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Pr1-xSrxFe0.8Ni0.2O3-δ (x=0.1, 0.2, and 0.3) polycrystalline phases were prepared by combustion synthesis. Their magnetic properties and Mössbauer effect have been examined in the range 5–300 K. Mössbauer spectroscopy shows the existence of charge disproportionation in several of the samples at low temperatures. Meanwhile, the samples present multiple features pointing out a frustrated magnetic order, with competing ferro- and antiferromagnetic interactions. Additionally, exchange bias (EB) phenomena have been observed. Hence, when the samples are cooled in a static magnetic field down to temperatures below 50 K, the hysteresis loops shift in the opposite direction to the applied biasing field, with shifts up to 10 kOe and more, and a small vertical shift of the loops also appears. This behavior seems linked to spin disorder and to the appearance of ferromagnetic (FM) ordered regions at low temperatures when cooling with a high applied field. The growth of these FM regions is likely due to the aligning role of an important cooling magnetic field over Ni-Fe and Fe5+-Fe3+ FM interactions. The higher FM contributions and therefore EB values found in the samples presenting charge disproportionation are related to the formation of FM regions in Fe5+-rich areas. [ABSTRACT FROM AUTHOR]

Abstract: Ionic–electronic conductor composite materials are widely employed to improve the ionic conductivity of solid oxide fuel cell electrodes, making them more compatible with the solid oxide fuel cell materials. The addition of an ionic conductor implies, however, a decrease of the cathode active area for the oxygen reduction reactions. In addition, the ionic conductor particles are usually dispersed and isolated, limiting the enhanced properties to certain areas. In order to avoid this drawback and improve the ionic conductivity of the electrode, vertically aligned carbon nanotubes (VACNTs) have been synthesized and employed as template for the deposition of Sm0.2Ce0.8O2 (SDC) particles. Subsequently, these SDC-VACNTs have been coated with a Pr0.6Sr0.4Fe0.8Co0.2O3 (PSFC) perovskite phase, leading to the formation of the desired composite material. Attending to the obtained results, it is proved that the new composite material exhibits a significantly better electrochemical performance, due to a better distribution of the ionic conductor and the burning of the carbon nanotubes (CNTs), which result in the improvement of the microstructure. [Copyright &y& Elsevier]

A novel organic ionic plastic crystal (OIPC) based on a quaternary ammonium cation and a tetrachloroferrate anion has been synthesized with the intention of combining the properties of the ionic plastic crystal and the magnetism originating from the iron incorporated in the anion. The thermal analysis of the obtained OIPC showed a solid–solid phase transition below room temperature and a high melting point above 220 °C, indicating their plastic crystalline behaviour over a wide temperature range, as well as thermal stability up to approximately 200 °C. The magnetization measurements show the presence of three-dimensional antiferromagnetic ordering below 4 K. The results from electrochemical characterization display a solid-state ionic conduction sufficiently high and stable (between 10−2.7 and 10−3.6 S cm−1 from 20 to 180 °C) for electrochemical applications. [ABSTRACT FROM AUTHOR]

Abstract: Sample of nominal composition La0.6Ca0.4Fe0.8Ni0.2O3 (LCFN) was prepared by liquid mix method. The structure of the polycrystalline powder was analyzed with X-ray powder diffraction data. This compound shows orthorhombic perovskite structure with a space group Pnma. In order to improve the electrochemical performance, Sm-doped ceria (SDC) powder was added to prepare the LCFN–SDC composite cathodes. Electrochemical characteristics of the composites have been investigated for possible application as cathode material for an intermediate-temperature-operating solid oxide fuel cell (IT-SOFC). The polarization resistance was studied using Sm-doped ceria (SDC). Electrochemical impedance spectroscopy measurements of LCFN–SDC/SDC/LCFN–SDC test cell were carried out. These electrochemical experiments were performed at equilibrium from 850°C to room temperature, under both zero dc current intensity and air. The best value of area-specific resistance (ASR) was for LCFN cathode doped with 10% of SDC (LCFN–SDC9010), 0.13Ωcm2 at 850°C. The dc four-probe measurement exhibits a total electrical conductivity over 100Scm−1 at T ≥600°C for LCFN–SDC9010 composite cathode. [Copyright &y& Elsevier]

Abstract: Polycrystalline samples of Gd0.8Sr0.2Fe0.8M0.2O3 (M=Cr, Ga) are prepared by combustion route and pore wetting technique in order to compare the influence of the morphology in the performance of two cathodes for Solid Oxide Fuel Cells. When polycarbonate membranes are used as templates nanowire arrays with a diameter of 50–70 nm are obtained. Comparing the results obtained by Electrochemical Impedance Spectroscopy (EIS) measurements, it is clearly observed that the cathodic resistance considerably decreases when optimized synthesis parameters are used, obtaining a better performance for the Gd0.8Sr0.2Fe0.8Ga0.2O3 nanowires with an area specific resistance (ASR) value at 850 ∘C of 0.195 Ω cm2. [Copyright &y& Elsevier]

Abstract: Polycrystalline samples of La0.8Ca0.2Fe0.8Ni0.2O3−δ (LCFN) with perovskite type structure have been prepared by combustion, freeze drying, citrate-gel process and liquid mix method. The analysis of X-ray powder diffraction indicated that the samples were single phase and crystallized in an orthorhombic (space group, Pnma no. 62) structure. Transmission electron microscopy (TEM) analysis on the synthesized powder at 600°C by liquid mix method showed clusters of 150nm formed by nanoparticles of 20nm. Electrochemical performance of LCFN cathodes, which are used for intermediate temperature solid oxide fuel cells, were investigated. The polarization resistance was studied using two different electrolytes: Y-doped zirconia (YSZ) and Sm-doped ceria (SDC). The dc four-probe measurement exhibits a total electrical conductivity, over 100Scm−1 at T ≥600°C, pointing out that strontium can be substituted for the cheaper calcium cation without destroying the electrochemical properties. Experimental results indicate that nanoparticles have more advantages in terms of smaller particle size and better electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract: Well crystallized and homogeneous LiFePO4/C (LFPO) thin films have been grown by pulsed laser deposition (PLD). The targets were prepared by the sol–gel process at 600°C. The structure of the polycrystalline powders was analyzed with X-ray powder diffraction (XRD) data. The XRD patterns were indexed having a single phase olivine structure (Pnma). LFPO thin films have been deposited on three different substrates: aluminum (Al), stainless steel (SS) and silicon (Si) by pulsed laser deposition (PLD). The structure of the films was analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It is found that the crystallinity of the thin films depends on the substrate temperature which was set at 500°C. When annealed treatments were used, secondary phases were found, so, one step depositions at 500°C were made. Stainless steel is demonstrated to be the best choice to act as substrate for phosphate deposition. LiFePO4 thin films grown on stainless steel plates exhibited the presence of carbon, inducing a slight conductivity enhancement that makes these films promising candidates as one step produced cathodes in Li-ion microbatteries. [Copyright &y& Elsevier]

Abstract: Iron–cobalt-based perovskite oxides with general formula Ln0.7Sr0.3Fe0.8Co0.2O3−δ (where Ln=La, Pr and Gd) have been investigated for their application as intermediate-temperature cathodes in solid oxide fuel cells (SOFCs). Powdered samples of these materials were synthesized by a novel gel combustion process and then characterized by X-ray powder diffraction (XPD) and scanning electron microscopy (SEM). XPD patterns were satisfactorily indexed with an orthorhombic GdFeO3-type structure and, for all samples, a mean particle size of less than 1μm was estimated from the SEM data. Experimental single-chamber SOFCs using with these materials as cathodes and NiO–SDC (samaria-doped ceria) and SDC as anode and electrolyte, respectively, were evaluated at 600°C in a methane/oxygen mixtures. Peak power densities of 65.4, 48.7 and 46.2mWcm−2 were obtained for Ag|Ln0.7Sr0.3Fe0.8Co0.2O3−δ |SDC|NiO–SDC|Pt cells with Ln=Pr, La and Gd, respectively. The relatively high power density obtained for the Pr compound shows that it could be an interesting material for cathode of single-chamber SOFCs. [Copyright &y& Elsevier]

Abstract: Polycrystalline samples of La0.6Ca0.4Fe1−x Ni x O3 (x =0.1, 0.2, 0.3) (LCFN) are prepared by liquid mix method. The structure of the polycrystalline powders is analyzed with X-ray powder diffraction data. The XRD patterns are indexed as the orthoferrite similar to that of LaFeO3 having a single phase with orthorhombic perovskite structure (Pnma). The morphological characterization is performed by scanning electron microscopy (SEM) obtaining a mean particle size less than 300nm. Polarization resistance is studied using two different electrolytes: Y-stabilized zirconia (YSZ) and Sm-doped ceria (SDC). Electrochemical impedance spectroscopy (EIS) measurements of LCFN/YSZ/LCFN and LCFN/SDC/LCFN test cells are carried out. These electrochemical experiments are performed at equilibrium from 850°C to room temperature, under both zero dc current intensity and air. The best value of area specific resistance (ASR) obtained is 0.88Ωcm2, corresponding to the La0.6Ca0.4Fe0.9Ni0.1O3 material using SDC as electrolyte. The dc four-probe measurement indicates that La0.6Ca0.4Fe0.9Ni0.1O3 exhibits fairly high electrical conductivity, over 300Scm−1 at T >500°C. [Copyright &y& Elsevier]

Polycrystalline samples of Pr1− x Sr x Fe0.8Co0.2 O3− δ ( x=0.1, 0.2, 0.3) (PSFC) were prepared by the combustion synthesis route at 1200°C. The structure of the polycrystalline powders was analysed with X-ray powder diffraction data. The X-ray diffraction (XRD) patterns were indexed as the orthoferrite similar to that of PrFeO3 having a single-phase orthorhombic perovskite structure (Pbnm). Pr1− x Sr x Fe0.8Co0.2O3− δ ( x=0.1, 0.2, 0.3) films have been deposited on yttria-stabilized zirconia (YSZ) single-crystal substrates at 700°C by pulsed laser deposition (PLD) for application to thin film solid oxide fuel cell cathodes. The structure of the films was analysed by XRD, scanning electron microscopy (SEM) and atomic force microscopy (AFM). All films are polycrystalline with a marked texture and present pyramidal grains in the surface with different size distributions. Electrochemical impedance spectroscopy (EIS) measurements of PSFC/YSZ single crystal/PSFC test cells were conducted. The Pr0.7Sr0.3Fe0.8Co0.2O3− δ film at 850°C presents a lower area specific resistance (ASR) value, 1.65 Ω cm2, followed by the Pr0.8Sr0.2Fe0.8Co0.2O3− δ (2.29 Ω cm2 at 850°C) and the Pr0.9Sr0.1Fe0.8Co0.2O3− δ films (5.45 Ω cm2 at 850°C). [ABSTRACT FROM AUTHOR]

Electrolyte supported symmetric cells featuring La0.6Ca0.4Fe0.8Ni0.2O3 (LCFN) electrodes are studied by electrochemical impedance spectroscopy. The aim is to describe the polarization losses of this mixed ionic electronic conductor electrode at various cell operating conditions for cells sintered at different temperatures. An equivalent circuit describing the cathode polarization resistances was constructed from analyzing impedance spectra recorded at different oxygen partial pressures and temperatures. Favorable oxygen reduction reaction properties are demonstrated for the LCFN cell sintered at 750 °C with a polarization resistance of 0.05 Ω cm2 at an operating temperature of 800 °C in pure oxygen. [ABSTRACT FROM AUTHOR]

For Solid Oxide Fuel Cells (SOFCs) to become an economically attractive energy conversion technology, suitable materials and structures which enable operation at lower temperatures, while retaining high cell performance, must be developed. Recently, the perovskite-type La0.6Ca0.4Fe0.8Ni0.2O3 oxide has shown potential as an intermediate temperature SOFC cathode. An equivalent circuit describing the cathode polarization resistances was constructed from analyzing impedance spectra recorded at different temperatures in oxygen. A competitive electrode polarization resistance is reported for this oxygen electrode using a Ce0.8Gd0.2O1.9 electrolyte, determined by impedance spectroscopy studies of symmetrical cells sintered at 800 °C and 1000 °C. Scanning electron microscopy (SEM) studies of the symmetrical cells revealed the absence of any reaction layer between cathode and electrolyte, and a porous electrode microstructure even when sintered at a temperature of only 800 °C. The performance of this cathode shows favorable oxygen reduction reaction (ORR) properties potentially making it an excellent choice for IT-SOFC application. [ABSTRACT FROM AUTHOR]

Incorporation of amino acid capping molecules (alanine (Ala), methionine (Met), phenylalanine (Phe), tryptophan (Trp), tyrosine (Tyr), and valine (Val)) in their zwitterionic form into archetypal [Zr 6 (μ 3 -O) 4 (μ 3 -OH) 4 ] 12+ clusters creates supramolecular frameworks in which the assembly of these highly charged discrete units with chloride counterions provides a unique combination of porosity, chirality, and proton conductivity. The supramolecular frameworks assembled from these cluster entities (i.e., ZrAla , ZrMet , ZrPhe , ZrTrp , ZrTyr , and ZrVal ) are based on the counterbalancing of the cationic hexanuclear entities by chloride anions. The resulting structures provide porous structures (except ZrVal ) with variability of chemical and structural stability based on their supramolecular interactions. Among these compounds, ZrPhe and ZrVal remain stable due to the presence of a double chelation-like interaction involving four hydrogen bonds formed between a chloride anion, two ammonium groups, and two coordinated water molecules from two adjacent hexanuclear units. The presence of multiple acidic proton positions and strong hydrogen-bond donor/acceptor groups on the water channels gives rise to easy proton conduction pathways within the structures. In fact, ZrPhe and ZrVal , together with ZrTyr , exhibit high proton conductivity values with varying dependencies on the atmospheric humidity. Finally, the correlation between proton conduction and porosity is discussed.

Aqueous zinc-ion batteries (AZiBs) have emerged as a promising alternative to lithium-ion batteries as energy storage systems from renewable sources. Manganese hexacyanoferrate (MnHCF) is a Prussian Blue analogue that exhibits the ability to insert divalent ions such as Zn 2+ . However, in an aqueous environment, MnHCF presents weak structural stability and suffers from manganese dissolution. In this work, zinc doping is explored as a strategy to provide the structure with higher stability. Thus, through a simple and easy-to-implement approach, it has been possible to improve the stability and capacity retention of the cathode, although at the expense of reducing the specific capacity of the system. By correctly balancing the amount of zinc introduced into the MnHCF it is possible to reach a compromise in which the loss of capacity is not critical, while better cycling stability is obtained.

Metal-organic frameworks and supramolecular metal-organic frameworks (SMOFs) exhibit great potential for a broad range of applications taking advantage of the high surface area and pore sizes and tunable chemistry. In particular, metalloporphyrin-based MOFs and SMOFs are becoming of great importance in many fields due to the bioessential functions of these macrocycles that are being mimicked. On the other hand, during the last years, proton-conducting materials have aroused much interest, and those presenting high conductivity values are potential candidates to play a key role in some solid-state electrochemical devices such as batteries and fuel cells. In this way, using metalloporphyrins as building units we have obtained a new crystalline material with formula [H(bipy)] 2 [(MnTPPS)(H 2 O) 2 ]·2bipy·14H 2 O, where bipy is 4,4'-bipyidine and TPPS 4- is the meso -tetra(4-sulfonatephenyl) porphyrin. The crystal structure shows a zig-zag water chain along the [100] direction located between the sulfonate groups of the porphyrin. Taking into account those structural features, the compound was tested for proton conduction by complex electrochemical impedance spectroscopy (EIS). The as-obtained conductivity is 1 × 10 -2 S·cm -1 at 40 °C and 98% relative humidity, which is a remarkably high value.

With the aim of achieving carbon neutrality, new policies to promote electric vehicle (EV) deployment have been announced in various countries. As EV sales gain market-share, the demand for batteries is growing very rapidly, and this has raised concerns about the raw-material supply. Therefore, efficient and environmentally friendly recycling methods for lithium-ion batteries (LIBs) are mandatory to properly implement circular economy paradigms in this field. Hydrometallurgical recycling methods are characterized by their selectivity, high product purity as well as low energy consumption. In order to accomplish a close-loop recycling method, in this work we propose the use of a deep eutectic solvent (DES) and alginate hydrogels as leaching reagent and adsorbent, respectively, for their reusability, availability and biodegradability. The solubility and thermal stability of a choline chloride-ethylene glycol based DES (choline chloride: ethylene glycol = 1:2) were investigated, 180 °C being regarded as the temperature threshold for this DES, and reaching up to 1.12g Co L -1 solubility after 8 h leaching. Moreover, the DES can be reused after the eutectic state recreation with a performance over 80% with respect to the pristine DES. Calcium cross-linked sodium alginate hydrogels, which were immersed in ethylene glycol and dehydrated afterwards, were able to extract cobalt from the leachate with an efficiency of 92%. The aforementioned hydrogels can be reused after desorption and reach 91% of the performance of the pristine ones. The DES together with alginate hydrogel brings therefore a highly efficient and reusable close-loop recycling method., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

In recent years, much effort has been invested into developing multifunctional drug delivery systems to overcome the drawbacks of conventional carriers. Magnetic nanoparticles are not generally used as carriers but can be functionalised with several different biomolecules and their size can be tailored to present a hyperthermia response, allowing for the design of multifunctional systems which can be active in therapies. In this work, we have designed a drug carrier nanosystem based on Fe 3 O 4 nanoparticles with large heating power and 4-amino-2-pentylselenoquinazoline as an attached drug that exhibits oxidative properties and high selectivity against a variety of cancer malignant cells. For this propose, two samples composed of homogeneous Fe 3 O 4 nanoparticles (NPs) with different sizes, shapes, and magnetic properties have been synthesised and characterised. The surface modification of the prepared Fe 3 O 4 nanoparticles has been developed using copolymers composed of poly(ethylene-alt-maleic anhydride), dodecylamine, polyethylene glycol and the drug 4-amino-2-pentylselenoquinazoline. The obtained nanosystems were properly characterised. Their in vitro efficacy in colon cancer cells and as magnetic hyperthermia inductors was analysed, thereby leaving the door open for their potential application as multimodal agents.

This review focuses on the combination of metal-organic frameworks (MOFs) and ionic liquids (ILs) to obtain composite materials to be used as solid electrolytes in metal-ion battery applications. Benefiting from the controllable chemical composition, tunable pore structure and surface functionality, MOFs offer great opportunities for synthesizing high-performance electrolytes. Moreover, the encapsulation of ILs into porous materials can provide environmentally benign solid-state electrolytes for electrochemical devices. Due to the versatility of MOF-based materials, in this review we also explore their use as anodes and cathodes in Li- and Na-ion batteries. Finally, solid IL@MOF electrolytes and their implementation into Li and Na batteries have been analyzed, as well as the design and advanced manufacturing of solid IL@MOF electrolytes embedded on polymeric matrices., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Urgoiti-Rodriguez, Vaquero-Vílchez, Mirandona-Olaeta, Fernández de Luis, Goikolea, Costa, Lanceros-Mendez, Fidalgo-Marijuan and Ruiz de Larramendi.)

Aprotic metal-O 2 batteries have attracted the interest of the research community due to their high theoretical energy density that target them as potential energy storage systems for automotive applications. At present, these devices show various practical problems, which hinder the attainment of the high theoretical energy densities. Among the main limitations, we can highlight the irreversible parasitic reactions that lead to premature death of the battery. The degradation processes, mainly related to the electrolyte, lead to the formation of secondary products that accumulate throughout the cycling in the air electrode. This accumulation of predominantly insulating products results in the blocking of active sites, promoting less efficiency in system performance. Recently, it has been discovered that the superoxide intermediate radical anion is involved in the generation of the reactive oxygen singlet species ( 1 O 2 ) in metal-O 2 batteries. The presence of singlet oxygen is intimately linked with electrolyte degradation processes and with carbon-electrode corrosion reactions. This review analyzes the nature of singlet oxygen, while clarifying its toxic role in metal-O 2 batteries. Besides, the main mechanisms of deactivation of singlet oxygen are presented, trying to inspire the research community in the development of new molecules capable of mitigating the harmful effects related to this highly reactive species., (Copyright © 2020 Ruiz de Larramendi and Ortiz-Vitoriano.)

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl 4 ] (trimim: 1,2,3-trimethylimidazolium) was synthetized and studied with structural and physico-chemical characterization. Variable-temperature synchrotron X-ray powder diffraction (SXPD) from 100 to 400 K revealed two structural transitions at 200 and 300 K. Three different crystal structures were determined combining single crystal X-ray diffraction (SCXD), neutron powder diffraction (NPD), and SXPD. From 100 to 200 K, the compound exhibits a monoclinic crystal structure with space group P 2 1 / c . At 200 K, the former crystal system and space group are retained, but a disorder in the organic cations is introduced. Above 300 K, the structure transits to the orthorhombic space group Pbcn , retaining the crystallinity up to 400 K. The study of the thermal expansion process in this temperature range showed anisotropically evolving cell parameters with an axial negative thermal expansion. Such an induction occurs immediately after the crystal phase transition due to the translational and reorientational dynamic displacements of the imidazolium cation within the crystal building. Electrochemical impedance spectroscopy (EIS) demonstrated that this motion implies a high and stable solid-state ionic conduction (range from 4 × 10 -6 S cm -1 at room temperature to 5.5 × 10 -5 S cm -1 at 400 K). In addition, magnetization and heat capacity measurements proved the presence of a three-dimensional antiferromagnetic ordering below 3 K. The magnetic structure, determined by neutron powder diffraction, corresponds to ferromagnetic chains along the a -axis, which are antiferromagnetically coupled to the nearest neighboring chains through an intricate network of superexchange pathways, in agreement with the magnetometry measurements., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

The depletion of fossil fuels, the rapid evolution of the global economy, and high living standards require the development of new energy-storage systems that can meet the needs of the world's population. Metal-oxygen batteries (M=Li, Na) arise, therefore, as promising alternatives to widely used lithium-ion batteries, due to their high theoretical energy density, which approaches that of gasoline. Although significant progress has been made in recent years, there are still several challenges to overcome to reach the final commercialization of this technology. One of the most limiting and challenging factors is the development of bifunctional cathodes towards oxygen reduction and evolution reactions. In this sense, graphene, which is very promising and tunable, has been widely explored by the research community as a key material for this technology. Herein, a wide literature overview is presented and analyzed with the aim of guiding future research in this field., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

With the aim of studying the influence of synthesis parameters in structural and magnetic properties of cobalt-doped magnetite nanoparticles, Fe 3- x Co x O₄ (0 < x < 0.15) samples were synthetized by thermal decomposition method at different reaction times (30-120 min). The Co ferrite nanoparticles are monodisperse with diameters between 6 and 11 nm and morphologies depending on reaction times, varying from spheric, cuboctahedral, to cubic. Chemical analysis and X-ray diffraction were used to confirm the composition, high crystallinity, and pure-phase structure. The investigation of the magnetic properties, both magnetization and electronic magnetic resonance, has led the conditions to improve the magnetic response of doped nanoparticles. Magnetization values of 86 emu·g -1 at room temperature (R.T.) have been obtained for the sample with the highest Co content and the highest reflux time. Magnetic characterization also displays a dependence of the magnetic anisotropy constant with the varying cobalt content., Competing Interests: The authors declare no conflict of interest.

A new route to enhance the performance of Na-O 2 cells is demonstrated. Redox mediators (such as ethyl viologen) are shown to facilitate the discharge reaction, producing an increased capacity (due to suppressed electrode passivation), higher discharge potential (due to faster kinetics) and stable cycling.