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Moxon S, Symington AR, Tse JS, Flitcroft JM, Skelton JM, Gillie LJ, Cooke DJ, Parker SC, Molinari M. Composition-dependent morphologies of CeO 2 nanoparticles in the presence of Co-adsorbed H 2O and CO 2: a density functional theory study. NANOSCALE 2024; 16:11232-11249. [PMID: 38779821 DOI: 10.1039/d4nr01296h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Catalytic activity is affected by surface morphology, and specific surfaces display greater activity than others. A key challenge is to define synthetic strategies to enhance the expression of more active surfaces and to maintain their stability during the lifespan of the catalyst. In this work, we outline an ab initio approach, based on density functional theory, to predict surface composition and particle morphology as a function of environmental conditions, and we apply this to CeO2 nanoparticles in the presence of co-adsorbed H2O and CO2 as an industrially relevant test case. We find that dissociative adsorption of both molecules is generally the most favourable, and that the presence of H2O can stabilise co-adsorbed CO2. We show that changes in adsorption strength with temperature and adsorbate partial pressure lead to significant changes in surface stability, and in particular that co-adsorption of H2O and CO2 stabilizes the {100} and {110} surfaces over the {111} surface. Based on the changes in surface free energy induced by the adsorbed species, we predict that cuboidal nanoparticles are favoured in the presence of co-adsorbed H2O and CO2, suggesting that cuboidal particles should experience a lower thermodynamic driving force to reconstruct and thus be more stable as catalysts for processes involving these species.
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Affiliation(s)
- Samuel Moxon
- Department of Physical and Life Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
| | - Adam R Symington
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Joshua S Tse
- Department of Physical and Life Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
| | - Joseph M Flitcroft
- Department of Chemistry, University of Manchester, Manchester, M13 9PL, UK
| | - Jonathan M Skelton
- Department of Chemistry, University of Manchester, Manchester, M13 9PL, UK
| | - Lisa J Gillie
- Department of Physical and Life Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
| | - David J Cooke
- Department of Physical and Life Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
| | - Stephen C Parker
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Marco Molinari
- Department of Physical and Life Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
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Morgan LM, Loche D, Corrias A, Hayama S, Mountjoy G. Using Ex Situ and In Situ HERFD-XANES to Reveal the Superior Oxidation and Reduction Cycling of Ceria Nanocubes Dispersed in Silica Aerogel. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:19554-19562. [PMID: 37817919 PMCID: PMC10561250 DOI: 10.1021/acs.jpcc.3c03785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 09/07/2023] [Indexed: 10/12/2023]
Abstract
The oxygen storage capacity of ceria-based catalytic materials is influenced by their size, morphology, and surface structure, which can be tuned using surfactant-mediated synthesis. In particular, the cuboidal morphology exposes the most reactive surfaces; however, when the capping agent is removed, the nanocubes can agglomerate and limit the available reactive surface. Here, we study ceria nanocubes, lanthanum-doped ceria nanocubes, and ceria nanocubes embedded inside a highly porous silica aerogel by high-energy resolution fluorescence detection-X-ray absorption near edge spectroscopy at the Ce L3 edge. In situ measurements showed an increased reversibility of redox cycles in ceria nanocubes when embedded in the aerogel, demonstrating enhanced reactivity due to the retention of reactive surfaces. These aerogel nanocomposites show greater improvement in the redox capacity and increased thermal stability of this catalytic material compared to the surfactant-capped nanocubes. Ex situ measurements were also performed to study the effect of lanthanum doping on the cerium oxidation state in the nanocubes, indicating a higher proportion of Ce4+ compared to that of the undoped ceria nanocubes.
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Affiliation(s)
- Lucy M. Morgan
- School
of Chemistry and Forensic Science, University
of Kent, Ingram Building, Canterbury CT2 7NH, U.K.
| | - Danilo Loche
- School
of Chemistry and Forensic Science, University
of Kent, Ingram Building, Canterbury CT2 7NH, U.K.
| | - Anna Corrias
- School
of Chemistry and Forensic Science, University
of Kent, Ingram Building, Canterbury CT2 7NH, U.K.
| | - Shusaku Hayama
- Diamond
Light Source, Harwell Science & Innovation
Campus, Didcot OX11 DE, U.K.
| | - Gavin Mountjoy
- School
of Physics and Astronomy, University of
Kent, Ingram Building, Canterbury CT2 7NH, U.K.
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Pyrolysis Preparation Process of CeO2 with the Addition of Citric Acid: A Fundamental Study. CRYSTALS 2021. [DOI: 10.3390/cryst11080912] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
CeO2 is an important energy storage material that can be used in solid fuel cells. Adding citric acid can improve the particle distribution of the pyrolytic preparation of CeO2 inside the reactor. Through Fluent, this paper investigated the pyrolysis preparation of CeO2 with the addition of citric acid by adopting the Eulerian multiphase flow model, component transportation model, and standard k-ε turbulence model. The experimental and simulation results suggest that the addition of citric acid can alter the pressure, temperature, and component distributions inside the reactor. When the mass fraction of O2 is 0.3, the concentration distribution effect of the CeO2 component is optimal and its conversation rate is the highest. When the mass fraction of citric acid is 0.04, the concentration distribution effect of the CeO2 component is the best, as witnessed by the high CeO2 concentration at the exit. It was found that an O2 content of 30 wt % and citric acid content of 4 wt % were optimal operating conditions for this technology.
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