1,720,987 research outputs found
SURFACE DYNAMIC OF COPPER NITROPRUSSIDE AS A CATHODE MATERIAL: OBSERVATION BY XPS AND SEM
No full textTHE UNCOMMON ELECTROCHEMISTRY OF COPPER NITROPRUSSIDE DISCLOSED BY SPECTROSCOPIC AND DIFFRACTION TECHNIQUES
No full textOn the Dynamics of Battery Materials Revealed by Operando XRD and XAS
No full textAffordable energy is a crucial factor for sustainable economic growth. The electrochemical energy storage plays a major societal role due to its widespread technological applications. Host nanostructured materials have a crystal structure with insertion sites, channels and/or interlayer spacings allowing the rapid insertion and extraction of lithium ions with generally little lattice strain, making them useful as electrode materials for batteries. Dynamic processes occurring in batteries can be studied by operando modality, which provide a realistic representation of the electrochemical reactions occurring at the electrodes, allowing to check the structural and electronic reversibility of a battery system while at least one full cycle is performed. For all these reasons, ex situ studies, which reflect a given state of charge (SOC) of electrode materials are complemented by operando measurements using complementary techniques such as X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). X-ray absorption spectroscopy is a synchrotron radiation based technique that provide both electronic and structural information on a selected atom. Operando synchrotron radiation x-ray powder diffraction (SR-XRPD) experiments allow monitoring the periodic structure of a material during the intercalation/release process of ions. The potentiality of the joint XAS-XRD approach in the newly proposed Prussian blue analogues (PBA) cathodes materials for rechargeable batteries is here highlighted, giving emphases on the copper hexacyanoferrate, copper nitroprusside, and manganese hexacyanoferrate. As an example, manganese hexacyanoferrate (MnHCF) is made of earth-abundant elements by a safe and easy synthesis and features high specific capacities at a higher potential than other PBAs. Na-rich MnHCF was tested in both Li- and Na-ion organic electrolytes in a post-Li strategy perspective and investigated using XAS and XRPD. Both Fe and Mn sites are involved in the electrochemical process, and the high delivered capacity (>130 mAh g-1) results from a reversible evolution in the metallic centers’ oxidation states (Fe3+/Fe2+ and Mn2+/Mn3+). Along with the Mn2+/Mn3+ oxidation, the Mn local environment experiences a substantial yet reversible Jahn–Teller (JT) effect, detected by the spectroscopic technique: the EXAFS shows a substantial and reversible basal contraction (10%) in the charged states due to the equatorial Mn-N bonds’ shortening (2.18 Å → 1.96 Å). Furthermore, operando XRD highlights a non-cooperative JT (NCJT) distortion. The lattice volume expands only by 2% upon electrochemical alkali-ion removal and insertion, which contrasts with EXAFS-retrieved Mn−N distances. This apparent disagreement underlines the capability of the PBA open framework to mitigate and disperse the pronounced variation of the JT-active Mn3+, granting overall stability to the structure. XANES. The dynamic of the ions insertion/release electrochemical reaction was further investigated by analysing the full XAS dataset by a multivariate curve resolution with alternating least squares algorithm (MCR-ALS), with the intent to assess the number of species involved and their evolutions during the electrochemical process
The peculiar redox mechanism of copper nitroprusside disclosed by a multi-technique approach
No full textNewly developed electrochemical synthesis of Co-based Layered Double Hydroxides: application to 5-(hydroxymethyl)furfural electrooxidation
No full textTitanium activation in prussian blue based electrodes for Na-ion batteries: A synthesis and electrochemical study
Full text linkSodium titanium hexacyanoferrate (TiHCF, Na0 Ti [Fe(CN)]·3HO) is synthesized by a simple co-precipitation method in this study. Its crystal structure, chemical composition, and geometric/electronic structural information are investigated by X-ray powder diffraction (XRPD), microwave plasma-atomic emission spectroscopy (MP-AES), and X-ray absorption spectroscopy (XAS). The electroactivity of TiHCF as a host for Li-ion and Na-ion batteries is studied in organic electrolytes. The results demonstrate that TiHCF is a good positive electrode material for both Li-ion and Na-ion batteries. Surprisingly, however, the material shows better electrochemical performance as a Na-ion host, offering a capacity of 74 mAh g at C/20 and a 94.5% retention after 50 cycles. This is due to the activation of Ti towards the redox reaction, making TiHCF a good candidate electrode material for Na-ion batteries
Newly developed electrochemical synthesis of Co-based layered double hydroxides: toward noble metal-free electro-catalysis
No full textA novel and enhanced electrosynthesis protocol that allows the deposition of thin films of Co/Al and Co/Fe layered double hydroxides (LDHs) on different supports is hereby proposed. The approach is based on potentiodynamic cathodic reduction. All the films have been characterised by cyclic voltammetry, powder X-ray diffraction, scanning electron microscopy, and Raman and atomic emission spectroscopies. Moreover, LDHs electrosynthesised on carbonaceous materials have also beeninvestigated by X-ray absorption spectroscopy to analyse their local metal structure. These substrates are particularly interesting for the plethora of LDH applications ranging from energy storage, sensing, and electrocatalysis, and are also of industrial importance, due to their low cost, ecocompatibility, and easy
handling. In particular, the material was exploited for 5-(hydroxymethyl)furfural (HMF) electro-oxidation
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
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