eprintid: 1436734 rev_number: 50 eprint_status: archive userid: 608 dir: disk0/01/43/67/34 datestamp: 2014-08-05 00:36:47 lastmod: 2021-09-20 00:13:34 status_changed: 2014-08-18 10:30:07 type: article metadata_visibility: show item_issues_count: 0 creators_name: Santos-Carballal, D creators_name: Roldan, A creators_name: Grau-Crespo, R creators_name: de Leeuw, NH title: A DFT study of the structures, stabilities and redox behaviour of the major surfaces of magnetite Fe3O4 ispublished: pub divisions: UCL divisions: B04 divisions: C06 note: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/). abstract: The renewed interest in magnetite (Fe3O4) as a major phase in different types of catalysts has led us to study the oxidation–reduction behaviour of its most prominent surfaces. We have employed computer modelling techniques based on the density functional theory to calculate the geometries and surface free energies of a number of surfaces at different compositions, including the stoichiometric plane, and those with a deficiency or excess of oxygen atoms. The most stable surfaces are the (001) and (111), leading to a cubic Fe3O4 crystal morphology with truncated corners under equilibrium conditions. The scanning tunnelling microscopy images of the different terminations of the (001) and (111) stoichiometric surfaces were calculated and compared with previous reports. Under reducing conditions, the creation of oxygen vacancies in the surface leads to the formation of reduced Fe species in the surface in the vicinity of the vacant oxygen. The (001) surface is slightly more prone to reduction than the (111), due to the higher stabilisation upon relaxation of the atoms around the oxygen vacancy, but molecular oxygen adsorbs preferentially at the (111) surface. In both oxidized surfaces, the oxygen atoms are located on bridge positions between two surface iron atoms, from which they attract electron density. The oxidised state is thermodynamically favourable with respect to the stoichiometric surfaces under ambient conditions, although not under the conditions when bulk Fe3O4 is thermodynamically stable with respect to Fe2O3. This finding is important in the interpretation of the catalytic properties of Fe3O4 due to the presence of oxidised species under experimental conditions. date: 2014-10-21 official_url: http://dx.doi.org/10.1039/c4cp00529e vfaculties: VMPS oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green article_type_text: Article verified: verified_manual elements_source: crossref elements_id: 967286 doi: 10.1039/c4cp00529e lyricists_name: De Leeuw, Nora lyricists_name: Grau-Crespo, Ricardo lyricists_name: Roldan Martinez, Alberto lyricists_name: Santos Carballal, David lyricists_id: NHDEL32 lyricists_id: RGRAU87 lyricists_id: AROLD86 lyricists_id: DSANT47 full_text_status: public publication: Physical Chemistry Chemical Physics volume: 16 number: 39 pagerange: 21082-21097 issn: 1463-9076 citation: Santos-Carballal, D; Roldan, A; Grau-Crespo, R; de Leeuw, NH; (2014) A DFT study of the structures, stabilities and redox behaviour of the major surfaces of magnetite Fe3O4. Physical Chemistry Chemical Physics , 16 (39) pp. 21082-21097. 10.1039/c4cp00529e <https://doi.org/10.1039/c4cp00529e>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/1436734/1/Santos-Carballa_c4cp00529e.pdf document_url: https://discovery.ucl.ac.uk/id/eprint/1436734/2/Santos-Carballa_c4cp00529e_Suppl.pdf