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A kinetic model of water adsorption, clustering and dissociation on the Fe3S4{001} surface

Roldan Martinez, Alberto and De Leeuw, Nora 2017. A kinetic model of water adsorption, clustering and dissociation on the Fe3S4{001} surface. Physical Chemistry Chemical Physics 19 , pp. 12045-12055. 10.1039/C6CP07371A

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Abstract

The interaction of water with catalyst surfaces is a common process which requires investigation. Here, we have employed density functional theory calculations to investigate the adsorption of up to ten water molecules on the {001} surface of greigite (Fe3S4), which owing to its redox properties, is of increasing interest as a catalyst, e.g. in electro-catalysis. We have systematically analyzed and characterized the modes of water adsorption on the surface, where we have considered both molecular and dissociative adsorption processes. The calculations show that molecular adsorption is the predominant state on these surfaces, from both a thermodynamic and kinetic point of view. We have explored the molecular dispersion on the surface under different coverages and found that the orientation of the molecule, and therefore the surface dipole, depends on the number of adsorbed molecules. The interactions between the water molecules become stronger with an increasing number of water molecules, following an exponential decay which tends to the interaction energy found in bulk water. We have also shown the evolution of the infra-red signals as a function of water coverage relating to the H-bond networks formed on the surface. Next we have included these results in a classical micro-kinetic model, which introduced the effects of temperature in the simulations, thus helping us to derive the water cluster size on the greigite surface as a function of the initial conditions of pressure, temperature and external potential. The kinetic model concluded that water molecules agglomerate in clusters instead of wetting the surface, which agrees with the low hydrophilicity of Fe3S4. Clusters consisting of four water molecules was shown to be the most stable cluster under a wide range of temperatures and external potential.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Advanced Research Computing @ Cardiff (ARCCA)
Cardiff Catalysis Institute (CCI)
Chemistry
Subjects: Q Science > QD Chemistry
Uncontrolled Keywords: Iron Sulfide, Magnetite, Micro-kinetics, Solid-Water Interface, Synergistic Adsorption
Publisher: Royal Society of Chemistry
ISSN: 1463-9076
Funders: Engineering & Physical Sciences Research Council
Date of First Compliant Deposit: 6 June 2017
Date of Acceptance: 3 April 2017
Last Modified: 29 May 2018 18:45
URI: http://orca-mwe.cf.ac.uk/id/eprint/101186

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