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Water adsorption and its effect on the stability of low index stoichiometric and reduced surfaces of ceria

Molinari, M., Parker, S.C., Sayle, D.C., Islam, M.S. (2012) Water adsorption and its effect on the stability of low index stoichiometric and reduced surfaces of ceria. Journal of Physical Chemistry C, 116 (12). pp. 7073-7082. ISSN 19327447 (ISSN). (doi:10.1021/jp300576b) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Abstract

The influence of water on the redox properties of ceria is pivotal to its widespread exploitation spanning a variety of applications. Ab initio simulation techniques based on DFT-GGA+U are used to investigate the water-ceria system including associative (H 2O) and dissociative (- OH) adsorption/desorption of water and the formation of oxygen vacancies in the presence of water vapor on the stoichiometric and reduced low index surfaces of ceria at different water coverages. Our calculations address the controversy concerning the adsorption of water on the CeO 2{111}, and new results are reported for the CeO 2{110} and {100} surfaces. The simulations reveal strong water coverage dependence for dissociatively (- OH) adsorbed water on stoichiometric surfaces which becomes progressively destabilized at high coverage, while associative (H 2O) adsorption depends weakly on the coverage due to weaker interactions between the adsorbed molecules. Analysis of the adsorption geometries suggests that the surface cerium atom coordination controls the strong adhesion of water as the average distance Ce-O W is always 10% greater than the Ce-O distance in the bulk, while the hydrogen bonding network dictates the orientation of the molecules. The adsorption energy is predicted to increase on reduced surfaces because oxygen vacancies act as active sites for water dissociation. Crucially, by calculating the heat of reduction of dry and wet surfaces, we also show that water promotes further reduction of ceria surfaces and is therefore central to its redox chemistry. Finally, we show how these simulation approaches can be used to evaluate water desorption as a function of temperature and pressure which accords well with experimental data for CeO 2{111}. We predict desorption temperatures (T D) for CeO 2{110} and CeO 2{100} surfaces, where experimental data are not yet available. Such an understanding will help experiment interpret the complex surface/interface redox processes of ceria, which will, inevitably, include water. © 2012 American Chemical Society.

Item Type: Article
DOI/Identification number: 10.1021/jp300576b
Additional information: Unmapped bibliographic data: LA - English [Field not mapped to EPrints] J2 - J. Phys. Chem. C [Field not mapped to EPrints] AD - Department of Chemistry, University of Bath, Claverton Down, Bath, Avon, BA2 7AY, United Kingdom [Field not mapped to EPrints] AD - Department of Engineering and Applied Science, Cranfield University, Defence Academy of the United Kingdom, Shrivenham, SN6 8LA, United Kingdom [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Uncontrolled keywords: Ab initio simulations, Active site, Adsorbed molecules, Adsorbed water, Adsorption energies, Adsorption geometries, Adsorption of water, Adsorption/desorption, Average Distance, Cerium atoms, Complex surface, Coordination control, Desorption temperatures, DFT-GGA, Dry and wet, Experimental data, Hydrogen bonding network, Influence of water, Low index, Low-index surfaces, New results, Presence of water, Redox chemistry, Redox process, Redox property, Simulation approach, Stoichiometric surfaces, Water adsorption, Water desorption, Water dissociation, Adhesion, Adsorption, Cerium, Cerium compounds, Desorption, Dissociation, Oxygen vacancies, Dewatering
Subjects: Q Science
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Dean Sayle
Date Deposited: 27 Jan 2015 16:19 UTC
Last Modified: 29 May 2019 14:06 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/46778 (The current URI for this page, for reference purposes)
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