Risch, Marcel

[["dc.bibliographiccitation.firstpage","1266"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Journal of Synchrotron Radiation"],["dc.bibliographiccitation.lastpage","1271"],["dc.bibliographiccitation.volume","26"],["dc.contributor.author","Döring, Florian"],["dc.contributor.author","Risch, Marcel"],["dc.contributor.author","Rösner, Benedikt"],["dc.contributor.author","Beye, Martin"],["dc.contributor.author","Busse, Philipp"],["dc.contributor.author","Kubiček, Katharina"],["dc.contributor.author","Glaser, Leif"],["dc.contributor.author","Miedema, Piter S."],["dc.contributor.author","Soltau, Jakob"],["dc.contributor.author","Raiser, Dirk"],["dc.contributor.author","Guzenko, Vitaliy A."],["dc.contributor.author","Szabadics, Lukas"],["dc.contributor.author","Kochanneck, Leif"],["dc.contributor.author","Baumung, Max"],["dc.contributor.author","Buck, Jens"],["dc.contributor.author","Jooss, Christian"],["dc.contributor.author","Techert, Simone"],["dc.contributor.author","David, Christian"],["dc.date.accessioned","2020-12-10T18:25:59Z"],["dc.date.available","2020-12-10T18:25:59Z"],["dc.date.issued","2019"],["dc.description.abstract","X-ray absorption spectroscopy (XAS) is a powerful element-specific technique that allows the study of structural and chemical properties of matter. Often an indirect method is used to access the X-ray absorption (XA). This work demonstrates a new XAS implementation that is based on off-axis transmission Fresnel zone plates to obtain the XA spectrum of La0.6Sr0.4MnO3 by analysis of three emission lines simultaneously at the detector, namely the O 2p-1s, Mn 3s-2p and Mn 3d-2p transitions. This scheme allows the simultaneous measurement of an integrated total fluorescence yield and the partial fluorescence yields (PFY) of the Mn 3s-2p and Mn 3d-2p transitions when scanning the Mn L-edge. In addition to this, the reduction in O fluorescence provides another measure for absorption often referred to as the inverse partial fluorescence yield (IPFY). Among these different methods to measure XA, the Mn 3s PFY and IPFY deviate the least from the true XA spectra due to the negligible influence of selection rules on the decay channel. Other advantages of this new scheme are the potential to strongly increase the efficiency and throughput compared with similar measurements using conventional gratings and to increase the signal-to-noise of the XA spectra as compared with a photodiode. The ability to record undistorted bulk XA spectra at high flux is crucial for future in situ spectroscopy experiments on complex materials."],["dc.identifier.doi","10.1107/S1600577519003898"],["dc.identifier.issn","1600-5775"],["dc.identifier.pmid","31274453"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16305"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/75901"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.relation","SFB 1073: Kontrolle von Energiewandlung auf atomaren Skalen"],["dc.relation","SFB 1073 | Topical Area C | C02 In situ hochauflösende Untersuchung des aktiven Zustands bei der photo- und elektrochemischen Wasserspaltung"],["dc.relation","SFB 1073 | Topical Area C | C05 Kontrolle Elektronen-getriebener Chemie durch Interkalation"],["dc.relation.eissn","1600-5775"],["dc.relation.issn","1600-5775"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.relation.workinggroup","RG Techert (Structural Dynamics in Chemical Systems)"],["dc.title","A zone-plate-based two-color spectrometer for indirect X-ray absorption spectroscopy"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2218"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Sustainable Energy & Fuels"],["dc.bibliographiccitation.lastpage","2226"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Baumung, Max"],["dc.contributor.author","Schönewald, Florian"],["dc.contributor.author","Erichsen, Torben"],["dc.contributor.author","Volkert, Cynthia A."],["dc.contributor.author","Risch, Marcel"],["dc.date.accessioned","2021-10-15T08:51:41Z"],["dc.date.available","2021-10-15T08:51:41Z"],["dc.date.issued","2019"],["dc.description.abstract","We investigate LiMn2O4 as a model catalyst for the oxygen evolution reaction (OER), because it shares the cubane structure with the active site of photosystem II. Specifically, we study the influence of different particle sizes of LiMn2O4 on the OER in a sodium hydroxide electrolyte. The product currents of manganese corrosion and oxygen evolution were obtained by rotating ring disk electrodes (RRDE). Physical characterization by various methods supports identical surface chemistry and microstructure of the pristine powders. We obtained similar oxygen current densities of 40(14) μA cmECSA−2 and 26(5) μA cmECSA−2 for micro- and nano-sized particles at 1.68 V vs. RHE. However, the total current densities differed drastically and while the micro-powder had a high disk current density of 205(2) μA cmECSA−2, its faradaic efficiency was only 25%. In contrast, the faradaic efficiency of the nanopowder was at least 75%. We hypothesize that a Mn redox process may occur in the bulk in parallel and possibly in combination with oxygen evolution on the surface based on the observed difference between the total and product current densities. Knowledge of the product currents is crucial for distinguishing the mechanisms of corrosion and catalysis and for designing better catalysts with high faradaic efficiency."],["dc.identifier.doi","10.1039/C8SE00551F"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16500"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/90942"],["dc.identifier.url","https://publications.goettingen-research-online.de/handle/2/62345"],["dc.language.iso","en"],["dc.relation","SFB 1073: Kontrolle von Energiewandlung auf atomaren Skalen"],["dc.relation","SFB 1073 | Topical Area C | C05 Kontrolle Elektronen-getriebener Chemie durch Interkalation"],["dc.relation.issn","2398-4902"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.rights","CC BY 3.0"],["dc.title","Influence of particle size on the apparent electrocatalytic activity of LiMn2O4 for oxygen evolution"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.issue","20"],["dc.bibliographiccitation.journal","ChemPhysChem"],["dc.bibliographiccitation.lastpage","9"],["dc.bibliographiccitation.volume","20"],["dc.contributor.author","Baumung, Max"],["dc.contributor.author","Kollenbach, Leon"],["dc.contributor.author","Xi, Lifei"],["dc.contributor.author","Risch, Marcel"],["dc.date.accessioned","2019-11-11T13:15:13Z"],["dc.date.accessioned","2021-10-11T11:33:49Z"],["dc.date.available","2019-11-11T13:15:13Z"],["dc.date.available","2021-10-11T11:33:49Z"],["dc.date.issued","2019"],["dc.description.abstract","Chemical and structural changes preceding electrocatalysis obfuscate the nature of the active state of electrocatalysts for the oxygen evolution reaction (OER), which calls for model systems to gain systematic insight. We investigated the effect of bulk oxidation on the overpotential of ink-casted LiMn2 O4 electrodes by a rotating ring-disk electrode (RRDE) setup and X-ray absorption spectroscopy (XAS) at the K shell core level of manganese ions (Mn-K edge). The cyclic voltammogram of the RRDE disk shows pronounced redox peaks in lithium hydroxide electrolytes with pH between 12 and 13.5, which we assign to bulk manganese redox based on XAS. The onset of the OER is pH-dependent on the scale of the reversible hydrogen electrode (RHE) with a Nernst slope of -40(4) mV/pH at -5 μA monitored at the RRDE ring. To connect this trend to catalyst changes, we develop a simple model for delithiation of LiMn2 O4 in LiOH electrolytes, which gives the same Nernst slope of delithiation as our experimental data, i. e., 116(25) mV/pH. From this data, we construct an ERHE -pH diagram that illustrates robustness of LiMn2 O4 against oxidation above pH 13.5 as also verified by XAS. We conclude that manganese oxidation is the origin of the increase of the OER overpotential at pH lower than 14 and also of the pH dependence on the RHE scale. Our work highlights that vulnerability to transition metal redox may lead to increased overpotentials, which is important for the design of stable electrocatalysts."],["dc.description.sponsorship","collaborative research center (CRC)"],["dc.description.sponsorship","HZB http://dx.doi.org/10.13039/100013110"],["dc.identifier.doi","10.1002/cphc.201900601"],["dc.identifier.eissn","1439-7641"],["dc.identifier.isbn","31359564"],["dc.identifier.issn","1439-4235"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16655"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/90626"],["dc.language.iso","en"],["dc.notes.intern","Migrated from goescholar"],["dc.relation","SFB 1073: Kontrolle von Energiewandlung auf atomaren Skalen"],["dc.relation","SFB 1073 | Topical Area C | C05 Kontrolle Elektronen-getriebener Chemie durch Interkalation"],["dc.relation.eissn","1439-7641"],["dc.relation.issn","1439-7641"],["dc.relation.issn","1439-4235"],["dc.relation.orgunit","Fakultät für Physik"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.rights","CC BY 3.0"],["dc.rights.access","openAccess"],["dc.rights.uri","https://creativecommons.org/licenses/by/3.0/"],["dc.subject","X-ray absorption spectroscopy; aqueous battery; electrocatalysis; oxygen evolution reaction; pH dependence"],["dc.subject.ddc","530"],["dc.title","Undesired Bulk Oxidation of LiMn2O4 Increases Overpotential of Electrocatalytic Water Oxidation in Lithium Hydroxide Electrolytes"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]