Keti Vezzù

Magnesium batteries are emerging as a cutting‐edge energy storage solution poised to revolutionize the battery industry. In this context, electrolytes play a pivotal role in the development of reliable and efficient devices. A family of new ionic liquid‐based electrolytes is proposed for potential application in magnesium batteries. These electrolytes are synthesized through the reaction of 1‐butyl‐1‐methylpyrrolidinium chloride (Pyr ₁₄ Cl), boron trichloride, and varying amounts of δ‐MgCl ₂ . The thermal, structural, and coordination properties of the proposed electrolytes are studied using density functional theory calculations, high resolution thermogravimetry, modulated differential scanning calorimetry, and Fourier transform infrared investigations. For the first time, the structure and nature of interactions characterizing the anionic and cationic domains of ionic liquid electrolytes, as a function of δ‐MgCl ₂ doping, are examined using BCl ₄ ⁻ as a spectroscopic “ion probe”. These results are combined with features of electric response, as well as structural and local relaxation events investigated through broadband electrical spectroscopy and nuclear magnetic resonance studies, respectively, to elucidate the unique characteristics and conductivity mechanisms of the proposed materials. Finally, the reasonably high ionic conductivity of these electrolytes at room temperature makes these materials very promising for application in magnesium battery prototypes.

Electrocatalytic water splitting holds promise for green hydrogen production, but its widespread adoption is challenged by the trade‐off between energy consumption and production costs. Iron‐triad‐based materials are of considerable interest as electrocatalysts due to their unique chemistry and electronic structure, which facilitate moderate intermediate adsorption energies and offer tolerance to site solvation and deactivation. However, the long‐term durability of those electrocatalysts remains poorly understood, hindering advanced progress. This review summarizes the fundamentals of water electrolysis chemistry, the challenges in evaluating the catalytic performance, and advances in modulating the chemistry of iron‐triad active sites for water splitting, with a focus on alkaline water electrolysis, particularly anion exchange membrane water electrolysis (AEMWE). It also discusses recent developments in iron‐triad electrocatalysts for water electrolysis under acidic conditions. A key emphasis is placed on the structure–activity relationships resulting from tailored iron‐triad active center chemistry. Furthermore, the review explores engineering strategies, such as near‐surface and chemical microenvironment modification to enable self‐healing, reconstruction, and alternative catalytic mechanisms, including the localized oxide path mechanism. Finally, it examines the challenges and future prospects of sustainable hydrogen production, including rational catalyst design, scalable synthesis techniques, and in‐depth physicochemical and electrochemical studies.

This work presents a simple and efficient methodology for the synthesis of well‐defined fluorinated copolyphosphazenes incorporating 2,2,2‐trifluoroethan‐1‐olate (–OCH₂CF₃, TFE) and 3‐(diethylamino)phenolate (3DEAP) side groups, randomly distributed along the polymer chains, via living cationic polymerization. Two fluorinated copolyphosphazenes, 4a and 4b, with different CF₃/3DEAP ratios (1:1 and 1:3, respectively), are prepared. The 3DEAP groups in these polymers are selectively and smoothly quaternized using methyl iodide (CH₃I), yielding cationic fluorinated copolyphosphazenes 5a and 5b with quaternization degrees of ≈80% and 90%, respectively. These cationic copolymers, featuring tailored CF₃/3DEMAP⁺ ratios (3DEMAP⁺ = 3‐(diethyl(methyl)ammonio)phenolate), exhibit complete water solubility and demonstrate self‐assembly in aqueous solutions, forming large compound micelles (LCMs) or bilayer vesicles depending on their composition. The amphiphilic nature of these materials, combining hydrophobic (CF₃) and hydrophilic (3DEMAP⁺) moieties, enables their application in the efficient capture of anionic pollutants, such as sodium diclofenac (SDF) and perfluorooctanoic acid (PFOA), commonly found in wastewater. This study highlights the potential of these cationic fluorinated copolyphosphazenes as promising candidates for water decontamination and environmental remediation.

Spinel‐structured transition metal (TM) oxides have shown great potential as a sustainable alternative to platinum group metal‐based electrocatalysts. Among them, high‐entropy oxides (HEOs) with multiple TM‐cation sites are suitable for engineering octahedral redox‐active centers to enhance the catalyst reactivity. This paper reports on the preparation of electrospun (Cr _1/5 Mn _1/5 Fe _1/5 Co _1/5 Ni _1/5 ) ₃ O ₄ nanofibers (NFs) and their evaluation as electrocatalysts. Its main aim is to unveil the nanostructural features that play a key role in the alkaline oxygen evolution reaction. Differing calcination temperature (300−800 °C) and duration (2 or 4 h) leads to different morphology of the NFs, crystallinity of the oxide, density of defects, and cation distribution in the lattice, which reflect in different electrocatalytic behaviors. The best performance (overpotential and Tafel slope at 10 mA cm ⁻² : 325 mV and 40 mV dec ⁻¹ , respectively) pertains to the NFs calcined at 400 °C for 2 h. To gain a deeper understanding of their electrocatalytic properties, the pristine NFs are investigated by a combination of analytical techniques. In particular, broadband electric spectroscopy reveals that the mobility of oxygen vacancies in the best electrocatalyst is associated to very fast local dielectric relaxations of metal coordination octahedral geometries and experimentally demonstrates the key role of O‐deficient octahedra.

Poly(oxyethylene) (POE) is frequently used as suitable component to prepare solid polymer electrolytes (SPEs), due to its: (i) ability to coordinate and dissociate doping salts; (ii) good mechanical properties; and (iii) high chemical and electrochemical stability. With the aim to obtain calcium secondary batteries, here we describe the preparation and studies of crosslinked Ca‐polycondensate (NPCY) electrolytes with formula NPCY/(CaTf₂)_x based on fragments of POE chains and CaTf₂. The molecular weight of POE precursors is Y=400 and 1000 g ⋅ mol⁻¹. The effect of POE molecular weight on the thermal, structural, and electrical properties of NPCY/(CaTf₂)_x is investigated revealing that in mesoscale this materials show: (i) two different nanodomains with polyether chains both “free” (not coordinating the cation) and involved in 4–4 coordination cages of Ca²⁺ metal ions; (ii) f_α‐fast, f_α‐cross and f_α‐slow relaxation modes of polyether chains, detected by broadband electrical spectroscopy, which are coupled with the long‐range charge migration pathways of SPEs; (iii) that triflate (Tf⁻) anions, which act as plasticizers, modulate the inter‐chain migration processes of Ca²⁺ between polyether coordination sites. Finally, the conductivity values of NPCY/(CaTf₂)_x, which is up to 10⁻⁴ S ⋅ cm⁻¹ at 80 °C, classify NPCY/(CaTf₂)_x as promising SPEs for the development of calcium secondary batteries.

Perovskite-type solid-state electrolytes, Li_3x La_2/3-x TiO₃ (LLTO), are considered among the most promising candidates for the development of all-solid-state batteries based on lithium metal. Their high bulk ionic conductivity can be modulated by substituting part of the atoms hosted in the A- or B-site of the LLTO structure. In this work, we investigate the crystal structure and the long-range charge migration processes characterizing a family of perovskites with the general formula La_1/2+1/2x Li_1/2-1/2x Ti_1-x Al _x O₃ (0 ≤ x ≤ 0.6), in which the charge balance and the nominal A-site vacancies (n _A = 0) are preserved. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) investigations reveal the presence of a very complex nanostructure constituted by a mixture of two different ordered nanoregions of tetragonal P4/mmm and rhombohedral R3̅c symmetries. Broadband electrical spectroscopy studies confirm the presence of different crystalline domains and demonstrate that the structural fluctuations of the BO₆ octahedra require to be intra- and intercell coupled, to enable the long-range diffusion of the lithium cation, in a similar way to the segmental mode that takes place in polymer-ion conductors. These hypotheses are corroborated by density functional theory (DFT) calculations and molecular dynamic simulations.

New inorganic‐organic hybrid anion exchange membranes are produced after incorporation of tantalum oxide into trimethylammonium‐functionalized polyethylene pyrrole‐co‐polyethylene ketone (functionalized polyketone, FPK), obtained by the chemical modification of a polyketone polymer. The influence of tantalum oxide fillers on the properties of the synthesized membranes is investigated. The interaction between inorganic fillers and the polymer chains is studied using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR‐FTIR). The thermal analysis of the FPK membranes reveals they are thermally stable at up to 250°C. However, the incorporation of the inorganic fillers reduces the thermal stability. Modulated Differential Scanning Calorimetry (MDSC) results indicate that the inclusion of inorganic fillers leads to an increase in crystallinity. This study reports that the properties of the bulk polymer can be tuned by controlling the degree of functionalization and content of inorganic fillers, as confirmed by Near Ambient Pressure X‐Ray Photoelectron Spectroscopy (NAP‐XPS) studies. Finally, Broadband Electrical Spectroscopy (BES) studies demonstrate that the hybrid membranes are characterized by several polarization phenomena contributing to the overall ion conductivity of the material, which at RT is of 1.46 and 1.61 mS cm⁻¹ for the FPK cast membrane and the hybrid membrane with 5.0 wt.% of Ta₂O₅ filler, respectively.

Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, then O₂-reduction often proceeds at a less positive potential, and produces higher amounts of undesirable H₂O₂-intermediate. Hybrid supports, which utilize metal oxides (e.g., CeO₂, WO₃, Ta₂O₅, Nb₂O₅, and ZrO₂), stabilize Pt and carbon nanostructures and diminish their corrosion while exhibiting high activity toward the four-electron (most efficient) reduction in oxygen. Porosity of carbon supports facilitates dispersion and stability of Pt nanoparticles. Alternatively, the Pt-based bi- and multi-metallic catalysts, including PtM alloys or M-core/Pt-shell nanostructures, where M stands for certain transition metals (e.g., Au, Co, Cu, Ni, and Fe), can be considered. The catalytic efficiency depends on geometric (decrease in Pt–Pt bond distances) and electronic (increase in d-electron vacancy in Pt) factors, in addition to possible metal–support interactions and interfacial structural changes affecting adsorption and activation of O₂-molecules. Despite the stabilization of carbons, doping with heteroatoms, such as sulfur, nitrogen, phosphorus, and boron results in the formation of catalytically active centers. Thus, the useful catalysts are likely to be multi-component and multi-functional.

In this report, the conductivity mechanism of Ca²⁺‐ion in polyoxyethylene (POE) solid polymer electrolytes (SPEs) for calcium secondary batteries is investigated by broadband electrical spectroscopy studies. SPEs are obtained by dissolving into the POE hosting matrix three different calcium salts: CaTf₂, Ca(TFSI)₂ and CaI₂. The investigation of the electric response of the synthetized SPEs reveals the presence in materials of two polarization phenomena and two dielectric relaxation events. It is demonstrated that the nature of the anion (i. e., steric hindrance, charge density and ability to act as coordination ligand) and the density of “dynamic crosslinks” of SPEs is fundamental in the establishment of ion‐ion/ion‐polymer interactions. The long‐range charge migration processes occurring along the two revealed percolation pathways of the electrolytes are generally coupled with the polymer host dynamics and depend on the temperature and the anion nature. This study offers the needed tools for understanding Ca²⁺ conduction in POE‐based electrolytes.