dc.contributor.author
Riedel, Wiebke
dc.contributor.author
Thum, Lukas
dc.contributor.author
Möser, Jannik
dc.contributor.author
Fleischer, Vinzenz
dc.contributor.author
Simon, Ulla
dc.contributor.author
Siemensmeyer, Konrad
dc.contributor.author
Schnegg, Alexander
dc.contributor.author
Schomäcker, Reinhard
dc.contributor.author
Risse, Thomas
dc.contributor.author
Dinse, Klaus-Peter
dc.date.accessioned
2020-04-07T13:35:57Z
dc.date.available
2020-04-07T13:35:57Z
dc.identifier.uri
https://refubium.fu-berlin.de/handle/fub188/27078
dc.identifier.uri
http://dx.doi.org/10.17169/refubium-26839
dc.description.abstract
The magnetic properties of Mn–Na2WO4/SiO2, a promising catalyst for the oxidative coupling of methane (OCM), were investigated in two states: reduced with CH4 until reactivity ceased and reoxidized with O2 to probe for state-specific magnetic species and their involvement in the oxygen storage of the catalyst. Employing temperature- and frequency-dependent continuous-wave (cw) and pulsed electron paramagnetic resonance (EPR) spectroscopy combined with SQUID (Superconducting Quantum Interference Device) magnetization measurements allowed us to identify a variety of Mn species in different oxidation states and their role in the oxygen storage capability of the catalyst. For the reoxidized catalyst, the formation of magnetically ordered Mn(II)- and Mn(III)-containing Mn3O4 as well as Mn2O3 or MnMn6SiO12 phases were detected. The reduced catalyst exhibits almost ideal paramagnetic behavior and a strong, broad cw EPR signal consistent with the formation of short-range ordered nanosized Mn(II) oxide, demonstrating the involvement of these Mn species in the oxygen storage capability of the catalyst. In contrast, rather isolated, highly oxidized Mn(IV) as well as different Mn(III) species were observed by pulsed EPR, which are not affected by the oxidation state of the Mn–Na2WO4/SiO2 catalyst, suggesting an inaccessible, buried location, presumably in the SiO2 support. Furthermore, paramagnetic sites with an effective S = 1/2 spin are detected, whose intensity depends on the oxidation state of the sample and are thus involved in the oxygen storage capacity of the catalyst.
en
dc.format.extent
31 Seiten
dc.rights.uri
http://www.fu-berlin.de/sites/refubium/rechtliches/Nutzungsbedingungen
dc.subject
magnetic properties
en
dc.subject
Electron paramagnetic resonance spectroscopy
en
dc.subject
transition metals
en
dc.subject
phase transitions
en
dc.subject.ddc
500 Naturwissenschaften und Mathematik::530 Physik::530 Physik
dc.title
Magnetic properties of reduced and reoxidized Mn–Na2WO4/SiO2: A catalyst for oxidative coupling of methane (OCM)
dc.type
Wissenschaftlicher Artikel
dcterms.bibliographicCitation.doi
10.1021/acs.jpcc.8b07386
dcterms.bibliographicCitation.journaltitle
The journal of physical chemistry
dcterms.bibliographicCitation.number
39
dcterms.bibliographicCitation.pagestart
22605
dcterms.bibliographicCitation.pageend
22614
dcterms.bibliographicCitation.volume
122
dcterms.bibliographicCitation.url
https://doi.org/10.1021/acs.jpcc.8b07386
refubium.affiliation
Physik
refubium.note.author
This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.jpcc.8b07386.
refubium.resourceType.isindependentpub
no
dcterms.accessRights.openaire
open access
dcterms.isPartOf.issn
1932-7447
dcterms.isPartOf.eissn
1932-7455