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Suche nach „[G.] [Wittstock]“ hat 9 Publikationen gefunden
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    MobilNachhaltigTC Plattling MoMo

    Zeitschriftenartikel

    E. dos Santos Sardinha, Michael Sternad, H. Wilkening, H. Martin, G. Wittstock

    Nascent SEI-Surface Films on Single Crystalline Silicon Investigated by Scanning Electrochemical Microscopy

    ACS Applied Energy Materials, vol. 2, no. 2, pp. 1388-1392

    2019

    DOI: 10.1021/acsaem.8b01967

    Abstract anzeigen

    Silicon is a promising high-capacity host material for negative electrodes in lithium-ion batteries with low potential for the lithiation/delithiation reaction that is outside the stability window of organic carbonate electrolytes. Thus, the use of such electrodes critically depends on the formation of a protective solid electrolyte interphase (SEI) from the decomposition products of electrolyte components. Due to the large volume change upon charging, exposure of the electrode material to the electrolyte must be expected, and facile reformation of SEI is a scope for improving the stabilities of such electrodes. Here, we report the formation of incipient SEI layers on monocrystalline silicon by in situ imaging of their passivating properties using scanning electrochemical microscopy after potentiodynamic charging to different final potentials. The images show a local initiation of the SEI growth at potentials of around 1.0 V vs Li/Li+ in 1 M LiClO4 in propylene carbonate.

    MobilNachhaltigTC Plattling MoMo

    Zeitschriftenartikel

    H. Bülter, Michael Sternad, Santos Sardinha, Eduardo dos, J. Witt, C. Dosche, M. Wilkening, G. Wittstock

    Investigation of the Electron Transfer at Si Electrodes: Impact and Removal of the Native SiO 2 Layer

    Journal of The Electrochemical Society, vol. 163, no. 3

    2016

    DOI: 10.1149/2.0731603jes

    Abstract anzeigen

    Silicon is considered as one of the promising alternatives to graphite as negative electrode material in lithium-ion batteries. The electron transfer at uncharged microstructured and planar Si was characterized using the feedback mode of scanning electrochemical microscopy (SECM) and 2,5-di-tert-butyl-1,4-dimethoxybenzene as redox mediator. Approach curves and images demonstrate that the electron transfer rate constants at pristine Si are relatively small due to the native SiO2 surface layer. In addition, the electron transfer rate constants show local variations because of the heterogeneous coverage of SiO2. The SiO2 layer is at least partially removed by mechanical contact and abrasion with the microelectrode probe. After SiO2 removal by the microelectrode or by a hydrofluoric acid dip, the electron transfer rate constants increase strongly and remain heterogeneous. Moreover, the surface of the Si electrodes is at least stable over hours after SiO2 removal. The consequences for investigating the formation of the solid electrolyte interphase (SEI) on Si are discussed.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    H. Bülter, G. Denuault, Stefan Mátéfi-Tempfli, M. Mátéfi-Tempfli, C. Dosche, G. Wittstock

    Electrochemical analysis of nanostructured iron oxides using cyclic voltammetry and scanning electrochemical microscopy

    Electrochimica Acta, vol. 222, pp. 1326-1334

    2016

    Abstract anzeigen

    Iron oxides in general and especially hematite, α-Fe2O3, have become promising materials for the alkaline water electrolysis and photoelectrochemical water splitting, respectively. In the present study electrocatalytic electrodes with a thin film of α-Fe2O3 and with vertically aligned α-Fe2O3 nanowires were prepared. Cyclic voltammograms of the α-Fe2O3 nanowires revealed differences including a series of three unreported cathodic signals when compared to previously published voltammograms for polycrystalline iron oxides. The generation-collection mode of scanning electrochemical microscopy (SECM) using nanostructured Pt microdisc probes was exploited to detect soluble reaction products formed at the voltammetric peaks of the α-Fe2O3 electrode. SECM tip-substrate voltammetry unexpectedly showed that the reduction of FeVI to FeIII on the cathodic sweep is accompanied by significant O2 evolution.

    MobilNachhaltigTC Plattling MoMo

    Zeitschriftenartikel

    H. Bülter, Michael Sternad, M. Wilkening, G. Wittstock

    Impact of the Native SiO2 Surface Layer on the Electron Transfer at Amorphous Si Electrodes

    ECS Transactions (The Electrochemical Society), vol. 68, no. 2, pp. 1-11

    2015

    DOI: 10.1149/06802.0001ecst

    Abstract anzeigen

    The electron transfer at uncharged microstructured and planar amorphous (a-)Si was characterized using the feedback mode of scanning electrochemical microscopy (SECM) and 2,5-di-tert-butyl-1,4-dimethoxybenzene as redox mediator in carbonate electrolytes. Approach curves and images demonstrate that the electron transfer rate at pristine a-Si is relatively small due to the native SiO2 surface layer. In addition, the electron transfer rates show local variations because of the heterogeneous coverage of SiO2. After removal of the SiO2 layer, the effect of the solid electrolyte interphase (SEI) on electron transport rate can be studied. The SiO2 layer is at least partially removed by approach curve contact and scratching with the microelectrode probe. After SiO2 removal, the electron transfer rates increase strongly and remain heterogeneous.

    MobilNachhaltigTC Plattling MoMo

    Vortrag

    H. Bülter, Michael Sternad, M. Wilkening, G. Wittstock

    Comparison of Spatiotemperoal Changes of SEI Properies on Different Anodes by SECM

    ECS Conference on Electrochemical Energy Conversion & Storage with SOFC-XIV, Glasgow, United Kingdom

    2015

    NachhaltigEuropan Campus Rottal-Inn

    Vortrag

    G. Wittstock, G. Denuault, Stefan Mátéfi-Tempfli, H. Bülter, M. Mátéfi-Tempfli, A. Lesch, I. Schmidt, C. Dosche, M. Ahlf, K. Al-Shamery, A. Fanget, L. Forró

    Oxygen evolution at vertically aligned core-shell iron-iron oxide nanowire arrays

    24th ECS Meeting: Photoelectrochemistry and Photoassisted Electrocatalysis, San Francisco, CA, USA

    2013

    NachhaltigEuropan Campus Rottal-Inn

    Vortrag

    H. Bülter, G. Wittstock, Stefan Mátéfi-Tempfli, M. Mátéfi-Tempfli, G. Denuault

    Scanning electrochemical microscopy : Investigation of oxygen evolution from nanostructured iron oxide films and nanowires.

    Electrochemistry 2012: Fundamental and Engineering Needs for Sustainable Development, München

    2012

    NachhaltigEuropan Campus Rottal-Inn

    Vortrag

    H. Bülter, G. Wittstock, Stefan Mátéfi-Tempfli, M. Mátéfi-Tempfli, G. Denuault

    Scanning electrochemical microscopy: Investigation of oxygen evolution from nanostructured iron oxide films and nanowires

    12th International Fischer Symposium "Frontiers in Nanoelectrochemistry", Lübeck

    2012

    NachhaltigEuropan Campus Rottal-Inn

    Vortrag

    H. Bülter, G. Wittstock, Stefan Mátéfi-Tempfli, M. Mátéfi-Tempfli, G. Denuault

    Scanning electrochemical microscopy : Investigation of oxygen evolution from nanostructured iron oxide fims and nanowires

    23rd Lecture Conference on Photochemistry, Potsdam

    2012