluster catalysis: Ensembles of metastable states run the show

Zandkarimi

Alexandrova

2019

WIREs Comput Mol Sci

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“…al. have demonstrated the difficulty of this task for even the simpler system of ethane on a metal surface, which required an exhaustive 58 reaction barriers . For this reason, we focus our exploration on just a few key points to capture the signs of selectivity.…”

Section: Computational Sectionmentioning

confidence: 99%

Oxidative Dehydrogenation of Cyclohexane by Cu vs Pd Clusters: Selectivity Control by Specific Cluster Dynamics

Halder

Zhai

et al. 2020

ChemCatChem

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Supported subnanometer clusters can exhibit catalytic properties not observed in their bulk analogues. Partially‐oxidized Pd and Cu clusters are reported to catalyze the oxidative dehydrogenation of cyclohexane with high activity, and with distinctly different selectivity, producing primarily benzene or cyclohexene, respectively. Under the appliedreaction conditions, the structure and oxidation state of the two catalysts evolve differently, which leads to either the desorption of the cyclohexene intermediate or to its deeper dehydrogenation. Under the applied reaction conditions, the initially oxidized Pd and Cu clusters undergo partial reduction, which we show to be required for the selectivity to emerge. Both systems also have thermal access to multiple distinct structural forms yielding statistical ensembles. The structures within these ensembles evolve with the changing nature of the bound reaction intermediates differently for the two metals; the evolution is found pronounced in the Cu clusters, but only modest in Pd. Ultimately, the different selectivity observed experimentally for the Cu versus Pd clusters is controlled by differences in the collective structural and redox dynamics of their ensembles.

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“…The [Ga] 13 sample maintained its tight form (Figure S5 and Movie S1, Supporting Information), whereas the [Ga] 12 sample appeared to be a melted form of the cluster. Such a melted form of the cluster has also been observed in platinum clusters; fluxionality of platinum clusters consisting of several atoms were reported 56–59. Therefore, a 13‐atom platinum cluster [Pt] 13 was prepared and analyzed by the same method using the pyDPA template 52.…”

mentioning

confidence: 95%

Superatomic Gallium Clusters in Dendrimers: Unique Rigidity and Reactivity Depending on their Atomicity

Kambe

Watanabe

et al. 2020

Advanced Materials

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Superatoms have been investigated due to their possible substitution for other elements. The solution‐phase synthesis of superatoms has attracted attention to realize the availability of superatoms. However, the previous approach is basically limited to the formation of a single cluster. Here, superatoms are investigated and the number of valence electrons in these superatoms is changed by designing the number of gallium atoms present. Based on the dendrimer template method, clusters consisting of 3, 12, 13, and other numbers of atoms have been synthesized. The halogen‐like superatomic nature of Ga13 is structurally and electrochemically observed as completely different to the other clusters. The gallium clusters of 13 and 3 atoms, which can fill the 2P and 1P superatomic orbitals, respectively, exhibit different reactivities. The 3‐atom gallium cluster is suggested as being reduced to Ga3H2− due to the lower shift of energy levels in the unoccupied orbitals. The results for these gallium clusters provide candidates for superatoms.

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Fluxionality of Catalytic Clusters: When It Matters and How to Address It

Cited by 189 publications

References 45 publications

Surface‐supported cluster catalysis: Ensembles of metastable states run the show

Surface‐supported cluster catalysis: Ensembles of metastable states run the show

Oxidative Dehydrogenation of Cyclohexane by Cu vs Pd Clusters: Selectivity Control by Specific Cluster Dynamics

Superatomic Gallium Clusters in Dendrimers: Unique Rigidity and Reactivity Depending on their Atomicity

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