31. Correlation between FeCl2 electrolyte conductivity and electrolysis efficiencyUroš Luin, Matjaž Valant, Iztok Arčon, 2022, published scientific conference contribution abstract Abstract: The electrolysis efficiency is an important aspect of the Power-to-Solid energy storage technology (EST) based
on the iron chloride electrochemical cycle [1]. This cycle employs an aqueous FeCl2 catholyte solution for the
electro-reduction of iron. The metal iron deposits on the cathode. The energy is stored as a difference in the
redox potential of iron species. Hydrogen, as an energy carrier, is released on demand over a fully controlled
hydrogen evolution reaction between metallic Fe0 and HCl (aq) [1]. Due to these characteristics, the cycle is
suitable for long-term high-capacity and high-power energy storage. In a previous work [2] we revealed that
the electrolyte conductivity linearly increases with temperature. Contrary, the correlation between the
electrolyte concentration and efficiency is not so straightforward. Unexpectedly small efficiency variations were
found between 1 and 2.5 mol dm-3 FeCl2 (aq) followed by an abrupt efficiency drop at higher concentrations.
To explain the behavior of the observed trends and elucidate the role of FeCl2 (aq) complex ionic species we
performed in situ X-ray absorption studies. We made a dedicated experimental setup, consisting of a tubular
oven and PMMA liquid absorption cell, and performed the measurements at the DESY synchrotron P65
beamline. The XAS investigation covered XANES and EXAFS analyses of FeCl2 (aq) at different
concentrations (1 - 4 molL-1) and temperatures (25 - 80 °C). We found that at low temperature and low FeCl2
concentration the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33
(±0.02) Å and five water molecules at a distance of 2.095 (±0.005) Å [3]. The structure of the ionic complex
gradually changes with an increase in temperature and/or concentration. The apical water molecule is
substituted by a chlorine ion to yield a neutral Fe[Cl2(H2O)4]0. The transition from the single charged
Fe[Cl(H2O)5]+ to the neutral Fe[Cl2(H2O)4]0 causes a significant drop in the solution conductivity, which well
correlates with the existing conductivity models [3].
[1] M. Valant, “Procedure for electric energy storage in solid matter. United States Patent and
Trademark Office. Patent No. US20200308715,” Patent No. US20200308715, 2021.
[2] U. Luin and M. Valant, “Electrolysis energy efficiency of highly concentrated FeCl2 solutions
for power-to-solid energy storage technology,” J. Solid State Electrochem., vol. 26, no. 4, pp.
929–938, Apr. 2022, doi: 10.1007/S10008-022-05132-Y.
[3] U. Luin, I. Arčon, and M. Valant, “Structure and Population of Complex Ionic Species in
FeCl2 Aqueous Solution by X-ray Absorption Spectroscopy,” Molecules, vol. 27, no. 3, 2022,
doi: 10.3390/molecules27030642.
Keywords: Iron chloride electrochemical cycle, Power-to-Solid energy storage, XANES, EXAFS, electrical
conductivity, electrolyte complex ionic species structure and population
Published in RUNG: 26.09.2022; Views: 1800; Downloads: 0 (1 vote)
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32. Cationic Covalent Organic Polymer Thin Film for Label-free Electrochemical Bacterial Cell DetectionTina Skorjanc, Andraž Mavrič, Mads Nybo Sorensen, Gregor Mali, Changzhu Wu, Matjaž Valant, 2022, original scientific article Keywords: Bacteria, Electrical properties, Electrochemical cells, Electrodes, Sensors
Published in RUNG: 26.09.2022; Views: 1338; Downloads: 27
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33. Covalent polymer thin films for biosensor applicationsTina Skorjanc, Andraž Mavrič, Mads Nybo Sorensen, Gregor Mali, Changzhu Wu, Matjaž Valant, 2022, published scientific conference contribution abstract Keywords: bacteria, sensing, electrochemical impedance spectroscopy, electrophoresis, electrode preparation, Menshutkin reaction
Published in RUNG: 26.09.2022; Views: 1372; Downloads: 0
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34. Deposition of porphyrin thin films by electrophoresisAndraž Mavrič, Tina Škorjanc, Mads Nybo Sørensen, Changzhu Wu, Matjaž Valant, 2022, published scientific conference contribution abstract Abstract: Porphyrins are heterocyclic macrocycles consisting of interconnected pyrrole subunits acting as ligands for metal ions. Metallised metalloporphyrins naturally occur as cofactors in a series of enzymes, acting as active sites for biochemical transformations. Mimicking nature, a variety of functionalized porphyrins have been prepared for different catalytic purposes [1]. These organometallic complexes have isolated metal centers in tailored coordination environments to drive catalytic reactions in homogeneous solutions. The activity and selectivity of isolated metal ions acting as single-atom catalysts are defined by the coordination environment.
Depending on the porphyrin structure, the solubility of these macrocycles and their processability in solutions can be altered. While such adjustments to the structure might ease the processability, the catalytic properties might also be altered. Because homogenous catalysis presents challenges with the separation and recyclability of the catalyst, it is common to fix metalloporphyrins into molecular organic frameworks or deposit them onto a substrate. Commonly used deposition techniques face several challenges. For instance, thermal evaporation can cause partial or complete degradation of some thermally-labile functional groups attached to the porphyrins. Similarly, spin coating commonly results in an uneven thickness and uneven morphology of the deposited films.
To overcome these difficulties, we present an alternative method for the deposition of porphyrin thin films that is suitable for a wide range of functionalized porphyrins. The electrophoresis can force the molecules to deposit on a conductive substrate such as a metal foil or transparent conductive oxide by applying the electric field generated by a DC power supply. The film thickness can be precisely controlled by changing the voltage value, deposition time, or solution concentration using even a small amount of material [2, 3]. Six different functionalized porphyrin molecules have been successfully deposited onto the copper foil substrate by optimizing key parameters, including applied electric field, the duration of electrophoresis, the size of the copper electrodes, and solvent polarity. To demonstrate the generality of our approach, we have selected a broad range of porphyrins that incorporate the following functional groups: phenyl rings, carboxylic acids, pyridyl rings, methyl benzyl ethers, methyl benzoyl esters, and cobalt (II) metalized macrocycle. The impact of this study extends above catalysis to various applications of porphyrins thin films on conductive substrates such as optoelectronics and sensors.
Keywords: porphyrin, thin film, electrophoresis
Published in RUNG: 26.09.2022; Views: 1267; Downloads: 0
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36. Iron phosphide precatalyst for electrocatalytic degradation of rhodamine B dye and removal of Escherichia coli from simulated wastewaterTakwa Chouki, Manel Machreki, Jelena Topić, Lorena Butinar, Plamen Stefanov, Erika Jež, Jack S. Summers, Matjaž Valant, Aaron Fait, Saim Emin, 2022, original scientific article Keywords: železov fosfat, elektrokataliza, rodamin
Published in RUNG: 02.08.2022; Views: 1634; Downloads: 96
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40. O[sub]2 loaded germanosilicate optical fibers : experimental in situ investigation and ab initio simulation study of GLPC evolution under irradiationImène Reghioua, Luigi Giacomazzi, Antonino Alessi, Blaž Winkler, Layla Martin-Samos, Sylvain Girard, Diego Di Francesca, Mattia Fanetti, Nicolas Richard, Matjaž Valant, 2022, original scientific article Keywords: optical fiber, O2 loading, point defects
Published in RUNG: 25.04.2022; Views: 1734; Downloads: 29
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