Enhancing the oxygen vacancy formation and migration in bulk chromium(iii) oxide by alkali metal doping: a change from isotropic to anisotropic oxygen diffusion

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dc.contributor.author Carey, John J.
dc.contributor.author Nolan, Michael
dc.date.accessioned 2017-11-02T12:29:50Z
dc.date.available 2017-11-02T12:29:50Z
dc.date.issued 2017-07-11
dc.identifier.citation Carey, J. J. and Nolan, M. (2017) 'Enhancing the oxygen vacancy formation and migration in bulk chromium(iii) oxide by alkali metal doping: a change from isotropic to anisotropic oxygen diffusion', Journal of Materials Chemistry A, 5(30), pp. 15613-15630. doi: 10.1039/C7TA00315C en
dc.identifier.volume 5 en
dc.identifier.issued 30 en
dc.identifier.startpage 15613 en
dc.identifier.endpage 15630 en
dc.identifier.issn 2050-7488
dc.identifier.uri http://hdl.handle.net/10468/4948
dc.identifier.doi 10.1039/C7TA00315C
dc.description.abstract Oxygen vacancy formation and migration are vital properties for reducible oxides such as TiO2, CeO2 and Cr2O3 as the oxygen storage capacity (OSC) of these materials are important for a wide range of applications in photovoltaics, oxidative catalysis and solid oxide fuel cells. Substitutional doping these transition metal oxides enhances their OSC potential, in particular for oxygenation and surface reaction chemistry. This study uses density functional theory with on-site Coulomb interactions (PBE+U) for Cr 3d states (+U = 5 eV) and O 2p states (+U = 5.5 eV) to calculate the oxygen vacancy formation energy and oxygen diffusion pathways for alkali metal (Li, K, Na, Rb) doping of bulk chromium(III) oxide (α-Cr2O3). Substitutional doping of the lattice Cr3+ cations with alkali metals that have a +1 oxidation state, creates two hole states on the neighbouring lattice O atoms, and removal of a lattice oxygen charge compensates the dopants by filling the holes. The removal of the next oxygen describes the reducibility of doped Cr2O3. The oxygen vacancy formation energy is greatly promoted by the alkali dopants with a correlation between the ionic radius of the dopant cation and vacancy formation energy; larger dopants (K, Rb) improve the reducibility more than the smaller dopants (Li, Na). The activation barriers for oxygen migration along different directions in the alkali metal doped Cr2O3 bulk were also calculated to examine the effect of doping on the oxygen migration. The calculated activation energies for the undoped chromia are symmetric in three dimensions (isotropic) and the presence of the dopants break this isotropy. Alkali dopants promote oxygen migration in the oxygen intra-layers while suppressing oxygen migration across the Cr cation layers. The smaller dopants (Li, Na) facilitate easier migration in the oxygen intra-layers to a greater extent than the larger dopants (K, Rb). The Na–Cr2O3 bulk promotes both oxygen vacancy formation and migration which makes it a novel candidate for anode materials in medium temperature SOFCs and battery applications. en
dc.description.sponsorship Science Foundation Ireland and Higher Education Authority (SFI/HEA funded Irish Centre for High-end Computing (ICHEC) and SFI funded local clusters at Tyndall); European Commission (European Cooperation in Science and Technology COST Action CM1104 “Reducible Metal Oxides, Structure and Function”) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Royal Society of Chemistry en
dc.rights © The Royal Society of Chemistry 2017. This is the Accepted Manuscript version of a published work that appeared in final form in Journal of Materials Chemistry A. To access the final published version of record, see http://pubs.rsc.org/en/content/articlepdf/2017/ta/c7ta00315c en
dc.subject Activation energy en
dc.subject Anodes en
dc.subject Chemical activation en
dc.subject ChromiumDensity functional theory en
dc.subject Diffusion in gases en
dc.subject Doping (additives) en
dc.subject Fuel cells en
dc.subject Fuel storage en
dc.subject Lithium en
dc.subject Metals en
dc.subject Oxygen en
dc.subject Positive ions en
dc.subject Solid oxide fuel cells (SOFC) en
dc.subject Surface reactions en
dc.subject Transition metal compounds en
dc.subject Transition metals en
dc.subject Oxygen vacancies en
dc.subject Activation barriers en
dc.subject Alkali metal doping en
dc.subject Battery applications en
dc.subject Oxygen storage capacity en
dc.subject Oxygen vacancy formation energies en
dc.subject Reaction chemistry en
dc.subject Transition-metal oxides en
dc.subject Vacancy formation energies en
dc.title Enhancing the oxygen vacancy formation and migration in bulk chromium(iii) oxide by alkali metal doping: a change from isotropic to anisotropic oxygen diffusion en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Michael Nolan, Tyndall Theory Modelling & Design Centre, University College Cork, Cork, Ireland. +353-21-490-3000 Email: michael.nolan@tyndall.ie en
dc.internal.availability Full text available en
dc.check.info Access to this article is restricted for 12 months after publication by request of the publisher. en
dc.check.date 2018-07-11
dc.date.updated 2017-11-02T12:19:09Z
dc.description.version Accepted Version en
dc.internal.rssid 417268040
dc.contributor.funder European Commission en
dc.contributor.funder Seventh Framework Programme en
dc.contributor.funder Science Foundation Ireland en
dc.contributor.funder Higher Education Authority en
dc.contributor.funder European Cooperation in Science and Technology en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Journal of Materials Chemistry A en
dc.internal.copyrightchecked No !!CORA!! en
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress michael.nolan@tyndall.ie en
dc.relation.project info:eu-repo/grantAgreement/EC/FP7::SP1::NMP/604296/EU/Catalytic Partial Oxidation of Bio Gas and Reforming of Pyrolysis Oil (Bio Oil) for an Autothermal Synthesis Gas Production and Conversion into Fuels/BIOGO-FOR-PRODUCTION en

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