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The combined use of the X-ray Absorption Spectroscopy (XAS) and Powder X-Ray diffraction (PXRD) techniques in operando mode at both MCX and XAFS beamlines of ELETTRA will be complemented by ex situ TEM studies at the National Institute of Material Physics in Bucharest. The XAFS and PXRD study will be performed in operando mode and will permit to monitor both structural and electronic modification during a full galvanostatic cycle. The electron microscopy will provide a suitable microstructural and morphological characterization of selected samples.
No full textThe combined use of the X-ray Absorption Spectroscopy (XAS) and Powder X-Ray diffraction (PXRD) techniques in operando mode at both MCX and XAFS beamlines of ELETTRA will be complemented by ex situ TEM studies at the National Institute of Material Physics in Bucharest. The XAFS and PXRD study will be performed in operando mode and will permit to monitor both structural and electronic modification during a full galvanostatic cycle. The electron microscopy will provide a suitable microstructural and morphological characterization of selected samples
Metal Hexacyanoferrates: Ion Insertion (or Exchange) Capabilities
No full textMetal hexacyanoferrates are mixed-valence compounds characterized by open 3D frameworks that confer a variety of properties and allow the applicability in several fields. In this chapter, we focused on ion exchange capabilities. In the first instance, we examined diffusion-driven processes. Secondly, we addressed to electrochemically driven processes, reviewing the main currently used methods and applications
XAFS studies on battery materials: Data analysis supported by a chemometric approach
Full text linkThe large amount of data collected during a typical operando X-ray absorption fine structure (XAFS) experiment and the interest to thoroughly investigate and comprehend a redox process occurring in a Li-ion battery need an advanced data analysis approach. In this context, multivariate curve resolution (MCR) has gained attention as chemometric technique that allows the identification of the number of the species and their existence range without any a priori information on the studied system. The call for an advanced data treatment is answered by a joint XAFS-MCR approach, able to unveil the local structural dynamics of the selected species, providing a quick and efficient data interpretation
Concentrated Electrolytes Enabling Stable Aqueous Ammonium‐Ion Batteries
Full text linkRechargeable aqueous batteries are promising devices for large-scale energy-storage applications because of their low-cost, inherent safety, and environmental friendliness. Among them, aqueous ammonium-ion (NH) batteries (AAIB) are currently emerging owing to the fast diffusion kinetics of NH. Nevertheless, it is still a challenge to obtain stable AAIB with relatively high output potential, considering the instability of many electrode materials in an aqueous environment. Herein, a cell based on a concentrated (5.8 m) aqueous (NH)SO electrolyte, ammonium copper hexacyanoferrate (N-CuHCF) as the positive electrode (cathode), and 3,4,9,10-perylene-bis(dicarboximide) (PTCDI) as the negative electrode (anode) is reported. The solvation structure, electrochemical properties, as well as the electrode–electrolyte interface and interphase are systematically investigated by the combination of theoretical and experimental methods. The results indicate a remarkable cycling performance of the low-cost rocking-chair AAIB, which offers a capacity retention of ≈72% after 1000 cycles and an average output potential of ≈1.0 V
Thin layer films of copper hexacyanoferrate: Structure identification and analytical applications
No full textThin films of copper hexacyanoferrate (CuHCF) have been reproducibly electrodeposited on conductive substrates according to two different potentiostatic methods, here denoted as A and B. For both methods two consecutive steps are involved, the first being the electrodeposition of a thin Cu layer, the second its partial dissolution and formation of CuHCF in presence of hexacyanoferrate anion, giving as result a two layers film (CuHCF on Cu metal). The main difference, instead, consists in the applied potential values and their application times, featuring Method A lower potentials but longer processing times. Structural insights have been achieved by means of X-ray Diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) measurements, from which we can deduce the presence of Prussian blue (PB) impurities in Method A, while Method B leads to a pure CuHCF phase. Two analytical applications have been considered, ion exchange and H2O2 sensing. Ion exchange has been first assayed and, although CuHCF-A shows a higher stability towards multivalent cations, CuHCF-B is suitable for small hydrated ions. PB impurities in CuHCF-A boost its sensing towards H2O2, making it more adapted to this employment
Metal Hexacyanoferrate Absorbents for Heavy Metal Removal
No full textAlternative energy sources are currently worldwide under development
to contribute to the increasing energy demand. Along with the introduction of new
technologies, heavy metals, such as radionuclides from nuclear power plant leaks,
might be released into the environment and contaminate waters, air, and soil. Among
the investigated methods, the use of adsorbents has been proven the most suitable
one, able to extensively remove heavy metals, e.g., radioactive 137Cs+. Prussian blue
analogs (PBAs) have been demonstrated to be effective adsorbents toward the
sequestration of a variety of heavy metals, including the recovery and valorization
of rare earth elements. Here, we point out the structure-property link of PBAs: the large channels and cavities are able to accommodate a variety of ions, ranging from
monovalent to multivalent ones, while the ion exchange may be either diffusioncontrolled or electrochemically driven. While distribution coefficients are shown to
be key parameters in the diffusion driven process, resulting in high affinities of
PBAs toward metals such as Cs+, Tl+, Cu2+, and Zn2+, electrochemical ion exchange
is considered to be promising due to the effectiveness in the removal of metals and
the possibility to reversibly restore the adsorbent to its initial state. Related examples concerning the capture of Cs+ from wastewaters and the recovery of rare earth
elements are herein presented and commented
Highlighting the Reversible Manganese Electroactivity in Na‐Rich Manganese Hexacyanoferrate Material for Li‐ and Na‐Ion Storage
Full text linkThe electroactivity of sodium‐rich manganese hexacyanoferrate (MnHCF) material constituted of only abundant elements, as insertion host for Li‐ and Na‐ions is herein comprehensively discussed. This material features high specific capacities (>130 mAh g−1) at high potentials when compared to other materials of the same class, i.e., Prussian blue analogs. The reversible electronic and structural modifications occurring during ion release/uptake, which are responsible for such high specific capacity, are revealed herein. The in‐depth electronic and structural analysis carried out combining X‐ray diffraction and X‐ray absorption spectroscopy (XAS), demonstrates that both Fe and Mn sites are involved in the electrochemical process, being the high delivered capacity the result of a reversible evolution in oxidation states of the metallic centers (Fe3+/Fe2+ and Mn2+/Mn3+). Along with the Mn2+/Mn3+ oxidation, the Mn local environment experiences a substantial yet reversible Jahn–Teller effect, being the equatorial Mn‐N distances shrunk by 10% (2.18 Å → 1.96 Å). Na‐rich MnHCF material offers slightly higher performance upon uptake and release of Na‐ions (469 Wh kg−1) than Li‐ions (457 Wh kg−1), being, however, the electronic and structural transformation independent of the adopted medium, as observed by XAS spectroscopy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Synthesis, characterization and formulation of a cathode active material: Copper nitroprusside
Full text linkNowadays, rechargeable Li-ion batteries play an important role in portable consumer devices. Formulation of such batteries is improvable by researching new cathodic materials that present higher performances of cyclability and negligible efficiency loss over cycles.
Goal of this work was to investigate a new cathodic material, copper nitroprusside, which presents a porous 3D framework. Synthesis was carried out by a low-cost and scalable co-precipitation method. Subsequently, the product was characterized by means of different techniques, such as TGA, XRF, CHN elemental analysis, XRD, Mössbauer spectroscopy and cyclic voltammetry. Electrochemical tests were finally performed both in coin cells and by using in situ cells: on one hand, coin cells allowed different formulations to be easily tested, on the other operando cycling led a deeper insight to insertion process and both chemical and physical changes. Results of several tests highlighted a non-reversible electrochemical behavior of the material and a rapid capacity fading over time. Moreover, operando techniques report that amorphisation occurs during the discharge
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