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Hydrogen can be used to sustain a revolutionary energy system, capable of integrating renewable sources and free from greenhouse gas emissions, in the perspective to mitigate global warming. Fuel cells and electrolyzers are the cornerstone of this new clean energy system, that is currently under research, development and implementation. [ABSTRACT FROM AUTHOR]

The article focuses on carbon nitride-based electrocatalysts for application in low-temperature fuel cells (FCs). Topics discussed include low-temperature fuel cells such as proton exchange membrane fuel cells (PEMFCs) and anion-exchange membrane fuel cells (AEMFCs), requirement of oxygen reduction reaction (ORR) electrocatalysts (ECs) to minimize cathode polarization losses and three dimensional (3D)-crosslinked hybrid macromolecular precursors.

Recent advancements in Vanadium Redox Flow Batteries (VRFBs) assert that their performance degradation and lack of charge retention is generally ascribed to the crossover of Vanadium species of the electrolytes through the Ion Exchange Membrane (IEM). In this report, a comprehensive electrochemical formalism is proposed to shed light on the role played by the equilibria and redox processes of the active Vanadium complexes in electrolytes in the modulation of the electrical behavior of an operating VRFB. This target is achieved by adopting the strategy to consider: a) the Vanadium species with the same oxidation state as a single ensemble of species; b) the redox processes as bridging events between the different ensembles of Vanadium species; and c) the correlations existing between chemical processes and the electrochemical status of a VRFB both in terms of potential and of self-discharge features. The developed formalism reveals the role played by the complex Vanadium coordination chemistry on the electrochemical performance of a VRFB. In detail, under Open Circuit Voltage (OCV) studies, VOH2+/V2+ and H 2 VO 4 −/VO2+ redox couples contribute negatively to the capacity retention of the device. During the charging process, VOH2+/V2+ and H 2 VO 4 −/VO2+ equilibria concur potentially for a decrease of the overall current density by up to 22% and 4.7%, respectively. Taken all together, the analyzed equilibria and the redox processes here proposed are not negligible in modulating the possible electrochemical loss of performance of a VRFB. Thus, these outcomes offer a different scenario to the widely accepted theory which considers to the crossover of active species through the ion-conducting membranes as the only one phenomenon responsible for the performance drop of these devices. Therefore, results here reported: (a) open the door for a systematic understanding of unforeseen phenomena which are potentially responsible for modulating the electrochemical performance loss of a VRFB; and (b) are a quantitative example of how to rationalize the behavior of a RFB, which is based on a complex chemistry. Finally, results shed light on a new scenario of phenomena that is necessary to master, in order to manage the operation of a VRFB and to improve its long-term stability and charge retention ability, particularly under rest conditions. [ABSTRACT FROM AUTHOR]

The thermal, mechanical, and electric properties of hybrid membranes based on Nafion that contain a [(ZrO2)·(Ta2O5)0.119] "core–shell" nanofiller are elucidated. DSC investigations reveal the presence of four endothermic transitions between 50 and 300 °C. The DMA results indicate improved mechanical stability of the hybrid materials. The DSC and DMA results are consistent with our previous suggestion of dynamic R-SO3H…[ZrTa] cross-links in the material. These increase the thermal stability of the -SO3H groups and the temperature of thermal relaxation events occurring in hydrophobic domains of Nafion. The broadband electrical spectroscopic analysis reveals two electric relaxations associated with the material's interfacial (σIP) and bulk proton conductivities (σEP). The wet [Nafion/(ZrTa)1.042] membrane has a conductivity of 7.0 × 10-2 S cm-1 at 115 °C, while Nafion has a conductivity of 3.3 × 10-2 S cm-1 at the same temperature and humidification conditions. σEP shows VTF behavior, suggesting that the long-range conductivity is closely related to the segmental motion of the Nafion host matrix. Long-range conduction (σEP) occurs when the dynamics of the fluorocarbon matrix induces contact between different delocalization bodies (DB), which results in proton exchange processes between these DBs. [ABSTRACT FROM AUTHOR]

Abstract: Two classes of hybrid inorganic–organic proton-conducting membranes consisting of Nafion and either [(ZrO2)·(HfO2)0.25] or [(SiO2)·(HfO2)0.28] nanofiller are investigated to elucidate their relaxations and conductivity mechanism and are labeled [Nafion/(ZrHf) x ] and [Nafion/(SiHf) x ], respectively. The membranes are studied by dynamic mechanic analysis (DMA) and broadband electric spectroscopy (BES). The latter technique allows a determination of the direct current ionic conductivity (σ DC) and the proton diffusion coefficient . Pulse-field-gradient spin-echo nuclear magnetic resonance experiments (PFGSE-NMR) are carried out to determine the water self-diffusion coefficients . and are correlated to obtain insight on the conductivity mechanism of the proposed materials. Results indicate that the nanofiller particles play a major role in the proton conduction mechanism of the proposed materials. It is demonstrated that the basic [(ZrO2)·(HfO2)0.25] nanoparticles form Nafion–nanofiller dynamic cross-links with high ionic character. These cross-links improve the mechanical properties and enhance the overall proton conductivity of the membranes at low humidification levels owing to an efficient delocalization of the protons. In [Nafion/(SiHf) x ] membranes, the dynamic cross-links occur due to dipole–dipole interactions between the side groups of the Nafion host polymer and the quasi-neutral [(SiO2)·(HfO2)0.28] nanoparticles. These cross-links significantly reduce the delocalization of the protons, which decreases the overall conductivity of materials. [Copyright &y& Elsevier]

Abstract: This work reports the preparation, characterization and test in a single fuel cell of two families of hybrid inorganic-organic proton-conducting membranes, each based on Nafion and a different “core-shell” nanofiller. Nanofillers, based on either a ZrO2 “core” covered with a HfO2 “shell” (ZrHf) or a HfO2 “core” solvated by a “shell” of SiO2 nanoparticles (SiHf), are considered. The two families of membranes are labelled [Nafion/(ZrHf) x ] and [Nafion/(SiHf) x ], respectively. The morphology of the nanofillers is investigated with high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX) and electron diffraction (ED) measurements. The mass fractions of nanofiller x used for both families are 0.05, 0.10 or 0.15. The proton exchange capacity (PEC) and the water uptake (WU) of the hybrid membranes are determined. The thermal stability is investigated by high-resolution thermogravimetric measurements (TGA). Each membrane is used in the fabrication of a membrane-electrode assembly (MEA) that is tested in single-cell configuration under operating conditions. The polarization curves are determined by varying the activity of the water vapour (aH2O) and the back pressure of the reagent streams. A coherent model is proposed to correlate the water uptake and proton conduction of the hybrid membranes with the microscopic interactions between the Nafion host polymer and the particles of the different “core–shell” nanofillers. [Copyright &y& Elsevier]

Abstract: In this report, three hybrid inorganic-organic proton-conducting membranes based on a novel fluorinated titania labeled TiO2F dispersed in Nafion were prepared. The mass fraction of TiO2F nanofiller ranged between 0.05 and 0.15. The water uptake and the proton exchange capacity of the membranes were determined; the membranes were further characterized by TG, DMA and FT-IR ATR investigations. Finally, the hybrid membranes were used in the fabrication of membrane-electrode assemblies (MEAs), which were tested in operating conditions as a function of the back pressure and of the hydration degree of the reagents streams. It was demonstrated that, with respect to pristine recast Nafion, at 25%RH the MEA fabricated with the membrane including a mass fraction of TiO2F equal to 0.10 yielded a higher maximum power density (0.206 W cm−2 vs. 0.121 W cm−2). Finally, it was proposed a coherent structural model of this family of hybrid membranes accounting for both the properties determined from “ex-situ” characterizations and for the performance obtained from measurements in a single fuel cell in operating conditions. [Copyright &y& Elsevier]

Abstract: Many papers have focused on the thermal properties, conductivity and fuel cell performance of sulfonated poly(ether ether ketone) (SPEEK) membranes, but the electrical properties have not been extensively studied. In this work, the electric properties of SPEEK electrolytes are studied with broadband electric spectroscopy to elucidate the relationship between the degree of sulfonation and the conductivity and to explore the mechanism of long-range conductivity. SPEEK membranes exhibit two polarization phenomena that contribute to the overall conductivity: “bulk” and interfacial conductivities. The “bulk” conductivity increases with increasing degrees of sulfonation due to an increase in the concentration of charge carriers and a higher hydrophilicity that allows increased water uptake. The interfacial conductivity is the result of the accumulation of charge at the interfacial regions between the hydrophobic and hydrophilic domains of the SPEEK membranes. The bulk and interfacial conductivities can be divided into two temperature regimes: one at temperatures below 75°C that exhibits Arrhenius behaviour and the other at temperatures above 75°C that follows a Vogel–Tamman–Fulcher (VTF) trend. In the Arrhenius region, proton transport occurs primarily via a Grotthus-like mechanism where protons move between water molecules and acid groups. In the VTF region, segmental motion is critical in the long-range proton conduction process as the mean hopping distance increases along with the temperature due to loss of water. [Copyright &y& Elsevier]

Abstract: This report describes the preparation of two Pd-based carbon nitride electrocatalysts for the oxygen reduction reaction (ORR) for application in polymer electrolyte membrane fuel cells (PEMFCs). The electrocatalysts consist of multi-metallic active sites supported on a graphite-like carbon nitride (CN) matrix with a N content exceeding 13wt%. The electrochemical performance is investigated by cyclic voltammetry with the thin-film rotating disk electrode method (CV-TF-RDE) and evaluated in a single membrane electrode assembly (MEA) PEMFC. The correlation of the structural information to functional properties allows to propose a reaction mechanism and to identify the most desirable features to achieve in a CN electrocatalyst in order to obtain desired electrochemical performance in catalysis of ORR. It is established also that the CN support improves the tolerance towards the catalyst corrosion under oxidizing conditions and thus improves the catalyst durability. The stoichiometry and the morphology of Pd-based CN electrocatalysts play a crucial role in the modulation of the tolerance towards common ORR poisons such as chlorine anions and methanol. Finally, the performance of the Pd-based CN electrocatalysts in a single MEA PEMFC proved promising. [Copyright &y& Elsevier]

Abstract: This report describes a new family of bimetal carbon nitride (CN) electrocatalysts for the oxygen reduction reaction (ORR) for application in polymer electrolyte membrane fuel cells (PEMFCs). The materials, which bear active sites based on Pt and Rh, are prepared with a three-step protocol consisting of: (1) the synthesis of a homogeneous zeolitic inorganic–organic polymer electrolyte (Z-IOPE) precursor; (2) the pyrolysis of the precursor at a temperature T f =400, 500, 600, 700 or 900°C; (3) the activation, yielding the final product. It is found that T f has a major effect on the structure and the electrochemical properties of these electrocatalysts, as determined from a wide array of independent characterization techniques including: high-resolution thermogravimetry (HR-TGA); Fourier-transform medium infrared (FT-MIR), Fourier-transform far infrared (FT-FIR) and confocal micro-Raman spectroscopies; powder X-ray diffraction (powder XRD); X-ray photoelectron spectroscopy (XPS); and electrochemical investigations carried out with the cyclic voltammetry thin-film rotating disk electrode (CV-TF-RDE) method. All the information is integrated to propose a comprehensive model correlating the effect of T f on the structure of the materials with the corresponding electrochemical performance. The best results in the ORR are obtained with materials prepared at 600≤ T f ≤700°C. These systems present the optimal compromise between the size of the metal-rich nanoparticles, the degree of graphitization of the carbon nitride support and the concentration of ligands blocking the active sites. The best Pt-Rh electrocatalysts exhibit an ORR activity very similar to the Pt/C reference. In addition, the peculiar structure of the proposed materials, which are characterized by active sites supported on the carbon nitride bulky materials, results in a better tolerance toward typical contaminants in the ORR process such as chloride anions with respect to the Pt/C reference. [Copyright &y& Elsevier]

Abstract: The dielectric and conductivity study of two series of five three-dimensional hybrid inorganic–organic networks as polymer electrolytes (3D-HION-APEs), with formula {Al[O(CH2CH2O)8.7] ρ /(LiClO4) z } n (1.86≤ ρ ≤2.24, 0≤ z ≤1.06) and {Zr[O(CH2CH2O)8.7] ρ /(LiClO4) z } n (1.81≤ ρ ≤1.99, 0≤ z ≤0.91) is presented. The real and imaginary components of the complex dielectric permittivity spectra ɛ * and conductivity spectra σ * are measured between −60°C and 80°C. Spectral analysis points out that the conductivity mechanism is determined by two dielectric relaxation events, α and β. The relaxation β occurs at higher frequencies than α, and is attributed to the segmental motion with characteristic frequency f seg. The relaxation α is attributed to the ionic motion with characteristic frequency f ion. The profiles of the direct conductivity σ dc and the frequencies f ion and f seg vs. the reciprocal temperature exhibit a Vögel–Tamman–Fülcher (VTF) behavior. The study of the activation energies of the dielectric relaxations α and β allows to determine their relative contribution to the direct conductivity σ dc at lower and higher temperatures. The dependence of the VTF parameters vs. the mole-to-mole ratios n Li/n O and n Li/n M (M=Zr, Al) in combination with previous equivalent conductivity studies, allows to identify the role of the ionic species and the metal nodes present in the polymer structure at various salt concentrations. The correlation between the diffusion coefficient D and the relaxation frequencies f seg and f ion of the 3D-HION-APEs is investigated. [Copyright &y& Elsevier]

Abstract: Polymer electrolytes, generally, are all those materials where a supramolecular system is doped with ions and presents a significant conductivity. Following the 12th and most recent International Symposium of Polymer Electrolytes (ISPE-12), this historical and critical review summarizes the main developments in the fundamental science and applications of this family of materials since their establishment approximately 40 years ago. The history of polymer electrolytes is briefly outlined and the main families are reviewed in the framework of a tentative classification scheme. The applications of polymer electrolytes are discussed, highlighting the role of the electrolyte materials and reporting the most widely accepted performance and durability benchmarks in the various fields. Finally, a statistical analysis of the available scientific literature is presented to identify the most relevant current trends and future possibilities in the diversification and growth of worldwide research on this topic. [Copyright &y& Elsevier]

Conformational changes in polymer films exposed to high-pressure CO2have been investigated with Fourier transform infrared (FT-IR) spectroscopy. The experimental setup, based on a custom-made stainless steel optical cell with CaF2windows, allows measurements in a CO2environment for pressures up to 6 MPa, in a temperature range from 293 to 353 K and in the mid-infrared (1000–4000 cm–1). Poly(methyl methacrylate) (PMMA), a polymer with a side group (C-type), was studied to monitor the spectral changes as a function of CO2pressure and was compared to poly(d,l-lactic-co-glycolic acid) (PLGA), a polymer without a side group (B-type). By monitoring the characteristic carbonyl bands, conformational changes that occur due to molecular interactions between the high-pressure CO2and the polymers were explored at a constant pressurization rate (0.02 MPa/min) and temperature. Spectral changes are observed only for PMMA, where the vibrational band at 1680 cm–1disappears with increasing pressure. The spectra of PLGA do not show any significant change in the presence of high pressure CO2in the investigated range. The behavior of the absorbance peak as a function of pressure and temperature highlights the presence of dynamic cross-links (DCs) between the side groups of PMMA films obtained by solvent casting below the glass transition temperature of the polymer. The spectral features are correlated using a model that accounts for CO2diffusion and the relaxation kinetics of the polymer chains in the thin film. The disappearance of the vibrational band attributed to the DCs for PMMA is related to the glass transition temperature, and a retrograde vitrification phenomenon is observed. This approach can be considered a useful alternative to magnetic suspended balance for the study of polymer–gas systems. [ABSTRACT FROM AUTHOR]

Abstract: In this report, a new nanofiller consisting of silica “cores” bearing fluoroalkyl surface functionalities is synthesized and adopted in the preparation of a series of hybrid inorganic–organic proton conducting membranes based on Nafion. The hybrid materials are obtained by a solvent-casting procedure and include between 0 and 10wt.% of nanofiller. The resulting systems are extensively characterized by Thermogravimetry (TG), Modulated Differential Scanning Calorimetry (MDSC) and Dynamic Mechanical Analysis (DMA), showing that the hybrid materials are stable up to 240°C and that their overall thermal and mechanical properties are affected both by the polar groups on the surface of the silica “cores” and by the fluoroalkyl surface functionalities of the nanofiller. The electric properties of the hybrid materials are investigated by broadband dielectric spectroscopy (BDS). It is shown that proton conductivity of the materials is not compromised by the lower water uptake arising from the hydrophobic character of the nanofiller. With respect to a pristine Nafion recast membrane, the hybrid material characterized by 5wt.% of nanofiller, [Nafion/(Si80F)0.7], shows the highest conductivity in all the investigated temperature range (5≤ T ≤155°C). Indeed, [Nafion/(Si80F)0.7] features the lowest water uptake and presents a conductivity of 0.083Scm−1 at 135°C. This result is consistent with the good performance of the membrane in single fuel cell tests. [ABSTRACT FROM AUTHOR]

Abstract: This report describes the development and the optimization of new synthesis routes yielding electrocatalysts for the oxygen reduction reaction (ORR) aimed at application in proton exchange membrane fuel cells (PEMFCs). The preparation protocols consist in the synthesis of two groups of hybrid inorganic–organic precursors, characterized by a different concentration of nitrogen, which subsequently undergo a high-temperature pyrolysis in inert atmosphere, washing and activation. The resulting materials show a well-controlled stoichiometry. The nitrogen incorporated in the support transforms the matrix into a supramolecular ligand, and stabilizes the electrocatalyst by coordinating the active metal clusters. The latter are composed of an “active metal” such as Pt or Pd, combined with one or more “co-catalyst” elements such as Au, Fe, Co and Ni. An extensive characterization of the carbon nitride electrocatalysts under the chemical, structural, morphological and electrochemical points of view is described, together with their use in membrane electrode assemblies (MEAs) tested in single fuel cells under operative conditions. Results indicated that the best electrocatalysts are those characterized by a “core–shell” morphology. These systems consist of metal carbon nitride materials with a low concentration of nitrogen (shell) supported on electronically conductive graphite nanoparticles (core). Promising results were obtained both in terms of ORR overpotential (η) and of mass activity (A m). Indeed, η resulted up to ∼30mV lower with respect to reference Pt-based systems, and an A m equal to 0.3–0.4g of Pd or Pt to achieve 1kW was reached. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFCs) constitute nowadays a promising alternative to lithium ion batteries for powering portable devices. The effective design of power-management units for interfacing DMFCs requires accurate models able to account for variable-load conditions and fuel consumption. A dynamic nonlinear circuit model for passive methanol fuel cells is presented in this paper. The model takes into account mass transport, current generation, electronic and protonic conduction, methanol adsorption, and electrochemical kinetics. Adsorption and oxidation rates, which mostly affect the cell dynamics, are modeled by a detailed two-step reaction mechanism. The fully coupled multiphysics equivalent circuit is solved by assembling first-order differential equations into a nonlinear state-variable system in order to simulate the electrical evolution of the fuel cell from its initial conditions. The fuel-cell discharge and methanol consumption are computed by combining mass-transport and conservation equations. As a result, the runtime of a DMFC can be predicted from the current load and the initial methanol concentration. [ABSTRACT FROM AUTHOR]

Abstract: In this report are presented the preparation and the characterization of six nanocomposite membranes of formula with in the range 0–2.988. These materials are based on Nafion and [(TiO2)·(WO3)0.148] nanofiller. The effect of [(TiO2)·(WO3)0.148] nanopowders on the structural, thermal, mechanical and electrical properties of membranes was studied. The water uptake (WU) value of materials was lower than that of pristine Nafion and was correlated with . The thermal transitions were investigated by modulated differential scanning calorimetry (MDSC). The mechanical parameters and relaxation processes on temperature were studied by dynamical mechanical analyses (DMA). The FT-IR ATR and μ-Raman vibrational investigations allowed to determine the structure of the hydrophobic polytetrafluoroethylene (PTFE) domains of Nafion and the interactions Nafion–[(TiO2)·(WO3)0.148] and Nafion–[H2O] in bulk materials. The analysis of complex conductivity plots were evaluated in the 10−2 Hz–10MHz and 5–155°C regions. Results indicated that the conductivity of nanocomposite membrane, with , at 135°C, is 5.0×10−2 Scm−1, while its stability range of conductivity (SRC) extends up to 135°C. [Copyright &y& Elsevier]

Abstract: This paper reports the preparation of two families of platinum-free carbon nitride electrocatalysts with general formula PdCoX-CNy. These materials were synthesized through innovative protocols which permitted to control the stoichiometry of the active sites and the concentration of nitrogen in the carbon nitride support. The electrocatalysts were extensively characterized in terms of chemical, thermal, morphological and electrochemical points of view. The materials characterized by a nitrogen concentration >15%, with respect to the platinum reference exhibited an improved tolerance toward the thermal degradation under oxidizing conditions. Electrochemical measurements, performed with the cyclic voltammetry-thin film rotating disk electrode method (CV-TF-RDE), showed that the oxygen reduction reaction (ORR) of proposed materials occurs through a mechanism similar to that of the platinum reference both in the high- and in the low-potential regimes. In addition, results demonstrated that, with respect to the platinum reference, the overpotential in the ORR of proposed materials increases as the N concentration in the support is raised. The most important figures of merit accounting for the performance of the electrocatalysts were determined by assembling the materials in single PEMFCs which were tested under operative conditions. Finally, it was determined that selected electrocatalysts required 0.69g of palladium to produce 1kW of power; in the same conditions the reference MEA needed 1.12g of platinum. [Copyright &y& Elsevier]

Abstract: In this paper the preparation of a new bimetal electrocatalyst for the oxygen reduction reaction (ORR), which is one of the most important bottlenecks in the operation of polymer electrolyte membrane fuel cells (PEMFCs), is described. This material was synthesized through a pyrolysis process of a zeolitic inorganic–organic polymer electrolyte (Z-IOPE-like) precursor, followed by suitable washing and activation procedures of the product. The electrocatalyst, whose active sites consist of platinum and rhodium, was: (a) extensively characterized from the chemical, structural, morphological and electrochemical points of view and (b) used to prepare a membrane-electrode assembly (MEA) which was tested under operative conditions in a single-cell configuration. It was observed that, with respect to a reference material based on supported platinum, rhodium did not compromise the performance of the electrocatalyst in the ORR. This behaviour was interpreted in the framework of a general model concerning the enhancement of ORR performance in bimetal systems supported on carbon nitrides. Finally, the material shows a slightly better tolerance toward a few common contaminants for the ORR such as methanol and chloride anions, typical of direct methanol fuel cells (DMFCs) and vehicular applications, respectively. [Copyright &y& Elsevier]

Abstract: In this report, we are presenting studies of the effect of M x O y nanopowders on the thermal, mechanical and electrical properties of [Nafion/(M x O y ) n ] membranes with M=Ti, Zr, Hf, Ta and W and n =5wt%. Five homogeneous membranes with thicknesses ranging from 170 to 350μm were studied. The thermal transitions characterizing [Nafion/(M x O y ) n ] materials were investigated by modulated differential scanning calorimetry (MDSC). The mechanical parameters and relaxation processes were studied on temperature by dynamical mechanical analyses (DMA). Broadband dielectric spectroscopy (BDS) was used to study the conductivity mechanism and dielectric relaxation events in bulk materials. DMA investigations showed two distinct relaxation events. The first relaxation phenomenon, detected at about 19°C, was attributed to the mechanical β-relaxation mode of Nafion. The second event, revealed in the temperature range 100–135°C, was assigned to the mechanical α-relaxation mode of Nafion. The electric response of membranes was studied by BDS measurements in the frequency and temperature range respectively of 40Hz–10MHz and 5–135°C. Real and imaginary components of permittivity (ɛ*(ω)= ɛ′ (ω)−iɛ″(ω)) and conductivity spectra (σ*(ω)= σ′(ω)+iσ″(ω)) were analyzed. Conductivity spectra allowed us to accurately determine the σ dc of membranes at 100% RH as a function of T. Two relaxation peaks were detected in the ɛ*(ω) profiles. The low frequency relaxation event was attributed to the α-relaxation mode of fluorocarbon chains of Nafion. The high frequency relaxation peak corresponds to the β-relaxation of acid side groups. The results allowed us to conclude that M x O y influences: (a) the relaxations of both the hydrophobic and the hydrophilic domains of Nafion polymer host; (b) the thermal stability range of conductivity (SRC) and the σ dc of membranes. In conclusion, nanofillers affect the macromolecular dynamics of Nafion-based polymer host owing to the formation of dynamic cross-links, R–SO3H⋯M x O y ⋯HSO3–R, in hydrophilic polar cages. The membranes doped with HfO2 and WO3 oxoclusters present a stability range of conductivity of 5°C≤ T ≤135°C and give rise to σ dc values of respectively 2.8×10−2 and 2.5×10−2 Scm−1 at 135°C and 100% RH. These latter conductivity values make the nanocomposite membranes based on HfO2 and WO3 oxoclusters very promising materials for the application in polymer electrolyte fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). [Copyright &y& Elsevier]

Abstract: In this work, two new bimetallic carbon nitride electrocatalysts, based on platinum and either nickel or iron, are tested in a single-cell PEMFC. The membrane electrode assembly (MEA) is prepared using the proposed electrocatalysts at the cathodic side and two different reference materials at the anode. MEA performance is extensively tested in both kinetically controlled (V>0.9V) and “operative” (V≈0.65V) regimes, with both air and pure oxygen as oxidants. Electrochemical information on the performance of cathodic electrodes is also obtained by carrying out measurements with the “driven cell” method. The proposed materials show very high activity in both operating regimes and, with respect to the reference electrocatalysts, exhibit a lower overpotential (∼40mV) towards the ORR. Interestingly, only a lower mass of platinum is necessary to obtain the same electrical power (up to 0.61gPt kW−1 vs. 1.1gPt kW−1 of the reference MEA), leading to the possibility of producing cheaper MEAs. The electrochemical surface area of the proposed materials is larger than that of reference electrocatalysts. Lastly, the active sites of these bimetallic carbon nitride electrocatalysts are much less susceptible to CO poisoning. [Copyright &y& Elsevier]

Abstract: In this report is described the preparation of six nanocomposite membranes of formula with ranging from 0 to 1.79 based on Nafion® and [(ZrO2)·(SiO2)0.67] nanofiller. Morphology investigations carried out by SEM measurements indicate that the composition of membranes is asymmetric. Indeed, with respect to the direction of the films after casting procedure, the top side (A-side) and bottom side (B-side) present a different nanofiller concentration. The concentration of nanofiller increases gradually from A to B side. The membranes present thicknesses ranging from 170 to 350nm and are studied by FT-IR ATR and micro-Raman measurements. The vibrational investigations permit us to reveal that: (a) the hydrophobic polytetrafluoroethylene (PTFE) domains of Nafion® are composed of a mixture of polymer chains with 157 and 103 helical conformations; (b) the concentration of chains with 103 helical conformation depends on the nanofiller concentration and is much higher in side A; (c) six different water domains are present in bulk membranes which are singled out as I, II, II, III, III and IV; (d) water uptake of membranes is correlated to the conformational transition 103 →157 of PTFE chains occurring in hydrophobic domains of Nafion®. The conductivity of was determined by analyzing the complex conductivity plots measured in the frequency and temperature range of 10−2 Hz–10MHz and 5–155°C, respectively. Interestingly, the nanocomposite membranes with and 0.534 showed values of conductivity of 4.3×10−2 Scm−1 at 135°C and of 3.5×10−2 Scm−1 at 115°C, respectively. [Copyright &y& Elsevier]

Abstract: In this paper is described the preparation of new platinum-free Pd-Co carbon-nitride electrocatalysts (Pd-Co-CNs) for application in low-temperature fuel cells. Two groups of materials with formula K n [Pd x Co y C z N l H m ] were synthesized, which are grouped in two ensembles: the first is characterized by a molar ratio y/x >1 (I), and the second by y/x <1 (II). K n [Pd x Co y C z N l H m ] materials were prepared through a two-step synthesis protocol. The effect of the Pd/Co molar ratio and of the temperature of the thermal treatments on the structure and properties of the products were studied extensively by thermogravimetry, scanning electron microscopy, and vibrational (FT-IR and micro-Raman) and XPS spectroscopy. Vibrational studies revealed that I and II systems consist of two polymorphs of α- and graphitic-like carbon-nitride nanomaterials. The electrochemical activity towards the oxygen reduction reaction (ORR) and the hydrogen oxidation reaction (HOR) was measured by cyclic voltammetry measurements with thin-film rotating disk electrode (CV-TF-RDE). The electrochemical performance of Pd-Co-CNs of group I obtained at t f ≥700°C resulted higher than that measured for a platinum-based commercial electrocatalyst in terms of both the activity towards the ORR and the HOR and of the resistance towards the poisoning effect of methanol towards the ORR. [Copyright &y& Elsevier]

This paper describes the effect of nanopowders acting as fillers on the structure and properties of [Nafion/(MxOy)n] membranes with n = 5 wt.%. The films were prepared by a solvent casting procedure using MxOy oxoclusters (M = Ti, Zr, Hf, Ta and W) and Nafion. Five new homogeneous membranes were prepared with thicknesses ranging from 170 to 350 μm. The membranes were characterized by means of thermal analyses carried out by thermogravimetry (TG), morphological measurements by scanning electron microscopy (ESEM) and vibrational spectroscopy by FT-IR ATR, FT-Raman measurements. Vibrational investigations allowed us to obtain information on: (a) the network structure and the conformation of fluorocarbon hydrophobic domains of the Nafion host polymer, (b) the MxOy⋯HSO3R interactions occurring in ionic polar cages of membranes and (c) the various water domains present in the hydrophilic polar cages of membranes. TG allowed us to determine that the membranes are thermally stable up to about 170 °C.In conclusion, it was disclosed that: (a) the hydrophobic Nafion polymer host domains consist of a blend of PTFE chains with helical conformations 103 and 157 and (b) the fraction of each fluorocarbon helical conformation is modulated by the type of nano-fillers and the dynamic cross-links RSO3H⋯MxOy⋯HSO3R which occur in hydrophilic polar cages of membranes. In hydrophobic domains of Nafion, the highest percentage of fluorocarbon chains with helical conformation 103 is observed for [Nafion/(HfO2)n] composite membrane, ρ (%) = 16. [Copyright &y& Elsevier]

Abstract: This contribution is focused on the conductivity study and the protonic transfer investigation of two new siloxanic membranes. The conductivity of the systems has been studied within the temperature range 5°C≤ T ≤145°C, both for pristine and hydrated membranes. Membrane A has been hydrated up to 33.12% in weight, while in B up to 27.76%. The conductivity of these membranes has shown a temperature dependence of the Arrhenius type variable in the interval 1.6×10−4 ≤ σ A ≤2.3×10−3 Scm−1 and 1.3×10−5 ≤ σ B ≤2.9×10−4 Scm−1, respectively, for A and B. In particular, conductivities of 2×10−3 Scm−1 (A) and of 2×10−4 Scm−1 (B) at 125°C were observed. The conductivity mechanism was investigated by using broad band electrical spectroscopy in the region between 40Hz and 10MHz. This study, for both the materials has shown the presence at low frequencies (102 ≤ f β ≤104 Hz) of β relaxations related to the sulphonic side chain dynamics. The activation energy measured for this molecular dynamics is about ≅30kJmol−1 and corresponds to the typical interaction energy associated with hydrogen bonding. Furthermore, it was observed that the activation energies determined from the conductivity measurements are 12 and 14kJmol−1, respectively, for A and B. This shows that the protonic conductivity is strongly influenced by the side chain dynamics and that the charge migration occurs through an ion hopping mechanism between different regions, consisting of micro-clusters of hydration water coordinated with the polar sulphonic groups of the side chains. The comparable activation energies and the values of the conductivity demonstrate that in these systems the conductivity is proportional to the concentration of the sulphonic groups. This shows also that these kinds of membranes, with a high concentration of SO3H are necessary in order to obtain materials with a high protonic conductivity with the capacity to retain water in bulk up to 145°C. [Copyright &y& Elsevier]

Abstract: The synthesis and structural characterization of two types of membranes with formulas {Si(CH3)3O[Si(CH3)HO]21.26-[Si(CH3)((CH2)3SO3H)O]1.8-[Si(CH3)((CH2)3Si(CH3)2O-)-O]14-Si(CH3)3} n (A) and {Si(CH3)3O[Si(CH3)HO]21.26-[Si(CH3)((CH2)3SO3H)O]1.8-[Si(CH3)((CH2)3(Si(CH3)2O-)-O[Si(CH3)((CH2)3Si(CH3)2O-)-OSi(CH3)3} n (B), (), were previously proposed. The ac electrical response of A and B was fully characterized in the 40Hz–2MHz frequency region by studying the impedance spectra in the medium and low frequency regions by equivalent circuits and complex dielectric spectra at high frequency in terms of dielectric relaxation modes. Results demonstrated that A and B conduct ionically by means of a proton exchange event which occurs via a vehicular mechanism between neighboring water clusters formed by water molecules aggregated around each sulfonic acid group of the siloxane side chains. The proton conductivities at 115°C of ca. 1.9×10−3 and 1.8×10−4 Scm−1 of fully hydrated membranes A and B, respectively, classify these silicone networks as good proton conductors. Membrane B was chosen for a closer investigation using NMR spectroscopy. Solid state 29Si MAS NMR experiments gave further insight about the three-dimensional structure. Proton diffusion measurements provided some encouraging results about proton dynamics of this membrane signaling the great potential of siloxanic based proton conductors. [Copyright &y& Elsevier]

Abstract: Two series of hybrid inorganic–organic polymer electrolytes of the organically modified ceramics as polymer electrolytes (ORMOCERS-APE) type with formulas {Al[O(CH2CH2O)8.7] ρ /(LiClO4) z } n (1.85≤ ρ ≤2.24, 0≤ z ≤1.06) and {Zr[O(CH2CH2O)8.7] ρ /(LiClO4) z } n (1.80≤ ρ ≤1.99, 0≤ z ≤0.90) were treated with CO2 in subcritical conditions (293K and 5MPa). The effect of CO2 on the samples was investigated by using ESEM, thermal analysis (TG and DSC) and broad band dielectric spectroscopy (BDS). Both complexes {Al[O(CH2CH2O)8.7] ρ /(LiClO4) z } n and {Zr[O(CH2CH2O)8.7] ρ /(LiClO4) z } n after CO2 treatment exhibited a change in the segmental relaxation with respect to the untreated samples. This phenomenon has been interpreted in terms of higher portion of free volume in the samples. The CO2 treatment primarily lowered the conductivity of {Al[O(CH2CH2O)8.7] ρ /(LiClO4) z } n complexes of about one order of magnitude, as opposed to {Zr[O(CH2CH2O)8.7] ρ /(LiClO4) z } n complexes, where an increment of two orders of magnitude was observed. In both cases the conductivity of the treated and untreated materials versus the reciprocal absolute temperature presents the typical Vogel–Tamman–Fulcher (VTF) behavior. The different effects on the conductivities of the treated complexes are explained in terms of the modified anion-trapping ability of Al centers and in terms of the interactions of subcritical CO2 with the host polymer and the salt. Insight about the conductivity mechanisms were provided by the study of the VTF parameters and the relaxation times determined from the Debye peaks of the imaginary resistivity, the imaginary permittivity and the correlated motion analysis. [Copyright &y& Elsevier]

Abstract: Photoreaction of the 6,9-dimethyl-4-methoxymethyl-2H-thieno[3,2-g]-1-benzopyran-2-one (compound I) and 4-acetoxymethyl-6,9-dimethyl-2H-thieno[3,2-g]-1-benzopyran-2-one (compound II) to DNA was studied. The quantitative evaluation of the photobound molecules was performed by means of inductively coupled plasma atomic emission spectrometry (ICP-AES), exploiting the presence of the sulphur atom inside the tricyclic chromophore. The concurrent estimation of the phosphorus atom, present exclusively in the macromolecule, allowed possible intercalation sites to be identified and their involvement in the photoaddition reaction to be determined. The development of a kinetic model made it possible to discriminate and evaluate the single kinetic events that constitute the overall photoaddition process of I and II to DNA. [Copyright &y& Elsevier]

Through photocopolymerisation of the cluster Zr4O2(OMc)12 bearing 12 polymerisable groups with methylmethacrylate in a monomer:cluster molar ratio of 50, a novel inorganic–organic hybrid thin film was obtained. The prepared thin film, having a thickness of about 70 μm, was characterised through dielectric spectroscopy. The dielectric spectra of the film were measured at different temperatures (20–73.4 °C) and in the frequency range 20 Hz–1 MHz. The α and β relaxations typical of polyalkylmethacrylate polymers were detected and the electric response mechanisms were investigated by analysing the dielectric spectra in terms of the Davidson–Cole phenomenological equation. Finally, a dielectric constant of 1.93 at 25 °C and 1 kHz was determined. This value classifies this system as a promising dielectric material for the development of electronic devices, such as polymer based field effect transistors. [Copyright &y& Elsevier]

This report describes the first attempt for the development of potentiometric H+ sensors based on liquid polymer electrolytes (PEs). The devices proposed here consist of a reference–polymer electrolyte–glass membrane electrode (R-PEGE) and an indicator electrode. Two types of indicator electrodes were obtained. The first uses a PVC-based polymer membrane as sensitive material, and was used to make an indicator–polymer electrolyte–polymer membrane electrode (I-PEPE). The second was assembled with a sensitive glass membrane, indicator–polymer electrolyte–glass membrane electrode (I-PEGE). Both the reference and indicator electrodes were prepared by the superposition of three layers of different materials, i.e., M&z.sfnc;PE&z.sfnc;SE&z.sfnc;, where M is Mg, Li or Ag, PE is PEG400/(LiCl)0.349 or PEG400/(δ-MgCl2)0.112 and SE is a sensitive glass- or PVC-based polymeric membrane. The response of the devices to the H+ concentration (a) is very linear from pH 2 to 13; (b) depends on temperature; (c) is very stable and reproducible; and (d) exhibits response times lower than 40 s. These properties make these devices very promising and indicate the polymer electrolytes as suitable materials for the development of innovative ion selective electrode (ISE) sensors. [Copyright &y& Elsevier]

The synthesis of Li2PdCl4 and Li3Fe(CN)6 precursors, and the preparation of the first lithium Z-IOPE material obtained by reacting these precursors with poly(ethylene glycol)600 (PEG600) is reported. This new material has been obtained through a sol⇒gel and gel⇒plastic transition. FIR and MIR spectroscopy studies, Raman laser and UV–vis investigations and detailed compositional data allowed us to propose a structural hypothesis and to detect the interactions between ions and the coordinating segments of the host network. It has been concluded that: (1) this compound is a mixed inorganic–organic network in which clusters formed by palladium and iron complexes are bonded together by PEG bridges; (2) the conformation of polyether chains in the bulk material is of the TGT (T=trans, G=gauche) type. The conductivity of the proposed [FexPdy(CN)zClv(C2nH4n+2On+1)Lil] is &ap;5.3×10−5 S cm−1 at 35.1 °C. [Copyright &y& Elsevier]

This paper describes the synthesis and characterization of three-dimensional hybrid inorganic–organic networks prepared by a polycondensation reaction between Zr(O(CH2)3CH3)4 and polyethylene glycol 400 (PEG400). Eleven hybrid networks doped with varying concentrations of LiClO4 salt were prepared. On the basis of analytical data and FT-Raman studies it was concluded that these polymer electrolytes consist of inorganic–organic networks with zirconium atoms bonded together by PEG400 bridges. These polymers are transparent with a solid rubber consistency and are very stable under inert atmosphere. Scanning electron microscopy revealed a smooth glassy surface. X-ray fluorescence microanalysis with energy dispersive spectroscopy demonstrated that all the constituent elements are homogeneously distributed in the materials. Thermogravimetric measurements revealed that these materials are thermally stable up to 262 °C. Differential Scanning Calorimetry measurements indicated that the glass transition temperature Tg of these inorganic–organic hybrids varies from −43 to −15 °C with increasing LiClO4 concentration. FT-Raman investigations revealed the TGT (T=trans, G=gauche) conformation of polyether chains and allowed characterization of the types of ion-ion and ion–polymer host interactions in the bulk materials. The conductivity of the materials at different temperatures was determined by impedance spectroscopy over the 20 Hz–1 MHz frequency range. Results indicated that the materials conduct ionically and that their ionic conductivity is strongly influenced by the segmental motion of the polymer network and the type of ionic species distributed in the bulk material. Finally, it is to be highlighted that the hybrid network with a nLi/nO molar ratio of 0.0223 shows a conductivity of ca. 1×10−5 S cm−1 at 40 °C. [Copyright &y& Elsevier]

In this paper are reviewed some of the most useful binding formalisms which have been developed in order to investigate the diversity of the commonly encountered receptor–ligand systems. Particularly, our attention is focused on the presentation and application of a general and rigorous thermodynamic treatment which explains in a simple and coherent way the non-linear profiles observed in the experimental binding, Scatchard, Hill and Adair plots. By applying this model, both qualitative and detailed quantitative investigations were carried out on the binding process of Al(III) to trypsin and dl-dipalmitoylphosphatidylcholine (DPPC) liposomes. Particularly, it has been demonstrated that: Al(III) interacts with liposomes in two binding sites with very different dissociation constants. The first one has been calculated to be 0.0168 μmol l−1 and the second 2.833 μmol l−1. The first is referred to the preferential interaction of Al3+ with the polar head of the phospholipid, while the second most likely regards the interaction of Al3+ with other peripheral sites. On the other hand, Al3+ interacts with trypsin in two types of binding sites. The first binding site with K1,1=0.2531 μmol l−1 and the second with K2,1=1.424 μmol l−1. [Copyright &y& Elsevier]

Two distinct types of host polymers, [EDTA]3[PEG400]7 and [EDTA][PEG400]2, consisting of polyethereal chains linked together by EDTA chelating units, were synthesized from ethylenediaminetetraacetic acid (EDTA) derivatives and PEG400. Their structures were revealed by analytical data, viscosimetric measurements and FTIR studies. Direct dissolution of δ-LiCl and δ-MgCl2 in these prepared host polymers resulted in the following electrolytic complexes: [EDTA]3[PEG400]7/(LiCl)6.39, [EDTA]3[PEG400]7/(MgCl2)8.23, [EDTA]3[PEG400]7/(LiCl)6.39(MgCl2)6.16, [EDTA][PEG400]2/(LiCl)2.26, [EDTA][PEG400]2/(MgCl2)1.98 and [EDTA][PEG400]2/(LiCl)2.26(MgCl2)1.98.Mid- and far-FTIR spectroscopic studies revealed the following properties for all the electrolytic complexes: (a) the polyethereal chains are in the TGT conformation; (b) the Mg2+ ion could be hexa- or heptacoordinated in chelating sites of EDTA; (c) the Li+ ion is preferentially coordinated by the oxygen atoms of the residual acetate groups and polyethereal moieties.Results of conductivity measurements performed at room temperature indicated that the proposed Mg polymer electrolytes (PE) might be very useful for the development of electrochemical transducers for measuring water hardness. [Copyright &y& Elsevier]

In this paper, eight solvent-free polymer electrolytes PEG400/(MgCl2)x (0.00329≤x≤0.7000) were prepared in order to investigate the mechanism of ionic motion and the interactions existing in these systems. The study was carried out by impedance spectroscopy in the 20-Hz to 1-MHz range at different temperatures. Real and imaginary components of conductivity spectra in terms of equivalent circuit analysis (EC) and correlated ionic motion analysis based on a generalized universal power law (UPL) were investigated. Results revealed that in the PEG400/(MgCl2)x, the ionic species formed in the bulk materials are crucial for the overall conductivity. Indeed, in PEG400/(MgCl2)x, conductivity is ionic and takes place through hopping of the cationic species Mg2+ and [MgCl]+ between the coordination sites present along the polyethereal chains. [Copyright &y& Elsevier]

Defect‐engineering is a viable strategy to improve the activity of nanocatalysts for the oxygen evolution reaction (OER), whose slow kinetics still strongly limits the broad market penetration of electrochemical water splitting as a sustainable technology for large‐scale hydrogen production. High‐entropy spinel oxides (HESOs) are in focus due to their great potential as low‐cost OER electrocatalysts. In this work, electrospun HESO nanofibers (NFs), based on (Cr,Mn,Fe,Co,Ni), (Cr,Mn,Fe,Co,Zn) and (Cr,Mn,Fe,Ni,Zn) combinations, with granular architecture and oxygen‐deficient surface are produced by calcination at low temperature (600 or 500 °C), characterized by a combination of benchtop analytical techniques and evaluated as electrocatalysts for OER in alkaline medium. The variation of HESO composition and calcination temperature produces complex and interdependent changes in the morphology of the fibers, crystallinity and inversion degree of the spinel oxide, concentration of the oxygen‐vacancies, cation distribution in the lattice, which mirror on different electrochemical properties of the fibers. The best electrocatalytic performance (overpotential and Tafel slope at 10 mA cm−2: 360 mV and 41 mV dec−1, respectively) pertains to (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 NFs calcined at 500 °C and results from the lower outer 3d‐electron number, eg filling closer to its optimal value and higher occupation of 16d sites by the most redox‐active species. [ABSTRACT FROM AUTHOR]

NiO-based films and nanostructured materials have received increasing attention for a variety of technological applications. Among the possible strategies for their fabrication, atomic layer deposition (ALD) and chemical vapor deposition (CVD), featuring manifold advantages of technological interest, represent appealing molecule-to-material routes for which a rational precursor design is a critical step. In this context, the present study is focused on the coordination sphere engineering of three heteroleptic Ni(II) β-diketonate–diamine adducts of general formula [NiL2TMEDA] [L = 1,1,1-trifluoro-2,4-pentanedionate (tfa), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionate (fod) or 2,2,6,6-tetramethyl-3,5-heptanedionate (thd), and TMEDA = N,N,N′,N′-tetramethylethylenediamine]. Controlled variations in the diketonate structure are pursued to investigate the influence of steric hindrance and fluorination degree on the chemico-physical characteristics of the compounds. A multi-technique investigation supported by density functional calculations highlights that all complexes are air-insensitive and monomeric and that their thermal properties and fragmentation patterns are directly dependent on functional groups in the diketonate ligands. Preliminary thermal CVD experiments demonstrate the precursors' suitability for the obtainment of NiO films endowed with flat and homogeneous surfaces, paving the way to future implementation for CVD end-uses. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the author discusses various articles within the issue on topics including article from researchers at Toyota Motor Co. on advances in the fuel cell stack, history of electrochemical production technology and reversible oxygen electrodes.

The in situ identification of fuel-cell material parameters is crucial both for guiding the research for advanced functionalized materials and for fitting multiphysics models, which can be used in fuel cell performance evaluation and optimization. However, this identification still remains challenging when dealing with direct measurements. This paper presents a method for achieving this aim by stochastic optimization. Such techniques have been applied to the analysis of fuel cells for ten years, but typically to specific problems and by means of semi-empirical models, with an increased number of articles published in the last years. We present an original formulation that makes use of an accurate zero-dimensional multi-physical model of a polymer electrolyte membrane fuel cell and of two cooperating stochastic algorithms, particle swarm optimization and differential evolution, to extract multiple material parameters (exchange current density, mass transfer coefficient, diffusivity, conductivity, activation barriers …) from the experimental data of polarization curves (i.e. in situ measurements) under some controlled temperature, gas back pressure and humidification. The method is suitable for application in other fields where fitting of multiphysics nonlinear models is involved. [ABSTRACT FROM AUTHOR]

• Green synthesis of MnO x NPs (20 nm) using olive leaf extract as a surfactant. • Mn 2 O 3 exhibits stability within the temperature range [600 °C-900 °C]. • Mn 3 O 4 appears between 300 °C and 600 °C, and reappears at 1000 °C. • MnO x structures show mesoporous characteristics with high surface area. This paper presents the green synthesis of manganese oxide nanoparticles using olive leaf extract (OLE). The extract functions as both a reducing agent, responsible for converting manganese ions into nanoparticles, and a capping agent, aiding in stabilizing the formed nanoparticles. Our focus lies on investigating the thermal stability, phase transformation, and decomposition temperatures of different manganese oxide phases in powder form as a function of the calcination temperature. Since phase transformation depends on temperatures change at the nanoscale both thermogravimetric and differential scanning calorimetry (TGA, DSC) are used to determine the new phase transformation temperatures of the synthesized nanoparticles. Moreover, the phase structure and the exact stoichiometry are studied using ex-situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning/transmission electron microscopy (SEM/TEM). XRD and XPS analyses reveal the formation of amorphous MnO x at room temperature (prior to calcination), transitioning to crystalline phases (Mn 2 O 3 and Mn 3 O 4) post-calcination. High-resolution TEM and SEM depict the formation of nanoparticles around 15 nm in size, exhibiting different shapes. BET technique calculations give a very high specific surface area, rending these nanoparticles excellent candidates for several applications. [ABSTRACT FROM AUTHOR]

The sodium-ion battery (Na-ion battery, NIB) is considered the most promising post-lithium energy storage technology, taking advantage of using the same manufacturing technology as Li-ion batteries (LIBs), while enabling the use of more abundant and economic, thus more sustainable, raw materials. Due to the inability of Na+ ions to be intercalated within the graphene-layered structure of graphite-based electrodes (the state of art anode material in LIBs), highly disordered and microporous carbons, known as hard carbons, are considered the anode material of choice for NIB technology. Biomass-derived biochar (BC) is one of the most relevant classes of hard carbons, exhibiting a good combination of sustainable fabrication, structural-morphological features and electrochemical performances. In this review, the main achievements on BC are rigorously reported from the production to the application into NIBs, with particular emphasis on the strategies to improve the electrochemical behaviour of BC by activating it and tailoring its chemical and structural properties. These strategies include selecting specific feedstocks, modulation of the pyrolysis temperature, pre- and post-production treatments, and materials engineering. The possible role of BC in sustainable NIBs development is also briefly discussed, together with some insights of its use in other post-Li energy storage systems and some concluding remarks and future direction of the research. • Na-ion battery is amongst the most promising post-Li energy storage technologies. • Na-ion battery requires the use of hard carbon as anode materials. • Biochar is one of the most relevant classes of hard carbons. • Biochar structure and chemical features can be tuned during or after production. • Main results on biochar in batteries are reported, from production to application. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: A solid film of Nafion has been prepared on the inner wall of a quartz tube. After pulsed photoexcitation, time-resolved electron spin resonance (TR-ESR) spectra have been recorded in the temperature range of 290–15 K. The spectra exhibit strongly electron-spin polarized signals in full absorption arising from the excited triplet state of Nafion. The absence of any resolved spectral features and the unusual narrowing of the TR-ESR signal linewidth with decreasing temperature are discussed in terms of the spin Hamiltonian of an excited triplet state with dynamic dipole–dipole interactions between the two unpaired electron spins. The existence of a triplet–triplet energy transfer process is considered, and a prominent role of hydrogen bonds of the surrounding water network is suggested. Finally, the time evolutions of the TR-ESR signals have been analysed, and the corresponding decay parameters have been obtained at low temperatures. Our results provide insight on the role of water as a medium for the conductivity mechanism in Nafion membranes. [Copyright &y& Elsevier]