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Qiu C, Odarchenko Y, Meng Q, Dong H, Gonzalez IL, Panchal M, Olalde-Velasco P, Maccherozzi F, Zanetti-Domingues L, Martin-Fernandez ML, Beale AM. Compositional Evolution of Individual CoNPs on Co/TiO 2 during CO and Syngas Treatment Resolved through Soft XAS/X-PEEM. ACS Catal 2023; 13:15956-15966. [PMID: 38125980 PMCID: PMC10729030 DOI: 10.1021/acscatal.3c03214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 11/08/2023] [Accepted: 11/13/2023] [Indexed: 12/23/2023]
Abstract
The nanoparticle (NP) redox state is an important parameter in the performance of cobalt-based Fischer-Tropsch synthesis (FTS) catalysts. Here, the compositional evolution of individual CoNPs (6-24 nm) in terms of the oxide vs metallic state was investigated in situ during CO/syngas treatment using spatially resolved X-ray absorption spectroscopy (XAS)/X-ray photoemission electron microscopy (X-PEEM). It was observed that in the presence of CO, smaller CoNPs (i.e., ≤12 nm in size) remained in the metallic state, whereas NPs ≥ 15 nm became partially oxidized, suggesting that the latter were more readily able to dissociate CO. In contrast, in the presence of syngas, the oxide content of NPs ≥ 15 nm reduced, while it increased in quantity in the smaller NPs; this reoxidation that occurs primarily at the surface proved to be temporary, reforming the reduced state during subsequent UHV annealing. O K-edge measurements revealed that a key parameter mitigating the redox behavior of the CoNPs were proximate oxygen vacancies (Ovac). These results demonstrate the differences in the reducibility and the reactivity of Co NP size on a Co/TiO2 catalyst and the effect Ovac have on these properties, therefore yielding a better understanding of the physicochemical properties of this popular choice of FTS catalysts.
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Affiliation(s)
- Chengwu Qiu
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Research
Complex at Harwell (RCaH), Harwell, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Yaroslav Odarchenko
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Research
Complex at Harwell (RCaH), Harwell, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Qingwei Meng
- School
of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006 (China)
| | - Hongyang Dong
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Research
Complex at Harwell (RCaH), Harwell, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Ines Lezcano Gonzalez
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Research
Complex at Harwell (RCaH), Harwell, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Monik Panchal
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Research
Complex at Harwell (RCaH), Harwell, Didcot, Oxfordshire OX11 0FA, U.K.
| | | | | | | | | | - Andrew M. Beale
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Research
Complex at Harwell (RCaH), Harwell, Didcot, Oxfordshire OX11 0FA, U.K.
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Qiu C, Odarchenko Y, Meng Q, Xu S, Lezcano-Gonzalez I, Olalde-Velasco P, Maccherozzi F, Zanetti-Domingues L, Martin-Fernandez M, Beale AM. Resolving the Effect of Oxygen Vacancies on Co Nanostructures Using Soft XAS/X-PEEM. ACS Catal 2022; 12:9125-9134. [PMID: 35966607 PMCID: PMC9361287 DOI: 10.1021/acscatal.2c00611] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 06/28/2022] [Indexed: 11/28/2022]
Abstract
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Improving both the extent of metallic Co nanoparticle
(Co NP) formation
and their stability is necessary to ensure good catalytic performance,
particularly for Fischer–Tropsch synthesis (FTS). Here, we
observe how the presence of surface oxygen vacancies (Ovac) on TiO2 can readily reduce individual Co3O4 NPs directly into CoO/Co0 in the freshly
prepared sample by using a combination of X-ray photoemission electron
microscopy (X-PEEM) coupled with soft X-ray absorption spectroscopy.
The Ovac are particularly good at reducing the edge of
the NPs as opposed to their center, leading to smaller particles being
more reduced than larger ones. We then show how further reduction
(and Ovac consumption) is achieved during heating in H2/syngas (H2 + CO) and reveal that Ovac also prevents total reoxidation of Co NPs in syngas, particularly
the smallest (∼8 nm) particles, thus maintaining the presence
of metallic Co, potentially improving catalyst performance.
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Affiliation(s)
- Chengwu Qiu
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Research Complex at Harwell (RCaH), Harwell, Didcot OX11 0FA, Oxfordshire, U.K
| | - Yaroslav Odarchenko
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Research Complex at Harwell (RCaH), Harwell, Didcot OX11 0FA, Oxfordshire, U.K
| | - Qingwei Meng
- School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China
| | - Shaojun Xu
- Research Complex at Harwell (RCaH), Harwell, Didcot OX11 0FA, Oxfordshire, U.K
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff CF10 3AT, U.K
| | - Ines Lezcano-Gonzalez
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Research Complex at Harwell (RCaH), Harwell, Didcot OX11 0FA, Oxfordshire, U.K
| | | | | | | | | | - Andrew M. Beale
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Research Complex at Harwell (RCaH), Harwell, Didcot OX11 0FA, Oxfordshire, U.K
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Vaz CAF, Balan A, Nolting F, Kleibert A. In situ magnetic and electronic investigation of the early stage oxidation of Fe nanoparticles using X-ray photo-emission electron microscopy. Phys Chem Chem Phys 2014; 16:26624-30. [DOI: 10.1039/c4cp02725f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In situX-ray photoemission electron microscopy reveals the evolution of chemical composition and magnetism of individual iron nanoparticles during oxidation.
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Affiliation(s)
- C. A. F. Vaz
- Swiss Light Source
- Paul Scherrer Institut
- 5232 Villigen PSI, Switzerland
| | - A. Balan
- Swiss Light Source
- Paul Scherrer Institut
- 5232 Villigen PSI, Switzerland
| | - F. Nolting
- Swiss Light Source
- Paul Scherrer Institut
- 5232 Villigen PSI, Switzerland
| | - A. Kleibert
- Swiss Light Source
- Paul Scherrer Institut
- 5232 Villigen PSI, Switzerland
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Fraile Rodríguez A, Kleibert A, Bansmann J, Voitkans A, Heyderman LJ, Nolting F. Size-dependent spin structures in iron nanoparticles. PHYSICAL REVIEW LETTERS 2010; 104:127201. [PMID: 20366559 DOI: 10.1103/physrevlett.104.127201] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Indexed: 05/27/2023]
Abstract
Using photoemission electron microscopy, we study the magnetization orientation in single 5-25 nm iron particles coupled to a ferromagnetic cobalt support. We find a noncollinear alignment between the particle and substrate magnetization above a particle size of approximately 6 nm and a parallel alignment for smaller sizes. Numerical calculations reveal a transition from an exchange-dominated to an anisotropy-dominated regime on increasing the particle height: the smaller particles are in a single-domain collinear state while larger particles exhibit a spin-spiral magnetic structure determined by the magnetic anisotropy energy.
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Maul J. Measurement of nanoparticle mass distributions by laser desorption/ionization time-of-flight mass spectrometry. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:176216. [PMID: 21690961 DOI: 10.1088/0953-8984/19/17/176216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this paper, access to the mass distribution analysis of nanoparticles is described based on laser desorption/ionization and time of flight mass spectrometry. Two examples are given, demonstrating the accurate mass distribution analysis of nanoparticles fabricated both ex situ and in situ during the laser-assisted desorption process. The potentials and the limitations of the method are discussed, with special emphasis on carbonaceous clusters and molecules.
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Affiliation(s)
- Jochen Maul
- Institut für Physik, Staudingerweg 7, Johannes Gutenberg-Universität, 55128 Mainz, Germany
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Ratto F, Locatelli A, Fontana S, Kharrazi S, Ashtaputre S, Kulkarni SK, Heun S, Rosei F. Chemical mapping of individual semiconductor nanostructures. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2006; 2:401-5. [PMID: 17193059 DOI: 10.1002/smll.200500345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We demonstrate experimentally the power of a novel analytical tool for X-ray spectromicroscopy. This provides a minimally intrusive elemental mapping of surfaces at the nanoscale and holds the promise of remarkable versatility. We have applied our procedure to the characterization of Ge(Si) islands on Si(111) substrates, with the aim of investigating the surface stoichiometry gradients and gaining insight into the intermixing dynamics. By identifying Si-richer edges with respect to the centers, we are able to associate alloying in these islands to surface transport processes.
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Affiliation(s)
- Fulvio Ratto
- INRS Energie, Matériaux et Télécommunications, Université du Québec, 1650 Boul. Lionel Boulet, J3X 1S2 Varennes, QC, Canada
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