Publications by authors named "Michaela Kogler"

14 Publications

  • Page 1 of 1

Degradation of synthetic and wood-based cellulose fabrics in the marine environment: Comparative assessment of field, aquarium, and bioreactor experiments.

Sci Total Environ 2021 May 27;791:148060. Epub 2021 May 27.

Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA. Electronic address:

As global production of textiles rapidly grows, there is urgency to understand the persistence of fabrics in the marine environment, particularly from the microfibers they shed during wearing and washing. Here, we show that fabrics containing polyester (one of the most common plastics) remained relatively intact (viz., with a limited biofilm) after >200 days in seawater off the Scripps Oceanography pier (La Jolla, CA), in contrast to wood-based cellulose fabrics that fell apart within 30 days. We also show similar results under experimental aquaria (in open circuit with the pier waters) as well as bioreactor settings (in close circuit, using microbial inoculum from the North Sea, off Belgium), using nonwoven fabrics and individual fibers, respectively. The fact that fibers released from synthetic textiles remain persistent and non-biodegradable despite their small (invisible) size, highlights concern for the growing industry that uses polyester from recycled plastics to make clothing.
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http://dx.doi.org/10.1016/j.scitotenv.2021.148060DOI Listing
May 2021

LiCoTeO: synthesis, single-crystal structure and physical properties of a new tellurate compound with Co/Co mixed valence and orthogonally oriented Li-ion channels.

Dalton Trans 2017 Sep;46(37):12663-12674

Institut für Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria.

A tellurate compound with Co/Co mixed valence states and lithium ions within orthogonally oriented channels was realized in LiCoTeO. The single-crystal structure determination revealed two independent and interpenetrating Li/O and (Co,Te)/O substructures with octahedral oxygen coordination of the metal atoms. In contrast to other mixed oxides, a honeycomb-like ordering of CoO and TeO octahedra was not observed. LiCoTeO crystallizes orthorhombically with the following unit cell parameters and refinement results: Fddd, a = 588.6(2), b = 856.7(2), c = 1781.5(4) pm, R = 0.0174, wR = 0.0462, 608 F values, and 33 variables. Additional electron density in tetrahedral voids in combination with neighboring face-linked and under-occupied octahedral lithium sites offers an excellent possible diffusion pathway for lithium ions. According to the symmetry of the crystal structure the diffusion pathways in LiCoTeO were found in two orthogonal orientations. The Co/Co mixed valence was investigated via X-ray photoelectron spectroscopy (XPS), revealing a composition comparable to that derived from single-crystal X-ray diffractometry. Magnetic susceptibility measurements underlined the coexistence of Co and Co, the title compound, however, showed no magnetic ordering down to low temperatures. The ionic conductivity of LiCoTeO was determined via alternating current (AC) electrochemical impedance spectroscopy and was found to be in the range of 1.6 × 10 S cm at 573 K.
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http://dx.doi.org/10.1039/c7dt02663cDOI Listing
September 2017

Surface chemistry and stability of metastable corundum-type InO.

Phys Chem Chem Phys 2017 Jul;19(29):19407-19419

Institut für Physikalische Chemie, Universität Innsbruck, Innrain 52c, A-6020 Innsbruck, Austria.

To account for the explanation of an eventual sensing and catalytic behavior of rhombohedral InO (rh-InO) and the dependence of the metastability of the latter on gas atmospheres, in situ electrochemical impedance spectroscopic (EIS), Fourier-transform infrared spectroscopic (FT-IR), in situ X-ray diffraction and in situ thermogravimetric analyses in inert (helium) and reactive gases (hydrogen, carbon monoxide and carbon dioxide) have been conducted to link the gas-dependent electrical conductivity features and the surface chemical properties to its metastability towards cubic InO. In particular, for highly reducible oxides such as InO, for which not only the formation of oxygen vacancies, but deep reduction to the metallic state (i.e. metallic indium) also has to be taken into account, this approach is imperative. Temperature-dependent impedance features are strongly dependent on the respective gas composition and are assigned to distinct changes in either surface adsorbates or free charge carrier absorbance, allowing for differentiating and distinguishing between bulk reduction-related features from those directly arising from surface chemical alterations. For the measurements in an inert gas atmosphere, this analysis specifically also included monitoring the fate of differently bonded, and hence, differently reactive, hydroxyl groups. Reduction of rh-InO proceeds to a large extent indirectly via rh-InO → c-InO → In metal. As deduced from the CO and CO adsorption experiments, rhombohedral InO exhibits predominantly Lewis acidic surface sites. The basic character is less pronounced, directly explaining the previously observed high (inverse) water-gas shift activity and the low CO selectivity in methanol steam reforming.
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http://dx.doi.org/10.1039/c7cp03632aDOI Listing
July 2017

Surface chemistry of pure tetragonal ZrO and gas-phase dependence of the tetragonal-to-monoclinic ZrO transformation.

Dalton Trans 2017 Apr;46(14):4554-4570

Institute of Physical Chemistry, University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria.

The surface chemical properties of undoped tetragonal ZrO and the gas-phase dependence of the tetragonal-to-monoclinic transformation are studied using a tetragonal ZrO polymorph synthesized via a sol-gel method from an alkoxide precursor. The obtained phase-pure tetragonal ZrO is defective and strongly hydroxylated with pronounced Lewis acidic and Brønsted basic surface sites. Combined in situ FT-infrared and electrochemical impedance measurements reveal effective blocking of coordinatively unsaturated sites by both CO and CO, as well as low conductivity. The transformation into monoclinic ZrO is suppressed up to temperatures of ∼723 K independent of the gas phase composition, in contrast to at higher temperatures. In inert atmospheres, the persisting structural defectivity leads to a high stability of tetragonal ZrO, even after a heating-cooling cycle up to 1273 K. Treatments in CO and H increase the amount of monoclinic ZrO upon cooling (>85 wt%) and the associated formation of either Zr-surface-(oxy-)carbide or dissolved hydrogen. The transformation is strongly affected by the sintering/pressing history of the sample, due to significant agglomeration of small crystals on the surface of sintered pellets. Two factors dominate the properties of tetragonal ZrO: defect chemistry and hydroxylation degree. In particular, moist conditions promote the phase transformation, although at significantly higher temperatures as previously reported for doped tetragonal ZrO.
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http://dx.doi.org/10.1039/c6dt04847aDOI Listing
April 2017

Evidence for dissolved hydrogen in the mixed ionic-electronic conducting perovskites LaSrFeO and SrTiFeO.

Phys Chem Chem Phys 2016 Sep;18(38):26873-26884

Institute of Physical Chemistry, University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria.

Two mixed ionic-electronic conducting, Fe-containing perovskites were investigated regarding their reducibility in dry H, namely lanthanum strontium ferrite (LSF4, LaSrFeO) and strontium titanium ferrite (STF3, SrTiFeO). Upon treatment under comparable reduction conditions, LSF4 is by far more affected by reduction and is reduced more deeply than STF3. Thermal treatments of fully oxidized or slightly reduced LSF4/STF3 at decreased O partial pressure lead to spontaneous desorption of O. Temperature-programmed desorption (TPD) spectra of H reveal distinct differences in H and HO desorption. A simple mass balance of H reveals that oxygen vacancies formed on STF3 are more resilient towards O re-oxidation compared to those on LSF4. The results also imply that substantial amounts of hydrogen are dissolved in the bulk of LSF4 or STF3. 4.9 × 10 mol H per mol LSF4 and 1.6 × 10 mol H per mol STF3 are incorporated if the specimens are heated in flowing/dry H up to 550 °C and 612 °C, respectively. For LSF4 this equals about 13 hypothetical ML of H and for STF3 about 20 hypothetical ML of H. This conclusion is also supported by Fourier-transform infrared spectroscopy (FT-IR). FT-IR reveals water formation during static H treatment of LSF4/STF3, which indicates perovskite reduction. Furthermore, both samples behave extraordinarily hydrophobic and no chemistry involving surface hydroxy groups was observed.
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http://dx.doi.org/10.1039/c6cp05392kDOI Listing
September 2016

Structural and Electrochemical Properties of Physisorbed and Chemisorbed Water Layers on the Ceramic Oxides Y2O3, YSZ, and ZrO2.

ACS Appl Mater Interfaces 2016 Jun 15;8(25):16428-43. Epub 2016 Jun 15.

Institute of Physical Chemistry, University of Innsbruck , Innrain 80-82, A-6020 Innsbruck, Austria.

A combination of operando Fourier transform infrared spectroscopy, operando electrochemical-impedance spectroscopy, and moisture-sorption measurements has been exploited to study the adsorption and conduction behavior of H2O and D2O on the technologically important ceramic oxides YSZ (8 mol % Y2O3), ZrO2, and Y2O3. Because the characterization of the chemisorbed and physisorbed water layers is imperative to a full understanding of (electro-)catalytically active doped oxide surfaces and their application in technology, the presented data provide the specific reactivity of these oxides toward water over a pressure-and-temperature parameter range extending up to, e.g., solid-oxide fuel cell (SOFC)-relevant conditions. The characteristic changes of the related infrared bands could directly be linked to the associated conductivity and moisture-sorption data. For YSZ, a sequential dissociative water ("ice-like" layer) and polymeric chained water ("liquid-like") water-adsorption model for isothermal and isobaric conditions over a pressure range of 10(-5) to 24 mbar and a temperature range from room temperature up to 1173 K could be experimentally verified. On pure monoclinic ZrO2, in contrast to highly hydroxylated YSZ and Y2O3, a high surface concentration of OH groups from water chemisorption is absent at any temperature and pressure. Thus, the ice-like and following molecular water layers exhibit no measurable protonic conduction. We show that the water layers, even under these rather extreme experimental conditions, play a key role in understanding the function of these materials. Furthermore, the reported data are supposed to provide an extended basis for the further investigation of close-to-real gas adsorption or catalyzed heterogeneous reactions.
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http://dx.doi.org/10.1021/acsami.6b03566DOI Listing
June 2016

Structural and chemical degradation mechanisms of pure YSZ and its components ZrO2 and Y2O3 in carbon-rich fuel gases.

Phys Chem Chem Phys 2016 05;18(21):14333-49

Institute of Physical Chemistry, University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria.

Structural and chemical degradation mechanisms of metal-free yttria stabilized zirconia (YSZ-8, 8 mol% Y2O3 in ZrO2) in comparison to its pure oxidic components ZrO2 and Y2O3 have been studied in carbon-rich fuel gases with respect to coking/graphitization and (oxy)carbide formation. By combining operando electrochemical impedance spectroscopy (EIS), operando Fourier-transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), the removal and suppression of CH4- and CO-induced carbon deposits and of those generated in more realistic fuel gas mixtures (syngas, mixtures of CH4 or CO with CO2 and H2O) was examined under SOFC-relevant conditions up to 1273 K and ambient pressures. Surface-near carbidization is a major problem already on the "isolated" (i.e. Nickel-free) cermet components, leading to irreversible changes of the conduction properties. Graphitic carbon deposition takes place already on the "isolated" oxides under sufficiently fuel-rich conditions, most pronounced in the pure gases CH4 and CO, but also significantly in fuel gas mixtures containing H2O and CO2. For YSZ, a comparative quantification of the total amount of deposited carbon in all gases and mixtures is provided and thus yields favorable and detrimental experimental approaches to suppress the carbon formation. In addition, the effectivity and reversibility of removal of the coke/graphite layers was comparably studied in the pure oxidants O2, CO2 and H2O and their effective contribution upon addition to the pure fuel gases CO and CH4 verified.
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http://dx.doi.org/10.1039/c6cp02458kDOI Listing
May 2016

High-Temperature Carbon Deposition on Oxide Surfaces by CO Disproportionation.

J Phys Chem C Nanomater Interfaces 2016 Jan 7;120(3):1795-1807. Epub 2016 Jan 7.

Institute of Physical Chemistry and Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck , Innrain 80-82, A-6020 Innsbruck, Austria.

Carbon deposition due to the inverse Boudouard reaction (2CO → CO + C) has been studied on yttria-stabilized zirconia (YSZ), YO, and ZrO in comparison to CH by a variety of different chemical, structural, and spectroscopic characterization techniques, including electrochemical impedance spectroscopy (EIS), Fourier-transform infrared (FT-IR) spectroscopy and imaging, Raman spectroscopy, and electron microscopy. Consentaneously, all experimental methods prove the formation of a more or less conducting carbon layer (depending on the used oxide) of disordered nanocrystalline graphite covering the individual grains of the respective pure oxides after treatment in flowing CO at temperatures above ∼1023 K. All measurements show that during carbon deposition, a more or less substantial surface reduction of the oxides takes place. These results, therefore, reveal that the studied pure oxides can act as efficient nonmetallic substrates for CO-induced growth of highly distorted graphitic carbon with possible important technological implications especially with respect to treatment in pure CO or CO-rich syngas mixtures. Compared to CH, more carbon is generally deposited in CO under otherwise similar experimental conditions. Although Raman and electron microscopy measurements do not show substantial differences in the structure of the deposited carbon layers, in particular, electrochemical impedance measurements reveal major differences in the dynamic growth process of the carbon layer, eventually leading to less percolated islands and suppressed metallic conductivity in comparison to CH-induced graphite.
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http://dx.doi.org/10.1021/acs.jpcc.5b12210DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4735807PMC
January 2016

Enhanced kinetic stability of pure and Y-doped tetragonal ZrO2.

Inorg Chem 2014 Dec 4;53(24):13247-57. Epub 2014 Dec 4.

Institute of Physical Chemistry, ‡Institute of Inorganic and Theoretical Chemistry, and §Institute of Mineralogy and Petrography, University of Innsbruck , A-6020 Innsbruck, Austria.

The kinetic stability of pure and yttrium-doped tetragonal zirconia (ZrO2) polymorphs prepared via a pathway involving decomposition of pure zirconium and zirconium + yttrium isopropoxide is reported. Following this preparation routine, high surface area, pure, and structurally stable polymorphic modifications of pure and Y-doped tetragonal zirconia are obtained in a fast and reproducible way. Combined analytical high-resolution in situ transmission electron microscopy, high-temperature X-ray diffraction, and chemical and thermogravimetric analyses reveals that the thermal stability of the pure tetragonal ZrO2 structure is very much dominated by kinetic effects. Tetragonal ZrO2 crystallizes at 400 °C from an amorphous ZrO2 precursor state and persists in the further substantial transformation into the thermodynamically more stable monoclinic modification at higher temperatures at fast heating rates. Lower heating rates favor the formation of an increasing amount of monoclinic phase in the product mixture, especially in the temperature region near 600 °C and during/after recooling. If the heat treatment is restricted to 400 °C even under moist conditions, the tetragonal phase is permanently stable, regardless of the heating or cooling rate and, as such, can be used as pure catalyst support. In contrast, the corresponding Y-doped tetragonal ZrO2 phase retains its structure independent of the heating or cooling rate or reaction environment. Pure tetragonal ZrO2 can now be obtained in a structurally stable form, allowing its structural, chemical, or catalytic characterization without in-parallel triggering of unwanted phase transformations, at least if the annealing or reaction temperature is restricted to T ≤ 400 °C.
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http://dx.doi.org/10.1021/ic502623tDOI Listing
December 2014

A high-temperature, ambient-pressure ultra-dry operando reactor cell for Fourier-transform infrared spectroscopy.

Rev Sci Instrum 2014 Aug;85(8):084102

Institute of Physical Chemistry, University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria.

The construction of a newly designed high-temperature, high-pressure FT-IR reaction cell for ultra-dry in situ and operando operation is reported. The reaction cell itself as well as the sample holder is fully made of quartz glass, with no hot metal or ceramic parts in the vicinity of the high-temperature zone. Special emphasis was put on chemically absolute water-free and inert experimental conditions, which includes reaction cell and gas-feeding lines. Operation and spectroscopy up to 1273 K is possible, as well as pressures up to ambient conditions. The reaction cell exhibits a very easy and variable construction and can be adjusted to any available FT-IR spectrometer. Its particular strength lies in its possibility to access and study samples under very demanding experimental conditions. This includes studies at very high temperatures, e.g., for solid-oxide fuel cell research or studies where the water content of the reaction mixtures must be exactly adjusted. The latter includes all adsorption studies on oxide surfaces, where the hydroxylation degree is of paramount importance. The capability of the reaction cell will be demonstrated for two selected examples where information and in due course a correlation to other methods can only be achieved using the presented setup.
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http://dx.doi.org/10.1063/1.4891630DOI Listing
August 2014

Hydrogen Surface Reactions and Adsorption Studied on YO, YSZ, and ZrO

J Phys Chem C Nanomater Interfaces 2014 Apr 2;118(16):8435-8444. Epub 2014 Apr 2.

Institute of Physical Chemistry, University of Innsbruck , Innrain 52a, A-6020 Innsbruck, Austria.

The surface reactivity of YO, YSZ, and ZrO polycrystalline powder samples toward H has been comparatively studied by a pool of complementary experimental techniques, comprising volumetric methods (temperature-programmed volumetric adsorption/oxidation and thermal desorption spectrometry), spectroscopic techniques (in situ electric impedance and in situ Fourier-transform infrared spectroscopy), and eventually structural characterization methods (X-ray diffraction and scanning electron microscopy). Reduction has been observed on all three oxides to most likely follow a surface or near-surface-limited mechanism involving removal of surface OH-groups and associated formation of water without formation of a significant number of anionic oxygen vacancies. Partly reversible adsorption of H was proven on the basis of molecular H desorption. Dictated by the specific hydrophilicity of the oxide, readsorption of water eventually takes place. The inference of this surface-restricted mechanism is further corroborated by the fact that no bulk structural and/or morphological changes were observed upon reduction even at the highest reduction temperatures (1173 K). We anticipate relevant implications for the use of especially YSZ in fuel cell research, since in particular the chemical state and structure of the surface under typical reducing high-temperature conditions affects the operation of the entire cell.
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http://dx.doi.org/10.1021/jp5008472DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4001439PMC
April 2014

Methane Decomposition and Carbon Growth on YO, Yttria-Stabilized Zirconia, and ZrO

Chem Mater 2014 Feb 5;26(4):1690-1701. Epub 2014 Feb 5.

Institute of Physical Chemistry, University of Innsbruck , Innrain 52a, A-6020 Innsbruck, Austria.

Carbon deposition following thermal methane decomposition under dry and steam reforming conditions has been studied on yttria-stabilized zirconia (YSZ), YO, and ZrO by a range of different chemical, structural, and spectroscopic characterization techniques, including aberration-corrected electron microscopy, Raman spectroscopy, electric impedance spectroscopy, and volumetric adsorption techniques. Concordantly, all experimental techniques reveal the formation of a conducting layer of disordered nanocrystalline graphite covering the individual grains of the respective pure oxides after treatment in dry methane at temperatures ≥ 1000 K. In addition, treatment under moist methane conditions causes additional formation of carbon-nanotube-like architectures by partial detachment of the graphite layers. All experiments show that during carbon growth, no substantial reduction of any of the oxides takes place. Our results, therefore, indicate that these pure oxides can act as efficient nonmetallic substrates for methane-induced growth of different carbon species with potentially important implications regarding their use in solid oxide fuel cells. Moreover, by comparing the three oxides, we could elucidate differences in the methane reactivities of the respective SOFC-relevant purely oxidic surfaces under typical SOFC operation conditions without the presence of metallic constituents.
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http://dx.doi.org/10.1021/cm404062rDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3935620PMC
February 2014

In Situ FT-IR Spectroscopic Study of CO and CO Adsorption on YO, ZrO, and Yttria-Stabilized ZrO

J Phys Chem C Nanomater Interfaces 2013 Aug 2;117(34):17666-17673. Epub 2013 Aug 2.

Institute of Physical Chemistry, University of Innsbruck , Innrain 52a, A-6020 Innsbruck, Austria.

In situ FT-IR spectroscopy was exploited to study the adsorption of CO and CO on commercially available yttria-stabilized ZrO (8 mol % Y, YSZ-8), YO, and ZrO. All three oxides were pretreated at high temperatures (1173 K) in air, which leads to effective dehydroxylation of pure ZrO. Both YO and YSZ-8 show a much higher reactivity toward CO and CO adsorption than ZrO because of more facile rehydroxylation of Y-containing phases. Several different carbonate species have been observed following CO adsorption on YO and YSZ-8, which are much more strongly bound on the former, due to formation of higher-coordinated polydentate carbonate species upon annealing. As the crucial factor governing the formation of carbonates, the presence of reactive (basic) surface hydroxyl groups on Y-centers was identified. Therefore, chemisorption of CO most likely includes insertion of the CO molecule into a reactive surface hydroxyl group and the subsequent formation of a bicarbonate species. Formate formation following CO adsorption has been observed on all three oxides but is less pronounced on ZrO due to effective dehydroxylation of the surface during high-temperature treatment. The latter generally causes suppression of the surface reactivity of ZrO samples regarding reactions involving CO or CO as reaction intermediates.
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http://dx.doi.org/10.1021/jp405625xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3759166PMC
August 2013

Immunolocalization of BK channels in hippocampal pyramidal neurons.

Eur J Neurosci 2006 Jul;24(2):442-54

Department of Medical Genetics, Molecular and Clinical Pharmacology, Division for Molecular and Cellular Pharmacology, Medical University Innsbruck, Peter-Mayr Strasse 1, 6020 Innsbruck, Austria.

Neurons are highly specialized cells in which the integration and processing of electrical signals critically depends on the precise localization of ion channels. For large-conductance Ca(2+)- activated K(+) (BK) channels, targeting to presynaptic membranes in hippocampal pyramidal cells was reported; however, functional evidence also suggests a somatodendritic localization. Therefore we re-examined the subcellular distribution of BK channels in mouse hippocampus using a panel of independent antibodies in a combined approach of conventional immunocytochemistry on cultured neurons, pre- and postembedding electron microscopy and immunoprecipitation. In cultured murine hippocampal neurons, the colocalization of BK channels with both pre- and postsynaptic marker proteins was observed. Electron microscopy confirmed targeting of BK channels to axonal as well as dendritic membranes of glutamatergic synapses in hippocampus. A postsynaptic localization of BK channels was also supported by the finding that the channel coimmunoprecipitated with PSD95, a protein solely expressed in the postsynaptic compartment. These results thus demonstrate that BK channels reside in both post- and presynaptic compartments of hippocampal pyramidal neurons.
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http://dx.doi.org/10.1111/j.1460-9568.2006.04936.xDOI Listing
July 2006
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