Cyanamide route to calcium-manganese oxide foams for water oxidation

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dc.contributor.authorBaktash, Elham
dc.contributor.authorZaharieva, Ivelina
dc.contributor.authorSchröder, Marc
dc.contributor.authorGoebel, Caren
dc.contributor.authorDau, Holger
dc.contributor.authorThomas, Arne
dc.date.accessioned2016-06-24T05:35:12Z
dc.date.available2016-06-24T05:35:12Z
dc.date.issued2013
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.abstractIn nature, photosynthetic water oxidation is efficiently catalysed at a protein-bound μ-oxido Mn4Ca cluster. This cluster consists of earth abundant, non-toxic elements and serves as a paragon for development of synthetic catalysts. In this study we developed porous calcium–manganese oxides with a unique foam-like nanostructure prepared via a facile and robust synthetic route using cyanamide as a porogen. A series of such oxide foams annealed at different temperatures was characterized by TEM, SEM, XRD, N2 physisorption, and X-ray absorption spectroscopy (XAS) in order to correlate crystallinity, atomic structure, surface area and oxidation state of the materials with catalytic activity. Some of the resulting Ca–Mn oxides show high activity as catalysts for water oxidation in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. An amorphous calcium–manganese-oxide foam with 130 m2 g−1 surface area and Mn oxidation state of +3.6 was identified to be most active; its activity is superior to previously reported Ca–Mn oxides. At the atomic level, this material shares structural motifs with the biological paragon as revealed by dual-edge XAS at the Mn and Ca K-edge. Rather than nanostructure and surface area, the atomic structure of the Ca–Mn oxide and the extent of structural order appear to be crucial determinants of catalytic activity. Fully disordered low-valent Mn materials as well as high-valent but crystalline Mn–Ca oxides are unreactive. Highly disordered variants of layered manganese oxide with Ca and water molecules interfacing layer fragments are most reactive.en
dc.description.sponsorshipDFG, EXC 314, Unifying Concepts in Catalysisen
dc.identifier.eissn1477-9226
dc.identifier.pmid24091767
dc.identifier.urihttps://depositonce.tu-berlin.de/handle/11303/5637
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-5257
dc.language.isoen
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.ddc540 Chemie und zugeordnete Wissenschaftende
dc.titleCyanamide route to calcium-manganese oxide foams for water oxidationen
dc.typeArticleen
dc.type.versionpublishedVersionen
dcterms.bibliographicCitation.doi10.1039/c3dt51693h
dcterms.bibliographicCitation.issue48
dcterms.bibliographicCitation.journaltitleDalton transactions : a journal of inorganic chemistry, including bioinorganic, organometallic, and solid-state chemistryen
dcterms.bibliographicCitation.originalpublishernameRoyal Society of Chemistryde
dcterms.bibliographicCitation.originalpublisherplaceCambridgede
dcterms.bibliographicCitation.pageend16929
dcterms.bibliographicCitation.pagestart16920
dcterms.bibliographicCitation.volume42
tub.accessrights.dnbdomain
tub.affiliationFak. 2 Mathematik und Naturwissenschaften::Inst. Chemiede
tub.affiliation.facultyFak. 2 Mathematik und Naturwissenschaftende
tub.affiliation.instituteInst. Chemiede
tub.publisher.universityorinstitutionTechnische Universität Berlin

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