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Zhang Z, Filez M, Solano E, Poonkottil N, Li J, Minjauw MM, Poelman H, Rosenthal M, Brüner P, Galvita VV, Detavernier C, Dendooven J. Controlling Pt nanoparticle sintering by sub-monolayer MgO ALD thin films. NANOSCALE 2024; 16:5362-5373. [PMID: 38375669 DOI: 10.1039/d3nr05884k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
Metal nanoparticle (NP) sintering is a major cause of catalyst deactivation, as NP growth reduces the surface area available for reaction. A promising route to halt sintering is to deposit a protective overcoat on the catalyst surface, followed by annealing to generate overlayer porosity for gas transport to the NPs. Yet, such a combined deposition-annealing approach lacks structural control over the cracked protection layer and the number of NP surface atoms available for reaction. Herein, we exploit the tailoring capabilities of atomic layer deposition (ALD) to deposit MgO overcoats on archetypal Pt NP catalysts with thicknesses ranging from sub-monolayers to nm-range thin films. Two different ALD processes are studied for the growth of MgO overcoats on Pt NPs anchored on a SiO2 support, using Mg(EtCp)2 and H2O, and Mg(TMHD)2 and O3, respectively. Spectroscopic ellipsometry and X-ray photoelectron spectroscopy measurements reveal significant growth on both SiO2 and Pt for the former process, while the latter exhibits a drastically lower growth per cycle with an initial chemical selectivity towards Pt. These differences in MgO growth characteristics have implications for the availability of uncoated Pt surface atoms at different stages of the ALD process, as probed by low energy ion scattering, and for the sintering behavior during O2 annealing, as monitored in situ with grazing incidence small angle X-ray scattering (in situ GISAXS). The Mg(TMHD)2-O3 ALD process enables exquisite coverage control allowing a balance between physically blocking the Pt surface to prevent sintering and keeping Pt surface atoms free for reaction. This approach avoids the need for post-annealing, hence also safeguarding the structural integrity of the as-deposited overcoat.
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Affiliation(s)
- Zhiwei Zhang
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
| | - Matthias Filez
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
- Centre for Membrane Separations Adsorption Catalysis and Spectroscopy for Sustainable Solutions (cMACS), KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Eduardo Solano
- NCD-SWEET beamline, ALBA synchrotron light source, Carrer de la Llum 2-26, 08290, Cerdanyola del Vallès, Spain
| | - Nithin Poonkottil
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
| | - Jin Li
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
| | - Matthias M Minjauw
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
| | - Hilde Poelman
- Laboratory for Chemical Technology, Ghent University, Technologiepark 125, 9052 Ghent, Belgium
| | - Martin Rosenthal
- DUBBLE beamline, ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Philipp Brüner
- IONTOF Technologies GmbH, Heisenbergstr. 15, 48149 Muenster, Germany
| | - Vladimir V Galvita
- Laboratory for Chemical Technology, Ghent University, Technologiepark 125, 9052 Ghent, Belgium
| | - Christophe Detavernier
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
| | - Jolien Dendooven
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
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Filez M, Walke P, Le-The H, Toyouchi S, Peeters W, Tomkins P, Eijkel JCT, De Feyter S, Detavernier C, De Vos DE, Uji-I H, Roeffaers MBJ. Nanoscale Chemical Diversity of Coke Deposits on Nanoprinted Metal Catalysts Visualized by Tip-Enhanced Raman Spectroscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2305984. [PMID: 37938141 DOI: 10.1002/adma.202305984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 10/31/2023] [Indexed: 11/09/2023]
Abstract
Coke formation is the prime cause of catalyst deactivation, where undesired carbon wastes block the catalyst surface and hinder further reaction in a broad gamut of industrial chemical processes. Yet, the origins of coke formation and their distribution across the catalyst remain elusive, obstructing the design of coke-resistant catalysts. Here, the first-time application of tip-enhanced Raman spectroscopy (TERS) is demonstrated as a nanoscale chemical probe to localize and identify coke deposits on a post-mortem metal nanocatalyst. Monitoring coke at the nanoscale circumvents bulk averaging and reveals the local nature of coke with unmatched detail. The nature of coke is chemically diverse and ranges from nanocrystalline graphite to disordered and polymeric coke, even on a single nanoscale location of a top-down nanoprinted SiO2 -supported Pt catalyst. Surprisingly, not all Pt is an equal producer of coke, where clear isolated coke "hotspots" are present non-homogeneously on Pt which generate large amounts of disordered coke. After their formation, coke shifts to the support and undergoes long-range transport on the surrounding SiO2 surface, where it becomes more graphitic. The presented results provide novel guidelines to selectively free-up the coked metal surface at more mild rejuvenation conditions, thus securing the long-term catalyst stability.
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Affiliation(s)
- Matthias Filez
- Centre for Membrane Separations, Adsorption, Catalysis and Spectroscopy for Sustainable Solutions (cMACS), KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, Ghent, 9000, Belgium
| | - Peter Walke
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
| | - Hai Le-The
- BIOS Lab-on-a-Chip Group, MESA+ Institute, University of Twente, Enschede, NB, 7522, The Netherlands
| | - Shuichi Toyouchi
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
| | - Wannes Peeters
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
| | - Patrick Tomkins
- Centre for Membrane Separations, Adsorption, Catalysis and Spectroscopy for Sustainable Solutions (cMACS), KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
| | - Jan C T Eijkel
- BIOS Lab-on-a-Chip Group, MESA+ Institute, University of Twente, Enschede, NB, 7522, The Netherlands
| | - Steven De Feyter
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
| | - Christophe Detavernier
- Conformal Coating of Nanomaterials (CoCooN), Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, Ghent, 9000, Belgium
| | - Dirk E De Vos
- Centre for Membrane Separations, Adsorption, Catalysis and Spectroscopy for Sustainable Solutions (cMACS), KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
| | - Hiroshi Uji-I
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
- Research Institute for Electronic Science (RIES), Hokkaido University, Sapporo, Hokkaido, 001-0020, Japan
- Division of Information Science and Technology, Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Hokkaido, 060-0814, Japan
| | - Maarten B J Roeffaers
- Centre for Membrane Separations, Adsorption, Catalysis and Spectroscopy for Sustainable Solutions (cMACS), KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
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