Structure of the catalytic sites in Fe/N/C-catalysts for O-2-reduction in PEM fuel cells

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dc.contributor.authorKramm, Ulrike I.
dc.contributor.authorHerranz, Juan
dc.contributor.authorLarouche, Nicholas
dc.contributor.authorArruda, Thomas M.
dc.contributor.authorLefèvre, Michel
dc.contributor.authorJaouen, Frédéric
dc.contributor.authorBogdanoff, Peter
dc.contributor.authorFiechter, Sebastian
dc.contributor.authorAbs-Wurmbach, Irmgard
dc.contributor.authorMukerjee, Sanjeev
dc.contributor.authorDodelet, Jean-Pol
dc.date.accessioned2016-06-28T06:13:29Z
dc.date.available2016-06-28T06:13:29Z
dc.date.issued2012
dc.descriptionDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.de
dc.descriptionThis publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.en
dc.description.abstractFe-based catalytic sites for the reduction of oxygen in acidic medium have been identified by 57Fe Mössbauer spectroscopy of Fe/N/C catalysts containing 0.03 to 1.55 wt% Fe, which were prepared by impregnation of iron acetate on carbon black followed by heat-treatment in NH3 at 950 °C. Four different Fe-species were detected at all iron concentrations: three doublets assigned to molecular FeN4-like sites with their ferrous ions in a low (D1), intermediate (D2) or high (D3) spin state, and two other doublets assigned to a single Fe-species (D4 and D5) consisting of surface oxidized nitride nanoparticles (FexN, with x ≤ 2.1). A fifth Fe-species appears only in those catalysts with Fe-contents ≥0.27 wt%. It is characterized by a very broad singlet, which has been assigned to incomplete FeN4-like sites that quickly dissolve in contact with an acid. Among the five Fe-species identified in these catalysts, only D1 and D3 display catalytic activity for the oxygen reduction reaction (ORR) in the acid medium, with D3 featuring a composite structure with a protonated neighbour basic nitrogen and being by far the most active species, with an estimated turn over frequency for the ORR of 11.4 e− per site per s at 0.8 V vs. RHE. Moreover, all D1 sites and between 1/2 and 2/3 of the D3 sites are acid-resistant. A scheme for the mechanism of site formation upon heat-treatment is also proposed. This identification of the ORR-active sites in these catalysts is of crucial importance to design strategies to improve the catalytic activity and stability of these materials.en
dc.identifier.eissn1463-9076
dc.identifier.pmid22824866
dc.identifier.urihttps://depositonce.tu-berlin.de/handle/11303/5687
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-5307
dc.language.isoen
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.ddc540 Chemie und zugeordnete Wissenschaftende
dc.titleStructure of the catalytic sites in Fe/N/C-catalysts for O-2-reduction in PEM fuel cellsen
dc.typeArticleen
dc.type.versionpublishedVersionen
dcterms.bibliographicCitation.doi10.1039/c2cp41957b
dcterms.bibliographicCitation.issue33
dcterms.bibliographicCitation.journaltitlePhysical chemistry, chemical physicsen
dcterms.bibliographicCitation.originalpublishernameRoyal Society of Chemistryde
dcterms.bibliographicCitation.originalpublisherplaceCambridgede
dcterms.bibliographicCitation.pageend11688
dcterms.bibliographicCitation.pagestart11673
dcterms.bibliographicCitation.volume14
tub.accessrights.dnbdomain
tub.affiliationFak. 6 Planen Bauen Umwelt::Inst. Angewandte Geowissenschaften::FG Mineralogiede
tub.affiliation.facultyFak. 6 Planen Bauen Umweltde
tub.affiliation.groupFG Mineralogiede
tub.affiliation.instituteInst. Angewandte Geowissenschaftende
tub.publisher.universityorinstitutionTechnische Universität Berlin

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