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Abstract: A new metals-polymeric composite, Metx-EPS (I), was prepared to be used as catalyst in water or in two-phase aqueous conditions. The metals source was an exhausted catalytic converter that was grinded and treated with an acidic solution at room temperature. After filtration, the solution was concentrated, neutralized and added to a broth of Klebsiella oxytoca DSM 29614 to produce (I) where metals are embedded in a peculiar polysaccharide structure (EPS). The composite was easily recovered from the fermentation broth and purified. The process protocol was verified many times and was shown to be reproducible satisfactorily. The % recovery of metals, originally present in the converter, was good as determined by atomic absorption. The morphology and the chemical state of main metals in (I) were investigated by X-ray absorption spectroscopy methods (XANES and EXAFS). No metallic alloy seems to be evident. The catalytic activity and a possible synergic effect due to the presence of the different metals was valuated in the hydrogenation of some substrates, valuable precursors for theproduction of fine chemicals.
Keywords: Biogenerated polymetallic exopolysaccharide, biphasic catalysis, hydrogenation, metals-polymeric composite, new catalyst from metallic wastes, EXAFS, XANES
Published in RUNG: 06.05.2019; Views: 3202; Downloads: 0
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Abstract: Properties of mixed-metal MOFs depend on the distribution of different metals within their frameworks. Determination of this distribution is often very challenging. Using an example of aluminum- and iron-containing MIL-100, we demonstrate that 27Al NMR spectroscopy, when combined with first-principles calculations and magnetic, X-band electron paramagnetic resonance, Fe K-edge extended X-ray absorption fine structure, and Mössbauer measurements, enables one to accurately determine the arrangement of Al and Fe within the metal trimers, which are the basic building units of MIL-100. In this particular material, the incorporation of Fe and Al on the framework metal sites is random. Crucial for deciphering the arrangement is detecting NMR signals, shifted because of the strong hyperfine interaction between the 27Al nuclei and the unpaired electronic spins of Fe3+ ions, assigning the shifted signals aided by first-principles calculations of hyperfine couplings, and quantitatively evaluating the NMR intensities and the measured effective magnetic moment.
Keywords: Fe EXAFS, XANES, MIL100, MOF, magnetizem
Published in RUNG: 26.03.2019; Views: 3213; Downloads: 0
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Keywords: samoevalvacijsko poročilo
Published in RUNG: 20.12.2018; Views: 3623; Downloads: 0
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Abstract: The European Synchrotron and free-electron laser (FEL) User Organisation (ESUO) established in 2010 [1] today represents about 30.000 users. We aim at representing the users from all European countries. Each country is represented within ESUO by one up to four national delegate(s), depending on the size of the user community in the respective country. ESUO’s main objectives are (i) to promote an integrated approach throughout Europe for the use of European synchrotron and FEL facilities, (ii) to enable all European scientists to make use of the existing European synchrotron and FEL research infrastructures, solely based on scientific merit of their submitted proposals for beamtime requests, and this independently from the financial situation of the user (country), (iii) to facilitate open transnational access to European light sources through programmes of the European Union, (iv) to disseminate information about scientific opportunities and funding mechanisms for access to synchrotron and FEL facilities, and (v) to be a discussion and acting partner regarding the coordination of the synchrotron and FEL user activities within Europe. In the past few years, ESUO has contributed to several joint activities in the frame of successfully completed European FP7 projects such as ELISA (March 2009 - August 2011) and CALIPSO (June 2012 - May 2015). Some past ESUO activities concern, amongst others:  the user representation in e.g. the CALIPSO and BioStruct-X European projects by ESUO delegates;  the contribution to the CALIPSOplus project application;  the dissemination of ESUO activities by means of e.g. poster presentations and talks delivered at international conferences, specialized user meetings/workshops, and;  several initiatives which have been attended to promote transnational access activities [3] and to favor the continuation of transnational user access to national facilities in Europe within the new European Framework Program Horizon 2020 [4]. Today, chance is given to ESUO to keep constructively acting for the users in the frame of joint networking activities being part of the HORIZON 2020 project CALIPSOplus [5] (May 2017 – April 2021, Grant Agreement No 730872) coordinated by Helmholtz-Zentrum Dresden-Rossendorf (HZDR). In the framework of CALIPSOplus, ESUO is contributing to project networking activities which are, amongst others, shown in the present contribution. With the aim to further prepare the future science at European synchrotron and FEL user facilities, ESUO is contributing to the League of European Accelerator-based Photon Sources (LEAPS) initiative [6].
Keywords: European synchrotron user organisation, Transnational access, FEL, CALIPSO
Published in RUNG: 01.10.2018; Views: 3411; Downloads: 0
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Abstract: Sulfur based batteries are considered as very attractive energy storage devices. Sulfur is one of the most abundant elements in the earth, it is electrochemically active material which can accept up to two electrons per atom. In combination with alkali metals, sulfur forms electrochemical couples with much higher theoretical energy density compared to Li-ion batteries commonly available today. At the moment, the electrochemical couple with Li is most extensively studied. While the main principle of operation is known the relevant operation mechanism(s) is not completely clear. Even more promising is the electrochemical couple with Mg providing almost twofold higher volumetric energy density due to its ability to provide two electrons during oxidation. However, Mg-S batteries are still in the very early stage of research and development and the complex mechanism of sulfur conversion has been less extensively studied. In order to improve the understanding of sulfur electrochemical conversion and its interactions within electrode, we need to apply new experimental approaches capable to provide precise information about local environment of S in the cathode during battery operation. In our work, resonant inelastic X-ray scattering (RIXS) and XAS measurements at the sulfur K-edge performed in operando mode were used to study the lithium-polysulfide formation during the discharge process. Measurements were performed at ID26 beamline of the ESRF synchrotron using tender X-ray emission spectrometer [1]. Resonant excitation condition enhanced the sensitivity for the lithium−polysulfide detection. On the other hand, the sulfate signal from the electrolyte was heavily suppressed and the self-absorption effects minimized due to fixed excitation energy. This experimental methodology was used to provide quantitative analysis of sulfur compounds in the cathode of a Li−S battery cell during the discharge process [2]. The high-voltage plateau in the discharge curve was characterized by a rapid conversion of solid sulfur into liquid phase Li polysulfides reaching its maximum at the end of this plateau. At this point the starting point for the precipitation of the Li2S from the liquid polysulfide phase was observed. The same approach has been used also for the Mg-S battery revealing similar mechanism as in case of Li-S battery [3]. The electrochemical conversion of sulfur with magnesium proceeds through two well-defined plateaus, which correspond to the equilibrium between sulfur and Mg polysulfides (high-voltage plateau) and polysulfides and MgS (low-voltage plateau).
Keywords: Mg-Sulphur batteries, XANES, RIXS
Published in RUNG: 13.09.2018; Views: 4440; Downloads: 0
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