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Marlowe J, Deshpande S, Vlachos DG, Abu-Omar MM, Christopher P. Effect of Dynamic and Preferential Decoration of Pt Catalyst Surfaces by WO x on Hydrodeoxygenation Reactions. J Am Chem Soc 2024; 146:13862-13874. [PMID: 38738663 DOI: 10.1021/jacs.4c00931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
Catalysts containing Pt nanoparticles and reducible transition-metal oxides (WOx, NbOx, TiOx) exhibit remarkable selectivity to aromatic products in hydrodeoxygenation (HDO) reactions for biomass valorization, contrasting the undesired aromatic hydrogenation typically observed for metal catalysts. However, the active site(s) responsible for the high selectivity remains elusive. Here, theoretical and experimental analyses are combined to explain the observed HDO reactivity by interrogating the organization of reduced WOx domains on Pt surfaces at sub-monolayer coverage. The SurfGraph algorithm is used to develop model structures that capture the configurational space (∼1000 configurations) for density functional theory (DFT) calculations of a W3O7 trimer on stepped Pt surfaces. Machine-learning models trained on the DFT calculations identify the preferential occupation of well-coordinated Pt sites (≥8 Pt coordination number) by WOx and structural features governing WOx-Pt stability. WOx/Pt/SiO2 catalysts are synthesized with varying W loadings to test the theoretical predictions and relate them to HDO reactivity. Spectroscopy- and microscopy-based catalyst characterizations identify the dynamic and preferential decoration of well-coordinated sites on Pt nanoparticles by reduced WOx species, consistent with theoretical predictions. The catalytic consequences of this preferential decoration on the HDO of a lignin model compound, dihydroeugenol, are clarified. The effect of WOx decoration on Pt nanoparticles for HDO involves WOx inhibition of aromatic ring hydrogenation by preferentially blocking well-coordinated Pt sites. The identification of preferential decoration on specific sites of late-transition-metal surfaces by reducible metal oxides provides a new perspective for understanding and controlling metal-support interactions in heterogeneous catalysis.
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Affiliation(s)
- Justin Marlowe
- Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Siddharth Deshpande
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States
- Catalysis Center for Energy Innovation, University of Delaware, Newark, Delaware 19716, United States
| | - Dionisios G Vlachos
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States
- Catalysis Center for Energy Innovation, University of Delaware, Newark, Delaware 19716, United States
| | - Mahdi M Abu-Omar
- Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California 93106, United States
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Phillip Christopher
- Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California 93106, United States
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Wang J, Rozycki MT, Tong X, White MG. Aggregation of Size-Selected Oxide Clusters Deposited onto Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:13481-13492. [PMID: 37695694 DOI: 10.1021/acs.langmuir.3c01220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/13/2023]
Abstract
Kinetic Monte Carlo (kMC) simulations along with density functional theory (DFT) calculations were used to investigate the aggregation of size-selected Nb3Oy (y = 5, 6, 7) clusters deposited onto the Au(111) surface. Recent STM experiments showed that the cluster binding sites and sizes of the cluster assemblies on the Nb3Oy/Au(111) surfaces strongly depend on the stoichiometry of the clusters, i.e., the oxygen-to-niobium ratio. To better understand the origins of these differences, kMC simulations of the nucleation and growth of cluster assemblies were performed using energy barriers for diffusion and intercluster interactions estimated from DFT calculations of cluster binding and dimerization energies, respectively. Comparisons of the kMC simulations with STM images of the as-deposited Nb3Oy/Au(111) surfaces at RT and after high temperature annealing were used to further optimize the energetics and gauge the importance of nearest neighbor interactions. The kMC simulations demonstrate that the assembly of Nb3Oy clusters on Au(111) are largely controlled by the magnitude of the barriers for diffusion and interparticle-bond formation, while changes at higher temperatures are sensitive to the binding energies between nearest neighbors. Simulations for the Nb3O5 and Nb3O6 clusters, which exhibit smaller cluster assembly sizes in STM, required larger diffusion barriers as well as different barriers for interparticle binding, which reflected differences in DFT calculated dimerization energies. The results demonstrate the effectiveness of combined DFT and kMC calculations for understanding how the stoichiometry affects the aggregation of small oxide clusters on a metal surface.
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Affiliation(s)
- Jason Wang
- Department of Chemistry, Stony Book University, Stony Brook, New York 11794, United States
| | - Matthew Toledo Rozycki
- Department of Chemistry, Stony Book University, Stony Brook, New York 11794, United States
| | - Xiao Tong
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Michael G White
- Department of Chemistry, Stony Book University, Stony Brook, New York 11794, United States
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States
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Denchy MA, Wang L, Bilik BR, Hansen L, Albornoz S, Lizano F, Blando N, Hicks Z, Gantefoer G, Bowen KH. Ultrasmall Cluster Model for Investigating Single Atom Catalysis: Dehydrogenation of 1-Propanamine by Size-Selected Pt 1Zr 2O 7 Clusters Supported on HOPG. J Phys Chem A 2022; 126:7578-7590. [PMID: 36257817 DOI: 10.1021/acs.jpca.2c03149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The selective dehydrogenation of hydrocarbons and their functionalized derivatives is a promising pathway in the realization of endothermic fuel systems for powering important technologies such as hypersonic aircraft. The recent surge in interest in single atom catalysts (SACs) over the past decade offers the opportunity to achieve the ultimate levels of selectivity through the subnanoscale design tailoring of novel catalysts. Experimental techniques capable of investigating the fundamental nature of the active sites of novel SACs in well-controlled model studies offer the chance to reveal promising insights. We report here an approach to accomplish this through the soft landing of mass-selected, ultrasmall metal oxide cluster ions, in which a single noble metal atom bound to a metal oxide moiety serves as a model SAC active site. This method allows the preparation of model catalysts in which monodispersed neutral SAC model active sites are decorated across an inert electrically conductive support at submonolayer surface coverage, in this case, Pt1Zr2O7 clusters supported on highly oriented pyrolytic graphite (HOPG). The results contained herein show the characterization of the Pt1Zr2O7/HOPG model catalyst by X-ray photoelectron spectroscopy (XPS), along with an investigation of its reactivity toward the functionalized hydrocarbon molecule, 1-propanamine. Through temperature-programmed desorption/reaction (TPD/R) experiments it was shown that Pt1Zr2O7/HOPG decomposes 1-propanamine exclusively into propionitrile and H2, which desorb at 425 and 550 K, respectively. Conversely, clusters without the single platinum atom, that is, Zr2O7/HOPG, exhibited no reactivity toward 1-propanamine. Hence, the single platinum atom in Pt1Zr2O7/HOPG was found to play a critical role in the observed reactivity.
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Affiliation(s)
- Michael A Denchy
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Linjie Wang
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Benjamin R Bilik
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Lucas Hansen
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Sandra Albornoz
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Francisco Lizano
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Nicolas Blando
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Zachary Hicks
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Gerd Gantefoer
- Fachbereich fuer Physik, Universitaet Konstanz, 78457 Konstanz, Germany
| | - Kit H Bowen
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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