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LaFeO₃ as a base material for cathode applications in intermediate temperature solid oxide fuel cells

Taylor, Felicity H; (2019) LaFeO₃ as a base material for cathode applications in intermediate temperature solid oxide fuel cells. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Computational techniques have been employed to perform an in-depth study into the defect chemistry of LaFeO₃, a mixed ionic electronic conductor and a promising candidate for intermediate temperature solid oxide fuel cell cathode applications. Initially, a range of isolated point defects and disorder schemes were considered, from which we established the favourable formation of cation and oxygen vacancies, under oxygen rich and oxygen poor conditions respectively. Schottky disorder also plays an important role in the defect chemistry of LaFeO₃ and the defect model we propose was verified through comparison with experimental work on the oxygen non-stoichiometry of LaFeO₃. Work on the activation energy of oxide ion migration through LaFeO₃ considered three pathways, due to two inequivalent oxygen sites being present in orthorhombic LaFeO₃. The pathways between the O1 and O2 and O2 and O2 sites were found to be the most favourable, having low activation energies in line with experimental results. A range of divalent dopants were then considered, for both the A- and B-sites, with strontium, calcium and manganese showing promising results as A-site dopants, due to low solution and binding energies, while cobalt and nickel showed promising results as B-site dopants. We finished by considering two terminations of the (001) surface of LaFeO₃: FeO₂ and LaO. We found that although the LaO terminated surface has the lowest surface energy, the FeO₂ terminated surface is most defective, with cation vacancies and oxygen vacancies having low formation energies. The FeO₂ terminated surface, therefore, is likely to be more catalytically active than the LaO terminated surface. Two techniques have been used throughout this work, interatomic potential-based methods and DFT-based methods, the results from each are compared throughout.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: LaFeO₃ as a base material for cathode applications in intermediate temperature solid oxide fuel cells
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/ 4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10071230
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