Kinetic Isolation between Turnovers on Au 18 Nanoclusters: Formic Acid Decomposition One Molecule at a Time

Chen, Benjamin W.  J.; Stamatakis, Michail; Mavrikakis, Manos

doi:10.1021/acscatal.9b02167

Title: Kinetic Isolation between Turnovers on Au ₁₈ Nanoclusters: Formic Acid Decomposition One Molecule at a Time

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Abstract

Formic acid (HCOOH or FA) is a clean, safe, and renewable hydrogen storage material. Although Au catalysts decompose vapor-phase FA with high activity and selectivity toward hydrogen, the active site and reaction mechanism remain unclear. Here, we show that the subnanometric Au₁₈ cluster (0.8 nm in diameter) is likely the active species for FA decomposition. We performed coverage self-consistent, density functional theory-based kinetic Monte Carlo simulations of FA decomposition on gas-phase Au18 clusters, predicting 100% selectivity toward hydrogen and turnover frequencies close to experimentally determined values. The active site is made up of a triangular ensemble of three atoms each possessing a coordination number of 5. Although there are two active site ensembles on the Au18 cluster, their occupations are strongly correlated because of strong, stabilizing interactions between pairs of open-shell adsorbates mediated by the superatomic nature of the cluster. Because the occupation of the active sites blocks the dissociation of additional HCOOH molecules, there is kinetic isolation between turnovers: only one HCOOH molecule can dissociate on the cluster at a time. This explains the extraordinary, experimentally observed selectivity of Au catalysts toward HD during decomposition of HCOOD and DCOOH. Our work offers nanoscale insights into the reaction mechanisms ofmore »« less

Authors:

Chen, Benjamin W. J. ^[1];

^[2];

^[1]

Univ. of Wisconsin, Madison, WI (United States). Dept. of Chemical and Biological Engineering
Univ. College London (UCL), London (United Kingdom). Thomas Young Centre and Dept. of Chemical Engineering

Publication Date:: Wed Sep 04 00:00:00 EDT 2019

Research Org.:: Univ. of Wisconsin, Madison, WI (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:: 1569465

Grant/Contract Number:: FG02-05ER15731; AC02-05CH11231; AC02-06CH11357

Resource Type:: Accepted Manuscript

Journal Name:: ACS Catalysis

Additional Journal Information:: Journal Volume: 9; Journal Issue: 10; Journal ID: ISSN 2155-5435

Publisher:: American Chemical Society (ACS)

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

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                    Chen, Benjamin W.  J., Stamatakis, Michail, and Mavrikakis, Manos. Kinetic Isolation between Turnovers on Au 18 Nanoclusters: Formic Acid Decomposition One Molecule at a Time.  United States: N. p., 2019. 
Web.  doi:10.1021/acscatal.9b02167.

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                    Chen, Benjamin W.  J., Stamatakis, Michail, & Mavrikakis, Manos. Kinetic Isolation between Turnovers on Au 18 Nanoclusters: Formic Acid Decomposition One Molecule at a Time.  United States.  https://doi.org/10.1021/acscatal.9b02167

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                    Chen, Benjamin W.  J., Stamatakis, Michail, and Mavrikakis, Manos. Wed .  
"Kinetic Isolation between Turnovers on Au 18 Nanoclusters: Formic Acid Decomposition One Molecule at a Time".  United States.  https://doi.org/10.1021/acscatal.9b02167.  https://www.osti.gov/servlets/purl/1569465.

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@article{osti_1569465,

  title        = {Kinetic Isolation between Turnovers on Au 18 Nanoclusters: Formic Acid Decomposition One Molecule at a Time},

  author       = {Chen, Benjamin W.  J. and Stamatakis, Michail and Mavrikakis, Manos},

  abstractNote = {Formic acid (HCOOH or FA) is a clean, safe, and renewable hydrogen storage material. Although Au catalysts decompose vapor-phase FA with high activity and selectivity toward hydrogen, the active site and reaction mechanism remain unclear. Here, we show that the subnanometric Au18 cluster (0.8 nm in diameter) is likely the active species for FA decomposition. We performed coverage self-consistent, density functional theory-based kinetic Monte Carlo simulations of FA decomposition on gas-phase Au18 clusters, predicting 100% selectivity toward hydrogen and turnover frequencies close to experimentally determined values. The active site is made up of a triangular ensemble of three atoms each possessing a coordination number of 5. Although there are two active site ensembles on the Au18 cluster, their occupations are strongly correlated because of strong, stabilizing interactions between pairs of open-shell adsorbates mediated by the superatomic nature of the cluster. Because the occupation of the active sites blocks the dissociation of additional HCOOH molecules, there is kinetic isolation between turnovers: only one HCOOH molecule can dissociate on the cluster at a time. This explains the extraordinary, experimentally observed selectivity of Au catalysts toward HD during decomposition of HCOOD and DCOOH. Our work offers nanoscale insights into the reaction mechanisms of FA decomposition over Au. This represents a rare example of heterogeneous catalysis by a cluster that catalyzes reactants one molecule at a time. Our work on Au18 thus sheds light on how the unique electronic properties of subnanometric clusters can be used to design quasi-molecular catalysts with high activity and selectivity.},

  doi          = {10.1021/acscatal.9b02167},

  journal      = {ACS Catalysis},

  number       = 10,

  volume       = 9,

  place        = {United States},

  year         = {Wed Sep 04 00:00:00 EDT 2019},

  month        = {Wed Sep 04 00:00:00 EDT 2019}

}

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Title: Kinetic Isolation between Turnovers on Au 18 Nanoclusters: Formic Acid Decomposition One Molecule at a Time

Abstract

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Title: Kinetic Isolation between Turnovers on Au ₁₈ Nanoclusters: Formic Acid Decomposition One Molecule at a Time