1. In-situ XAS study of catalytic N[sub]2O decomposition over CuO/CeO[sub]2 catalystsMaxim Zabilsky, Iztok Arčon, Petar Djinović, Elena Tchernychova, Albin Pintar, 2021, original scientific article Abstract: We performed in‐situ XAS study of N 2 O decomposition over CuO/CeO 2 catalysts. The Cu K‐edge and Ce L 3 ‐edge XANES and EXAFS analyses revealed the dynamic and crucial role of Cu 2+ /Cu + and Ce 4+ /Ce 3+ ionic pairs during the catalytic reaction. We observed the initial formation of reduced Cu + and Ce 3+ species during activation in helium atmosphere at 400 °C, while concentration of these species decreased significantly during steady‐state nitrous oxide degradation reaction (2500 ppm N 2 O in He at 400 °C). In‐situ EXAFS analysis further revealed a crucial role of copper‐ceria interface in this catalytic reaction. We observed dynamic changes in average number of Cu‐Ce scatters under reaction conditions, indicating an enlarging the interface between both copper and ceria phases, where electron and oxygen transfer occurs.
Keywords: in-situ XAS, Cu EXAFS, CuO/CeO2 nanorod catalys, N2O decomposition
Published in RUNG: 29.01.2021; Views: 3930; Downloads: 0
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2. Ceramic synthesis of disordered lithium rich oxyfluoride materialsJean-Marcel Ateba Mba, Iztok Arčon, Gregor Mali, Elena Tchernychova, Ralf Witte, Robert Kruk, Miran Gaberšček, Robert Dominko, 2020, original scientific article Abstract: Disordered lithium-rich transition metal oxyfluorides with a general formula Li1þxMO2Fx (M being a transition
metal) are gaining more attention due to their high specific capacity which can be delivered from the facecentered
cubic (fcc) structure. The most common synthesis procedure involves use of mechanosynthesis. In
this work, ceramic synthesis of lithium rich iron oxyfluoride and lithium rich titanium oxyfluoride are reported.
Two ceramic synthesis routes are developed each leading to the different level of doping with Li and F and
different levels of cationic disorder in the structure. Three different Li1þxMO2Fx samples (x ¼ 0.25, 0.3 and 1) are
compared with a sample prepared by mechanochemical synthesis and non-doped LiFeO2 with fcc structure. The
obtained lithium rich iron oxyfluoride are characterized by use of M€ossbauer spectroscopy, X-ray absorption
spectroscopy, NMR and TEM. Successful incorporation of Li and F have been confirmed and specific capacity that
can be obtained from the samples is in the correlation with the level of disorder introduced with doping,
nevertheless oxidation state of iron in all samples is very similar. Conclusions obtained from lithium rich iron
oxyfluoride are validated by lithium rich titanium oxyfluoride.
Keywords: Lithium batteries
Face centered-cubic
Oxyfluoride
Li-rich
Disorder
Published in RUNG: 05.06.2020; Views: 5261; Downloads: 0
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3. Effects of a Mixed O/F Ligand in the Tavorite-Type LiVPO4O StructureSorour Semsari Parapari, Jean-Marcel Ateba Mba, Elena Tchernychova, Gregor Mali, Iztok Arčon, Gregor Kapun, Mehmet Ali Gülgün, Robert Dominko, 2020, original scientific article Abstract: We report the synthesis and detailed structural
and chemical characterization including electrochemical
properties of a lithium vanadium oxy/fluoro-phosphate
material. To the best of our knowledge, we have for the first
time synthesized a LiVPO4O-type phase with a mixed O/F
ligand. In the synthesis procedure, the LiVPO4O precursor
compound was fluorinated via LiF incorporation, with
preservation of the LiVPO4O framework structure. The
operating potential of the synthesized material is increased
compared to that of the LiVPO4O precursor (4.12 V vs 3.95 V
versus metallic lithium, respectively). The related increase in
operating potential was assigned to the effect of the
intermixing O/F ligand, which is attained via the successful
fluorine incorporation into the LiVPO4O structure. A characterization of the investigated materials was performed using
microscale-covering XRD, XANES, and NMR techniques as well as nanoscale spatially resolved imaging and analytical STEM
techniques. The obtained oxy/fluoro-phosphate phase is isostructural to LiVPO4O; however, the presence of the mixed O/F
ligand promoted a higher symmetry of vanadium octahedra. These variations of the vanadium local environment along with the
observed inhomogeneous distribution of the incorporated fluorine gave rise to the minor local deviations in vanadium valence.
Our results clearly emphasize the connection among the fluorine ligand incorporation, its local distribution, and the
electrochemical properties of the material.
Keywords: LiVPO4O, XRD, SEM, V XANES, Tavorite-Type, electrochemical properties
Published in RUNG: 17.02.2020; Views: 3757; Downloads: 0
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4. The mechanism of Li2S activation in lithium-sulfur batteries: Can we avoid the polysulfide formation?Alen Vižintin, Laurent Chabanne, Elena Tchernychova, Iztok Arčon, Lorenzo Stievano, Giuliana Aquilanti, Markus Antonietti, Tim-Patric Fellinger, Robert Dominko, 2017, original scientific article Abstract: Electrochemical reactions in the LieS batteries are considered as a multistep reaction process with at least
2e3 equilibrium states. Here we report a possibility of having a conversion of Li2S into sulfur without
detectible formation of polysulfides. That was confirmed by using a novel material system consisting of
carbon coated Li2S particles prepared by carbothermal reduction of Li2SO4. Two independent in operando
measurements showed direct oxidation of Li2S into sulfur for this system, with almost negligible formation
of polysulfides at potentials above 2.5 V vs. Li/Liþ. Our results link the diversity of first charge profiles in the
literature to the Li2S oxidation mechanism and show the importance of ionic wiring within the material.
Furthermore, we demonstrate that the Li2S oxidation mechanism depends on the relative amount of
soluble sulfur in the electrolyte. By controlling the type and the amount of electrolyte within the encapsulating
carbon shell, it is thereby possible to control the reaction mechanism of Li2S activation.
Keywords: Lithium-sulfur batteries
Li2S active material
XAS
UV/Vis spectroscopy
Li2S activation
Published in RUNG: 03.03.2017; Views: 6242; Downloads: 0
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