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This work reports the fabrication of a starch-chitosan-based membrane for proton exchange membrane fuel cell applications at high temperatures, up to 145 °C. The membranes were fabricated by the solution casting method. Ionic liquids (ILs) were incorporated into the fabricated membranes to examine how they impact the proton conductivity. All the modified membranes generally demonstrated very good proton conductivity values in the range of 10−3 S/cm at room temperature. A noticeable increase in the proton conductivity was observed as the temperature was increased for the IL-based membranes. The IL-based membranes gave very high proton conductivities at 145 °C with a percentage increase of 209 % and 900 % compared to the reference membrane that contains starch and chitosan without any additives. The study reported structural interactions, particularly with the hydrophilic groups like the hydroxyl group, as revealed by FTIR analysis. These findings were supported by EIS measurements. The SEM images showed morphological alterations, and the XRD characterization indicated a shift toward an amorphous structure, implying more water retention in the polymer matrix, which explains the improved proton conductivity. The proton conductivity results as well as relevant water uptake properties reported in this work, appear to be promising for fuel cells operating above the boiling point of water. • Starch-chitosan-based membranes were developed for PEMFCs up to 145 °C. • Starch based membranes were modified with ionic liquids. • The starch modified membranes showed excellent proton conductivity up to 10−3 S/cm at room temperature. • The ionic liquids-starch membranes exhibited increased conductivity at higher temperatures. [ABSTRACT FROM AUTHOR]

The chemical compatibility of thin electrolyte layers and their support materials at high temperatures is crucial for the performance in solid oxide cells and membranes. This work describes the chemical interaction between the electrolyte material, BaCe 0.2 Zr 0.7 Y 0.1 O 3 + 0.5 wt% NiO (BCZY), and structural ceramics Al 2 O 3 , 8 mol% yttria stabilized zirconia (8YSZ), TiO 2 , CeO 2 and MgO during sintering. 1:1 wt% powder mixtures of the electrolyte material and structural ceramics were annealed at 1500 °C for 5 h, with the phase composition being determined through XRD analysis at room temperature. Subsequently, the material interaction between BCZY films deposited on the most promising structural ceramic MgO was investigated by SEM and EDS. In particular, the complex sintering requirements to form single-phase BCZY electrolyte layers is troubled upon coating and sintering BCZY on MgO. Hereby, the diffusion of NiO into the MgO support leads to a deficiency of NiO in the BCZY layer, making the solution and precipitation mechanism required to form the perovskitic phase unable to occur. In extreme scenarios, the electrolyte layer depletion of NiO can even cause the decomposition of a single-phase BCZY into BaZrO 3 , Ce-Y fluorite and a BCZY perovskite phase of undefined composition. [ABSTRACT FROM AUTHOR]

Nafion as a conducting polymer faces conduction challenges at high operating temperatures and low humidity levels, leading to an undesired fuel cell performance. Here, we offer a step forward towards the use of Nafion as a high-temperature/low-humidity membrane in fuel cells through the incorporation of phytic acid (IP6) by a doping process. The synergetic effect of IP6 on the physicochemical properties, mechanical characteristics, oxidative durability, proton conductivity, and fuel cell performance of Nafion membrane is studied. Compared to the pristine Nafion, the Nafion- IP6 membrane has shown a 3-fold increase in Young's modulus, a 83%-increase in water uptake, and around 6-fold increase in proton conductivity at 100 °C under 25% RH. The Ea has reached 8.3 kJ/mol, indicating a vehicular/Grotthuss proton conduction mechanism. The Nafion-IP6 based MEA has shown a 71%-increase in the output power density and a 54%-increase in the limiting current density compared to the pristine Nafion-based MEA. [Display omitted] • Developing a highly conductive Nafion-based membrane for high temperature fuel cells. • Incorporating phytic acid as a proton conductor into Nafion membrane. • Remarkable improvements of the physicochemical properties of Nafion membrane. • Application of Nafion/phytic acid membrane in high temperature/low humidity fuel cells. • A 71%-increase in power density of Nafion/phytic-MEA compared to pristine Nafion-MEA. [ABSTRACT FROM AUTHOR]

The perovskite-related oxides with intergrowth structure are a novel and promising class of protonic conductors. The development of this class of materials makes it possible to develop proton-conducting ceramics for intermediate temperatures (300–600 °C) for SOFCs (solid oxide fuel cells) applications. In this work, new complex oxide Ba5Y0.5In1.5Al2ZrO13 was obtained and investigated as a protonic conductor. Ba5Y0.5In1.5Al2ZrO13 shows the ability to water uptake and exhibits higher values of hydration degree (~ 0.40 mol H2O) than parent compound Ba5In2Al2ZrO13 (~ 0.30 mol H2O). IR spectroscopy confirmed the presence of OH−-groups in the hydrated phase Ba5Y0.5In1.5Al2ZrO13. The hydration ability is explained by the possibility of increasing the coordination number of barium in oxygen-deficient layers and the presence of sufficient space for the participation of OH−-groups in its coordination. Investigation of transport properties shows that in wet air (pH2O = 1.92·10−2 atm) below ~ 700 °C the conductivity is predominantly protonic. Proton mobility calculations show that the introduction of yttrium into the indium sublattice leads to an increase in mobility, which is probably due to an increase in the unit cell volume. [ABSTRACT FROM AUTHOR]

It is of great significance to develop high-temperature anhydrous proton conducting materials. Herein, we report a new strategy to significantly enhance the proton conductivity of covalent organic frameworks (COFs) through expanding the dimensionality of proton conduction. Three COF-based composites, COF-1@PA, COF-2@PA, and COF-3@PA (PA: phosphoric acid), are prepared by PA doping of three COFs with similar pore sizes but different amounts of hydrophilic groups. With the increase of hydrophilic groups, COFs can load more PA because of the enhanced hydrogen–bonding interactions between PA and the frameworks. powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and two-dimensional (2D) solid-state nuclear magnetic resonance (NMR) analyses show that PA can not only enter the channels of COF-3, but also insert into its 2D interlayers. This expands the proton conduction pathways from one-dimensional (1D) to three-dimensional (3D), which greatly improves the proton conductivity of COF-3. Meanwhile, the confinement effect of 1D channels and 2D layers of COF-3 also makes the hydrogen-bonded networks more orderly in COF-3@PA-30 (30 µL of PA loaded on COF-3). At 150 °C, COF-3@PA-30 exhibits an ultrahigh anhydrous proton conductivity of 1.4 S·cm−1, which is a record of anhydrous proton conductivity reported to date. This work develops a new strategy for increasing the proton conductivity of 2D COF materials. [ABSTRACT FROM AUTHOR]

As a low‐cost alternative to noble metals, Cu plays an important role in industrial catalysis, such as water‐gas shift reaction, methanol or ethanol oxidation, hydrogenation of oils, CO oxidation, among many others. An important step in optimizing Cu catalyst performance is control of nanoparticles size, distribution, and the interface with the support. While proton conducting perovskites can enhance the metal catalytic activity when acting as the support, there has been limited investigation of in situ growth of Cu metal nanoparticles from the proton conductors and its catalytic performance. Here, Cu nanoparticles are tracked exsolved from an A‐site‐deficient proton‐conducting barium cerate‐zirconate using scanning electron microscopy, revealing a continuous phase change during exsolution as a function of reduction temperature. Combined with the phase diagram and cell parameter change during reduction, a new exsolution mechanism is proposed for the first time which provides insight into tailoring metal particles interfaces at proton conducting oxide surfaces. Furthermore, the catalytic behavior in the CO oxidation reaction is explored and, it is observed that these new nanostructures can rival state of the art catalysts over long term operation. [ABSTRACT FROM AUTHOR]

The development of solid oxide fuel cells operating at medium temperatures (500–700 °C and even lower) requires the search for proton conductors based on complex oxides that would have a wide range of required properties. This task stimulates the search for new promising phases with proton conductivity. The new hexagonal perovskite-related compound Ba7In6Al2O19 was synthesized by the solid-state method. The phase was characterized by powder X-ray diffraction, thermogravimetric analysis, FT-IR spectroscopy, and impedance spectroscopy (in a wide range of temperatures, and partial pressures of oxygen at various atmospheric humidities). The investigated phase had a hexagonal structure with a space group of P63/mmc; the lattice parameters for Ba7In6Al2O19 are a = 5.921(2) Å, c = 37.717(4) Å. The phase is capable of reversible hydration and incorporates up to 0.15 mol H2O. IR-data confirmed that protons in the hydrated compound are presented in the form of OH–-groups. Electrical conductivity data showed that the sample exhibited dominant oxygen-ion conductivity below 500 °C in dry air and dominant proton conductivity below 600 °C in wet air. [ABSTRACT FROM AUTHOR]

The solid solution Ba 7 In 6– x Y x Al 2 O 19 (0≤ x ≤0.25) with a hexagonal perovskite-like structure was prepared by the solid-state route. The introduction of yttrium was accompanied by an increase in lattice parameters. The total conductivity as a function of p O 2 and T was measured at different humidity. The partial conductivities were found by transport number measurements and were fitted based on the defect formation model. Oxygen-ion and proton conductivities were found to increase with Y3+ content as a result of an increase in cell volume and free volume, which was accompanied by a decrease in the activation energy of both oxygen-ion and proton conductivity. Oxygen-ion conductivity and proton conductivity dominated below 500 °C in dry (p H 2 O =3.5×10−5 atm) and in wet (p H 2 O =1.92×10−2 atm) conditions, respectively. Doping makes it possible to increase proton conductivity by an order of magnitude (500 °C) and significantly increase the proton transport numbers. The prepared phases exhibited excellent chemical stability during thermal treatment in carbon dioxide (p CO 2 =1 atm). [Display omitted] • New hexagonal perovskites with intergrowth structure. • Ba 7 In 6– x Y x Al 2 O 19 were obtained. • Ba 7 In 6– x Y x Al 2 O 19 showed chemical resistance to carbon dioxide at 600 °C. • Y3+ doping led to an increase in ion conductivities and ion transport numbers. • Ba 7 In 6– x Y x Al 2 O 19 are predominantly proton conductors at temperatures below 500 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sm and Nd Co-doped BaCeO 3 was made using glycine-nitrate combustion technique. • The resultant oxide can conduct protons since the co-doping created oxygen vacancies. • The conductive form of proton conductor depends on hydrogen or water environment. • BaCe 0.8 Sm 0.2- x Nd x O 3-δ show superior electrical property at a certain ratio of Sm/Nd. BaCe 0.8 Sm 0.2- x Nd x O 3-δ (x = 0, 0.05, 0.1, 0.15) powder was prepared using the glycine-nitrate combustion method, its crystal structure, microscopic morphology and electrochemical properties were investigated. X-ray diffraction analysis showed that the BaCe 0.8 Sm 0.2- x Nd x O 3-δ powder with orthorhombic perovskite structure could be obtained after calcined at 1150 °C. Scanning electron microscopy showed that BaCe 0.8 Sm 0.2- x Nd x O 3-δ sintered samples exhibited a dense structure. Electrochemical impedance tests showed that the substitution of Nd3+ improved the electrical conductivity of the BaCeO 3 -based electrolyte materials. The proton conductivity of BaCe 0.8 Sm 0.15 Nd 0.05 O 3-δ samples reaches a maximum value of 0.035 S cm−1 in a wet air environment at 700 °C. [ABSTRACT FROM AUTHOR]

Abstract Protonic ceramic electrolysis cells (PCECs) are attractive electrochemical devices for converting electrical energy to chemicals due to their high conversion efficiency, favorable thermodynamics, fast kinetics, and inexpensive materials. Compared with conventional oxygen ion‐conducting solid oxide electrolysis cells, PCECs operate at a lower operating temperature and a favorable operation mode, thus expecting high durability. However, the degradation of PCECs is still significant, hampering their development. In this review, the typical degradations of PCECs are summarized, with emphasis on the chemical stability of the electrolytes and the air electrode materials. Moreover, the degradation mechanism and influencing factors are assessed deeply. Finally, the emerging strategies for inhibiting long‐term degradations, including chemical composition modifications and microstructure tuning, are explored.

Proton conductors are promising materials for clean energy, but most available materials exhibit sufficient conductivity only when chemically substituted to create oxygen vacancies, which often leads to difficulty in sample preparation and chemical instability. Recently, proton conductors based on hexagonal perovskite‐related oxides have been attracting attention as they exhibit high proton conductivity even without the chemical substitutions. However, their conduction mechanism has been elusive so far. Herein, taking three types of oxides with different stacking patterns of oxygen‐deficient layers (β‐Ba2ScAlO5, α‐Ba2Sc0.83Al1.17O5, and BaAl2O4) as examples, the roles of close‐packed double‐octahedral layers and oxygen‐deficient layers in proton conduction are shown. It is found that "undoped" β‐Ba2ScAlO5, which adopts a structure having alternating double‐octahedral layer and double‐tetrahedral layer with intrinsically oxygen‐deficient hexagonal BaO (h') layer, shows high proton conductivity (≈10−3 S cm−1 above 300 °C), comparable to representative proton conductors. In contrast, the structurally related oxides α‐Ba2Sc0.83Al1.17O5 and BaAl2O4 exhibit lower conductivity. Ab initio molecular dynamics simulations revealed that protons in β‐Ba2ScAlO5 migrate through the double‐octahedral layer, while the h′ layer plays the role of a "proton reservoir" that supplies proton carriers to the proton‐conducting double‐octahedral layers. The distinct roles of the two layers in proton conduction provide a strategy for developing high‐performance proton conductors. [ABSTRACT FROM AUTHOR]

BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb), one kind of promising electrolyte materials for proton-conducting solid oxide fuel cells (H+-SOFCs), generally suffers from the poor sinterability, leading to poor electrochemical performances lower than expected. Herein, a facile method, modified room temperature solid-state reaction (M-RTSSR) was proposed for synthesizing highly active BZCYYb nanopowders. Pure perovskite BZCYYb powders can be obtained at a low calcination temperature of 950 °C and a short dwelling time of 3 h. The highly active character allows the sintering temperature of BZCYYb electrolytes decrease from 1550 °C to 1450 °C, thus effectively suppressing the Ba evaporation and promoting the grain growth. The electrical conductivity measured at 700 °C in wet air is 2.6 × 10−2 S cm−1, which mainly benefits from the improvement of grain boundary conductivity. According to the analysis based on space charge layers, the enhanced electrical performance can be ascribed to their lower space charge potential (Δ φ (0)) and higher impurity blocking item (ω/d g). Finally, the anode-supported single cell with such BZCYYb electrolytes reaches a peak power density of 0.54 W cm−2 at 700 °C while taking humid H 2 (∼3 vol% H 2 O) as fuels and ambient air as oxidants. • A facile method is firstly proposed to synthesize highly active BZCYYb nanopowders. • The calcination temperature of pure BZCYYb nanopowders is decreased to 950 °C. • The sintering temperature of densified BZYCCb electrolytes is decreased by 100 °C. • The electrical conductivity of 2.6 × 10−2 S cm−1 at 700 °C in wet air is achieved. • The mechanism of enhanced electrical performances is clarified. [ABSTRACT FROM AUTHOR]

We synthesized a high‐nuclear isopolymolybdate cluster (n‐Bu4N)6H2[{Mo24O48(OMe)32}{Mo24O52(OMe)28}2] ⋅ 25H2O ⋅ 6CH3CN (1) by using [Mo6O19]2− as the base precursor. Crystallographic characterization shows the cluster is composed of an anionic [{Mo24O48(OMe)32}]8− cage and two charge‐neutral [{Mo24O52(OMe)28}] cages. Supported by the electrospray ionization mass spectrometry study, the polyoxoanion structural unit [Mo24O48(CH3O)27]3− demonstrates strong stability in acetonitrile solution. Moreover, 1 exhibits good proton conductivity of 1.79×10−3 S cm−1 at 358 K and 98 % relative humidity. [ABSTRACT FROM AUTHOR]

Abstract Among various types of alternative energy devices, solid oxide fuel cells (SOFCs) operating at low temperatures (300‐600°C) show the advantages for both stationary and mobile electricity production. Proton‐conducting oxides as electrolyte materials play a critical role in the low‐temperature SOFCs (LT‐SOFCs). This review summarizes progress in proton‐conducting solid oxide electrolytes for LT‐SOFCs from materials to devices, with emphases on (1) strategies that have been proposed to tune the structures and properties of proton‐conducting oxides and ceramics, (2) techniques that have been employed for improving the performance of the protonic ceramic‐based SOFCs (known as PCFCs), and (3) challenges and opportunities in the development of proton‐conducting electrolyte‐based PCFCs.

\nImpact statementDiscoveries and technological innovations over the past decade are transforming our understanding of the properties of ceramics, such as ‘hard’, ‘brittle’, and ‘homogeneous’. For example, inorganic crystals containing molecular anions exhibit excellent secondary battery characteristics, and the fusion of inorganic solids and molecules results in innovative catalytic functions and physical properties. Different from the conventional ceramics such as metal oxides that are formed by monatomic cations and anions, unique properties and functions can be expected in molecular-incorporated inorganic solids, due to the asymmetric and dynamic properties brought about by the constituent molecular units. We name the molecular-incorporated inorganic materials that produce innovative properties and functions as supra-ceramics. In this article, we describe various kinds of supra-ceramics from the viewpoint of synthesis, analysis and physical properties/functions for a wide range of applications.Recent discoveries/innovations are transforming ceramics by integrating molecular units, leading to new properties like enhanced battery performance and catalytic functions. Supra-ceramics, combining molecules and solids, promise innovative materials development. [ABSTRACT FROM AUTHOR]

As a promising electrolyte material for solid oxide fuel cells (SOFCs), BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) often surfers from its high sintering temperature, which causes Ba evaporation and sluggish grain growth, thus reducing the electrical conductivity. In this work, densified BZCYYb electrolytes were fabricated at temperatures as low as 1400 °C using the microwave sintering technique. Comparing with the conventional sintered ones, a temperature decrease of 150 °C is achieved. The Ba evaporation is effectively suppressed, and large grain sizes of ∼4 μm are obtained. The total conductivity for microwave sintered symmetric cell measured in wet air at 700 °C is 3.8 × 10−2 S cm−1, benefiting from both enhanced bulk conductivities by 1–2 times and grain boundary conductivities by 50 times. With the microwave sintered BZCYYb as electrolyte, an anode-supported cell reaches a maximum power density of 0.64 W cm−2 at 700 °C. • Densified BZCYYb electrolytes are fabricated by microwave sintering at 1400 °C. • The evaporation of Ba is effectively suppressed. • Large grain sizes of ∼4 μm are obtained. • Both bulk and grain boundary conductivities are dramatically enhanced. [ABSTRACT FROM AUTHOR]

The hexagonal perovskite Ba5In2Al2ZrO13 and In3+-doped phase Ba5In2.1Al2Zr0.9O12.95 were prepared by the solid-state synthesis method. The introduction of indium in the Zr-sublattice was accompanied by an increase in the unit cell parameters: a = 5.967 Å, c = 24.006 Å vs. a = 5.970 Å, c = 24.011 Å for doped phase (space group of P63/mmc). Both phases were capable of incorporating water from the gas phase. The ability of water incorporation was due to the presence of oxygen deficient blocks in the structure, and due to the introduction of oxygen vacancies during doping. According to thermogravimetric (TG) measurements the compositions of the hydrated samples corresponded to Ba5In2Al2ZrO12.7(OH)0.6 and Ba5In2.1Al2Zr0.9O12.54(OH)0.82. The presence of different types of OH−-groups in the structure, which participate in different hydrogen bonds, was confirmed by infrared (IR) investigations. The measurements of bulk conductivity by the impedance spectroscopy method showed that In3+-doping led to an increase in conductivity by 0.5 order of magnitude in wet air (pH2O = 1.92·10−2 atm); in this case, the activation energies decreased from 0.27 to 0.19 eV. The conductivity−pO2 measurements showed that both the phases were dominant proton conductors at T < 500 °C in wet conditions. The composition Ba5In2.1Al2Zr0.9O12.95 exhibited a proton conductivity ~10−4 S·cm−1 at 500 °C. The analysis of partial (O2−, H+, h•) conductivities of the investigated phases has been carried out. Both phases in dry air (pH2O = 3.5·10−5 atm) showed a mixed (oxygen-ion and hole) type of conductivity. The obtained results indicated that the investigated phases of Ba5In2Al2ZrO13 and Ba5In2.1Al2Zr0.9O12.95 might be promising proton-conducting oxides in the future applications in electrochemical devices, such as solid oxide fuel cells. Further modification of the composition and search for the optimal dopant concentrations can improve the H+-conductivity. [ABSTRACT FROM AUTHOR]

In 1678, Stefano Lorenzini first described a network of organs of unknown function in the torpedo ray-the ampullae of Lorenzini (AoL). An individual ampulla consists of a pore on the skin that is open to the environment, a canal containing a jelly and leading to an alveolus with a series of electrosensing cells. The role of the AoL remained a mystery for almost 300 years until research demonstrated that skates, sharks, and rays detect very weak electric fields produced by a potential prey. The AoL jelly likely contributes to this electrosensing function, yet the exact details of this contribution remain unclear. We measure the proton conductivity of the AoL jelly extracted from skates and sharks. The room-temperature proton conductivity of the AoL jelly is very high at 2 ± 1 mS/cm. This conductivity is only 40-fold lower than the current state-of-the-art proton-conducting polymer Nafion, and it is the highest reported for a biological material so far. We suggest that keratan sulfate, identified previously in the AoL jelly and confirmed here, may contribute to the high proton conductivity of the AoL jelly with its sulfate groups-acid groups and proton donors. We hope that the observed high proton conductivity of the AoL jelly may contribute to future studies of the AoL function.

Protonic ceramic electrolysis cells (PCECs) are attractive electrochemical devices for converting electrical energy to chemicals due to their high conversion efficiency, favorable thermodynamics, fast kinetics, and inexpensive materials. Compared with conventional oxygen ion‐conducting solid oxide electrolysis cells, PCECs operate at a lower operating temperature and a favorable operation mode, thus expecting high durability. However, the degradation of PCECs is still significant, hampering their development. In this review, the typical degradations of PCECs are summarized, with emphasis on the chemical stability of the electrolytes and the air electrode materials. Moreover, the degradation mechanism and influencing factors are assessed deeply. Finally, the emerging strategies for inhibiting long‐term degradations, including chemical composition modifications and microstructure tuning, are explored. [ABSTRACT FROM AUTHOR]

Dynamic self-assembly of liquid crystals favors the formation of hydrogen bond networks essential for anhydrous proton conduction. To endow liquid crystals with inherently exchangeable protons for proton conduction, protic 1-alkyl-3H-imidazolium hydrogen sulfates ([CnIm][HSO4]) with different lengths of alkyl chains are synthesized. Interdigitated smectic Ad (SAd) liquid crystal phases are observed for [CnIm][HSO4], in which the protic ionic pairs aggregate into lamellas. Electrochemical characterization reveals that the anhydrous proton conductivity of [CnIm][HSO4] reaches up to 5.3 mS cm–1 in the SAd phase. The single fuel cells fabricated from the [CnIm][HSO4]@PVDF supported membranes exhibit a peak power density of 2.6 mW cm−2 at 130 °C under non-humidified conditions. It was the enriched lamellar hydrogen bond networks formed by the protic ionic pairs that contribute to the anhydrous proton conduction. The protic ionic liquid crystals possess a great potential to construct electrochemical devices involving anhydrous proton conduction. Anhydrous proton conduction in protic ionic liquid crystals formed by 1-alkyl-3H-imidazolium hydrogen sulfates [ABSTRACT FROM AUTHOR]

Acceptor‐doped LaNbO4 is well documented to be a promising proton conductor. However, the relatively low proton conductivity limits its widely application, although many dopants are applied to overcome this shortcoming. Herein, a series of Li‐doped La1−xLixNbO4−x materials are prepared via a traditional solid‐state reaction method, with their phases, structures, and electrical properties being studied thoroughly. The results reveal an extremely low solubility for Li at the La site, which can be rationalized by the high endothermic solution energy of ≈7.57 eV calculated by the atomistic–static–lattice simulation method. Thus, all the prepared single‐phase samples (0 ≤ x ≤ 0.3) show similar chemical compositions, crystal structures, and electrical properties. [ABSTRACT FROM AUTHOR]

The development of solid oxide fuel cells operating at medium temperatures (500–700 °C and even lower) requires the search for proton conductors based on complex oxides that would have a wide range of required properties. This task stimulates the search for new promising phases with proton conductivity. The new hexagonal perovskite-related compound Ba7In6Al2O19 was synthesized by the solid-state method. The phase was characterized by powder X-ray diffraction, thermogravimetric analysis, FT-IR spectroscopy, and impedance spectroscopy (in a wide range of temperatures, and partial pressures of oxygen at various atmospheric humidities). The investigated phase had a hexagonal structure with a space group of P63/mmc; the lattice parameters for Ba7In6Al2O19 are a = 5.921(2) Å, c = 37.717(4) Å. The phase is capable of reversible hydration and incorporates up to 0.15 mol H2O. IR-data confirmed that protons in the hydrated compound are presented in the form of OH–-groups. Electrical conductivity data showed that the sample exhibited dominant oxygen-ion conductivity below 500 °C in dry air and dominant proton conductivity below 600 °C in wet air.

In this study for the first time, polybenzimidazole (PBI)/polyvinyl alcohol (PVA)/BaZrO3 hybrid nanocomposite membrane has been prepared for high-temperature Proton exchange membrane fuel cell. BaZrO3 nanoparticles as metal oxide were prepared by sol gel combustion method and a detailed structural study has been carried out by Rietveld refinement. The temperature and relative humidity dependence of the proton conductivity were investigated. The protonic conductivity of the hybrid nanocomposite has been studied by using a fuel cell testing station at 25–100 °C systematically. Hybrid nanocomposite membrane (PBI-PVA-BZO) demonstrates maximum proton ion conductivity 7.24 × 10−2 S/cm as compare to PVA, and hybrid composites (PVA-PBI). The highest peak power density of 47.5 mW/cm2 was achieved for polymer electrolyte membrane fuel cell which included hybrid nano-composite membranes at 70 °C. [ABSTRACT FROM AUTHOR]

Point defects such as oxygen vacancies and protonic interstitials are not only essential for ionic conductivity in oxides since they also affect the mechanical and electromechanical properties. These properties of nominally dry and hydrated proton‐conducting BaZr0.85M0.15O2.925+δH2δ (M = Al, Ga, Sc, In, Y, Eu) ceramics are investigated. Doping decreases Young's modulus with increasing ionic radii difference between the dopant and the host. Nominally dry samples show consistently higher Young's moduli than hydrated samples. All samples exhibit large non‐classical electrostriction, with a negative electrostriction coefficient M33<0. M33 shows saturation with the field and a non‐ideal Debye relaxation with frequency. The low‐frequency M33 value for both dry and hydrated samples shows a similar dependence on dopant radius as Young's modulus. For the hydrated samples, the relaxation frequency increases by a factor >100 in the series Ga‐Y, emphasizing the importance of proton trapping, with Y‐doped samples having minimal trapping energy. This coincides with the fact that the saturation strain for Y‐doped samples is also the smallest. In light of these findings, it is concluded that the present data give strong evidence for the existence of defect‐related elastic dipoles in acceptor doped barium zirconate and that the non‐classical electrostriction originates in their reorientation under electric field. [ABSTRACT FROM AUTHOR]

Acidic lyotropic liquid crystals (LLCs) have an advantage in constructing continuous proton conduction pathways owing to the well-defined structures, but the contribution of LLC to proton conductivity is hard to determine for the water-dependent nature of LLC. An aqueous 4-(1-ethyldecyl) benzenesulfonic acid solution, exhibiting a lamellar LLC phase at low hydration levels and becoming a micellar solution at high hydration levels, is employed to investigate structure-dependent proton conductivity. Electrochemical impedance spectrum (EIS) characterization reveals that the proton conductivity reaches a maximum of 173 mS cm−1 in the LLC phase. Owing to the self-assembling, the degree of dissociation of -SO3H tends to stabilize at 0.26 with increasing hydration levels. An integrated rate constant Ki is derived to evaluate the effect of self-assembly on proton conductivity, which reaches 1.90 × 107 mS cm5 mol−2 in the LLC but decreases to 1.23 × 107 mS cm5 mol−2 in the micellar solution. The single fuel cell fabricated from the LLC supported membrane exhibits a peak power density of 23.7 mW cm−2, confirming the enhanced proton conductivity under actual working conditions. The results quantitatively unveil the effect of aqueous self-assembly on proton conduction and offer a guide for achieving high conductivities in hydrated electrolytes with well-defined architectures. [ABSTRACT FROM AUTHOR]

Nanopowders of the compositions BaHf1 –xYbxO3 – δ (x = 0.04, 0.08, 0.10) and BaCe0.9 –xZrxY0.1O3 – δ (x = 0, 0.5, 0.6, 0.7, 0.8) were synthesized by the combined crystallization of nitric acid salts and the citrate-nitrate method. Those nanopowders were used to produce ceramic materials with a cubic crystal structure of the perovskite type, with a grain size of ~20–70 nm. The study of electrophysical properties revealed that they have a proton type of conductivity in the temperature range of 500–700°C; σ = 10–2–10–5 S/cm. The type and mechanism of electrical conductivity of ceramics of the composition BaHf1 –xYbxO3 – δ (x = 0.04, 0.08, 0.10) were studied both experimentally and using theoretical calculations by computer modeling using the electron density functional method; the results are in good agreement. The research shows the prospects of using the obtained ceramic materials as proton-conducting electrolytes for solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Supramolecular assemblies are vital for biological systems. This phenomenon in artificial materials is directly related to their numerous properties and their performance. Here, a simple approach to supramolecular assemblies is employed to fabricate highly efficient proton conducting molecular wires for fuel cell applications. Small molecule-based molecular assembly leading to a discotic columnar architecture is achieved, simultaneously with proton conduction that can take place efficiently in the absence of water, which otherwise is very difficult to obtain in interconnected ionic channels. High boiling point proton facilitators are incorporated into these columns possessing central ionic channels, thereby increasing the conduction multifold. Larger and asymmetrical proton facilitators disintegrated the self-assembly, resulting in low proton conduction efficiency. The highest conductivity was found to be approaching 10−2 S/cm for the molecular wires in an anhydrous state, which is ascribed to the continuous network of hydrogen bonds in which protons can hop between with a lower energy barrier. The molecular wires with ionic channels presented here have potential as an alternative to proton conductors operating under anhydrous conditions at both low and high temperatures.

Among various types of alternative energy devices, solid oxide fuel cells (SOFCs) operating at low temperatures (300‐600°C) show the advantages for both stationary and mobile electricity production. Proton‐conducting oxides as electrolyte materials play a critical role in the low‐temperature SOFCs (LT‐SOFCs). This review summarizes progress in proton‐conducting solid oxide electrolytes for LT‐SOFCs from materials to devices, with emphases on (1) strategies that have been proposed to tune the structures and properties of proton‐conducting oxides and ceramics, (2) techniques that have been employed for improving the performance of the protonic ceramic‐based SOFCs (known as PCFCs), and (3) challenges and opportunities in the development of proton‐conducting electrolyte‐based PCFCs. [ABSTRACT FROM AUTHOR]

Single-crystal neutron diffraction investigation on Cs4(HSO4)3(H2PO4) and Cs6H(HSO4)3(H2PO4)4 superprotonic crystals, belonging to CsHSO4–CsH2PO4–H2O salt system, is under taken to elucidate the precise hydrogen atom positions in these crystals. The investigation revealed that these crystals are very sensitive to the ambient conditions and can undergo deterioration due to fluctuation in air moisture content. Cs6H(HSO4)3(H2PO4)4 crystals are more stable as compared to Cs4(HSO4)3(H2PO4). Crystal structure of Cs6H(HSO4)3(H2PO4)4 is obtained both before and after deterioration, it is found that the asymmetric O–HO hydrogen bond between the PO4 and SO4 ions of this crystal becomes stronger after deterioration. This led to the shrinkage of the unit cell, and most likely prevented further deterioration. Diabatic state model for hydrogen bonds is used to obtain the energy contour for the O–H···O hydrogen bond of Cs6H(HSO4)3(H2PO4)4 crystal. The influence of this change in the hydrogen bonding on the proton conduction ability of the crystal is discussed. [ABSTRACT FROM AUTHOR]

Rare-earth doped CeO 2 materials find extensive application in high-temperature energy conversion devices such as solid oxide fuel cells and electrolyzers. However, understanding the complex relationship between structural and electrical properties, particularly concerning rare-earth ionic size and content, remains a subject of ongoing debate, with conflicting published results. In this study, we have conducted comprehensive long-range and local order structural characterization of Ce 1- x Ln x O 2- x /2 samples ( x ≤ 0.6; Ln = La, Nd, Sm, Gd, and Yb) using X-ray and neutron powder diffraction, Raman spectroscopy, and electron diffraction. The increase in the rare-earth dopant content leads to a progressive phase transformation from a disordered fluorite structure to a C-type ordered superstructure, accompanied by reduced ionic conductivity. Samples with low dopant content ( x = 0.2) exhibit higher ionic conductivity in Gd 3+ and Sm 3+ series due to lower lattice cell distortion. Conversely, highly doped samples ( x = 0.6) exhibit superior conductivity for larger rare-earth dopant cations. Thermogravimetric analysis confirms increased water uptake and proton conductivity with increasing dopant concentration, while the electronic conductivity remains relatively unaffected, resulting in reduced ionic transport numbers. These findings offer insights into the relationship between transport properties and defect-induced local distortions in rare-earth doped CeO 2 , suggesting the potential for developing new functional materials with mixed ionic oxide, proton, and electronic conductivity for high-temperature energy systems.

Proton conducting Y‐doped BaZrO3, BaCeO3 and their solid solutions are receiving increasing attention due to their promising application as electrolytes in ceramic fuel cells and electrolysis cells. However, the literature indicates a clear tendency that the performance of the cells increases with increasing Ce content in the electrolyte. In this work, to elucidate this phenomenon, a systematic work is performed on investigating the phase, hydration, and transport behaviors of BaZr0.8−xCexY0.2O3−δ (BZCY20). The results reveal that in the temperature range between 500 and 700 °C, with increasing Ce content, the dehydration temperature elevates and the proton concentration increases, showing that the Ce component favors the stabilization of protons. Furthermore, the transport number of hole conduction decreases, whereas the transport number of ionic conduction increases with the increasing Ce content. By further separating the contribution of oxide ions and protons, it is found that the oxide ion conductivity increases with the increasing Ce content at higher temperatures of 600 and 700 °C. Such decreased hole conductivity and increased oxide ion conductivity result in the enhancement of the ionic conduction of BZCY20 with increasing Ce content, and therefore improve the performance of fuel cells and electrolysis cells. [ABSTRACT FROM AUTHOR]

Proton conducting polymer blend electrolytes based on cornstarch and polyvinyl pyrrolidone (PVP) with ammonium bromide (NH4Br) were prepared by the technique of solution casting. Enhancement of amorphous nature by the addition of NH4Br has confirmed by XRD. In FTIR,by the addition of NH4Br salt in the optimized blend system, there occurs a change like altering the peak intensity, peak shape, and position. This reveals the appearance of complex formation between the polymer and salt. At 358 K, 30 wt.% of NH4Br added system shows the maximum conductivity (1.31 × 10−4 S cm−1). The conduction mechanism of higher conducting polymer blend electrolytes follows the quantum mechanical tunneling (QMT) at mid-frequency and overlapping large polaron tunneling (OLPT) at higher frequency. High dielectric constant and low relaxation time of ions in polymer chain are obtained for 30 wt.% of NH4Br added polymer blend electrolyte. From Wagner's polarization technique, it is established that conduction present in the polymer electrolytes is predominately due to ions. Faradaic pseudo capacity behaviour has observed in higher conducting sample by cyclic voltammetry. The electrochemical cell has prepared by the higher conducting polymer electrolyte and the open circuit potential (OCP) of 1.24 V has achieved from prepared electrochemical cell. [ABSTRACT FROM AUTHOR]

Proton conductor inorganic acid Cs2(HSO4)(H2PO4) is investigated by molecular dynamics (MD) simulation in its molten and glass states using the screened Born–Mayer (BM) type potentials. The glass formation is analysed by the change of structure, i.e. pair distribution functions, diffusion coefficient of constituent ions and Voronoi polyhedron. The electrical properties are also obtained by ab initio calculation, which shows a significant difference in the density of states concerning H and S/P atoms. These facts show a similar H diffusion mechanism as the solid state occurs in the glass state. [ABSTRACT FROM AUTHOR]

Reversible solid oxide cells based on ceramic proton conductors have potential to be the most efficient system for large‐scale energy storage. The performance and long‐term durability of these systems, however, are often limited by the ionic conductivity or stability of the proton‐conducting electrolyte. Here new family of solid oxide electrolytes, BaHfxCe0.8−xY0.1Yb0.1O3−δ (BHCYYb), which demonstrate a superior ionic conductivity to stability trade‐off than the state‐of‐the‐art proton conductors, BaZrxCe0.8−xY0.1Yb0.1O3−δ (BZCYYb), at similar Zr/Hf concentrations, as confirmed by thermogravimetric analysis, Raman, and X‐ray diffraction analysis of samples over 500 h of testing are reported. The increase in performance is revealed through thermodynamic arguments and first‐principle calculations. In addition, lab scale full cells are fabricated, demonstrating high peak power densities of 1.1, 1.4, and 1.6 W cm−2 at 600, 650, and 700 °C, respectively. Round‐trip efficiencies for steam electrolysis at 1 A cm−2 are 78%, 72%, and 62% at 700, 650, and 600 °C, respectively. Finally, CO2H2O electrolysis is carried out for over 700 h with no degradation. [ABSTRACT FROM AUTHOR]

Reversible solid oxide cells based on ceramic proton conductors have potential to be the most efficient system for large‐scale energy storage. The performance and long‐term durability of these systems, however, are often limited by the ionic conductivity or stability of the proton‐conducting electrolyte. Here new family of solid oxide electrolytes, BaHfxCe0.8−xY0.1Yb0.1O3−δ (BHCYYb), which demonstrate a superior ionic conductivity to stability trade‐off than the state‐of‐the‐art proton conductors, BaZrxCe0.8−xY0.1Yb0.1O3−δ (BZCYYb), at similar Zr/Hf concentrations, as confirmed by thermogravimetric analysis, Raman, and X‐ray diffraction analysis of samples over 500 h of testing are reported. The increase in performance is revealed through thermodynamic arguments and first‐principle calculations. In addition, lab scale full cells are fabricated, demonstrating high peak power densities of 1.1, 1.4, and 1.6 W cm−2 at 600, 650, and 700 °C, respectively. Round‐trip efficiencies for steam electrolysis at 1 A cm−2 are 78%, 72%, and 62% at 700, 650, and 600 °C, respectively. Finally, CO2H2O electrolysis is carried out for over 700 h with no degradation. [ABSTRACT FROM AUTHOR]

The aim of this work was to determine the influence of glassy Ba–Ce–Y–Si–P–O phase, prepared by sol-gel method and introduced into the BaCe 0.9 Y 0.1 O 3 host material on the selected properties of obtained materials. Three composite materials with different content of modifying phase (3, 6 and 18 wt%) were prepared. It was found that the introduction of an additional amorphous phase leads to the decrease of the electrical conductivity in the measured temperature range, both in grain interior and grain boundary regions. The observed change of conduction mechanism can be explained by the modification of the chemical composition of BaCe 0.9 Y 0.1 O 3 due to reaction with modifying phase at the stage of material preparation. Based on obtained results further optimisation of modifier phase composition and the preparation conditions leading to the materials with improved properties can be proposed. [ABSTRACT FROM AUTHOR]

In this paper, series of Na-doped La 1- x Na x PO 4- x (0 ≤ x ≤ 0.2) materials are synthesized by solid state reaction method, and single phase has been obtained for 0 ≤ x ≤ 0.1. The doped materials show significantly improved conductivity under dry environment by about four orders of magnitude, but dominated by sodium ion conduction, with ~ 10% oxide ion conduction. The oxide ion conducting mechanism in LaPO 4 -based materials is studied for the first time by molecular dynamic simulations based on interatomic potential approach. This work therefore provides a comprehensive view of the underlying oxide ion migration mechanism for LaPO 4 -based materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]

This review summaries state-of-the-art developments of POM-based molecular and composite materials involving dye sensitized solar cells, perovskite solar cells, organic solar cells, lithium-ion batteries, zinc-ion batteries, solid-state proton conductors, and electrochemical biosensors, and provides a future perspective. [Display omitted] • Updated developments of POM-based molecular and composite materials. • Application advances for energy storage and conversion. • Application advances for solid-state proton conductors. • Application advances for electrochemical biosensors. Polyoxometalates (POMs) feature diversified structures, tailorable compositions, adjustable redox behaviors, and multielectron storage capability. As such, POM-based materials provide vast opportunities for a plethora of wide applications, which has triggered the enthusiasm of academic and industrial researchers. Moreover, developing advanced POM-based materials with tailored properties allows further performance enhancement and the emergence of novel functionalities. Furthermore, the substantial progress of POMs over the past five years necessitates an updated summary as well as adaptable perspectives to fuel the future advancement with respect to both fundamental science and practical applications. Herein, on the basis of their intrinsic electronic, optoelectronic, and electrochemical properties, applications of POM-based materials in solar cells, ion batteries, solid-state proton conductors and electrochemical biosensors are summarized with a primary focus on up-to-date developments. In light of the interdisciplinary nature of these applications, fundamental knowledge of each relevant area is provided at the beginning as the basis for the subsequent representative advancements, wherein mechanistic elucidations shedding light on structure–property–performance relationships are highlighted. Finally, personal perspectives are proposed to hopefully offer valuable insights into the accelerated development of POM-based materials in the future. [ABSTRACT FROM AUTHOR]

This work deals with the development of graphene oxide (GO)-based self-assembling membranes as possible innovative proton conductors to be used in polymer electrolyte membrane fuel cells (PEMFCs). Nowadays, the most adopted electrolyte is Chemours’ Nafion; however, it reveals significant deficiencies such as strong dehydration at high temperature and low humidity, which drastically reduces its proton conductivity. The presence of oxygenated moieties in the GO framework makes it suitable for functionalization, which is required to enhance the promising, but insufficient, proton-carrying features of GO. In this study, sulfonic acid groups (–SO3H) that should favor proton transport were introduced in the membrane structure via a reaction between GO and concentrated sulfuric acid. Six acid-to-GO molar ratios were adopted in the synthesis procedure, giving rise to final products with different sulfonation degrees. All the prepared samples were characterized by means of TGA, ATR-FTIR and Raman spectroscopy, temperature-dependent XRD, SEM and EDX, which pointed out morphological and microstructural changes resulting from the functionalization stage, confirming its effectiveness. Regarding functional features, electrochemical impedance spectroscopy (EIS) as well as measurements of ion exchange capacity (IEC) were carried out to describe the behavior of the various samples, with pristine GO and commercial Nafion® 212 used as reference. EIS tests were performed at five different temperatures (20, 40, 60, 80 and 100 °C) under high (95%) and medium (42%) relative humidity conditions. Compared to both GO and Nafion® 212, the sulfonated specimens demonstrate an increase in the number of ion-carrying groups, as proved by both IEC and EIS tests, which reveal the enhanced proton conductivity of these novel membranes. Specifically, an acid-to-GO molar ratio of 10 produces a six-fold improvement of IEC (4.23 meq g−1) with respect to pure GO (0.76 meq g−1), while a maximum eight-fold improvement (5.72 meq g−1) is achieved in SGO-15.

18O and 2H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo2O5+δ (PBCO) in flowing air containing 200 mbar of 2H216O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity (~1.3 × 10−11 cm2s−1) at this temperature and that the presence of water (2H216O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of ~3. The 2H distribution, as inferred from the 2H216O− SIMS signal, shows an apparent depth profile which could be interpreted as 2H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials.

The properties of proton conductors determine the operating temperature range of fuel cells. Typically, phosphoric acid (PA) proton conductors exhibit excellent proton conductivity owing to their high proton dissociation and self-diffusion abilities. However, at low temperatures or high current densities, water-induced PA loss causes rapid degradation of cell performance. Maintaining efficient and stable proton conductivity within a flexible temperature range can significantly reduce the start-up temperature of PA-doped proton exchange membrane fuel cells. In this study, a dual-proton conductor composed of an organic phosphonic acid (ethylenediamine tetramethylene phosphonic acid, EDTMPA) and an inorganic PA is developed for proton exchange membranes. The proposed dual-proton conductor can operate within a flexible temperature range of 80-160 °C, benefiting from the strong interaction between EDTMPA and PA, and the enhanced proton dissociation. Fuel cells with the EDTMPA-PA dual-proton conductor showed excellent cell stability at 80 °C. In particular, under the high current density of 1.5 A cm -2 at 160 °C, the voltage decay rate of the fuel cell with the dual-proton conductor is one-thousandth of that of the fuel cell with PA-only proton conductor, indicating excellent stability., (© 2024 Wiley‐VCH GmbH.)

The increase in conductivity with temperature in 1H-pyrazol-2-ium 2,6-dicarboxybenzoate monohydrate was analyzed, and the influence of the mobility of the water was discussed in this study. The electric properties of the salt were studied using the impedance spectroscopy method. WB97XD/6-311++G(d,p) calculations were performed, and the quantum theory of atoms in molecules (QTAiM) approach and the Hirshfeld surface method were applied to analyze the hydrogen bond interaction. It was found that temperature influences the spectroscopic properties of pyrazolium salt, particularly the carbonyl and hydroxyl frequencies. The influence of water molecules, connected by three-center hydrogen bonds with co-planar tetrameters, on the formation of structural defects is also discussed in this report.

Dicarboxylic acid salts are a good group of compounds in which one can study a variety of supramolecular structures as dimers, catemer chains, and rings and are interesting for crystal engineering of proton conductors for applications in solid‐state hydrogen fuel cells. The optical properties of the new proton‐conducting compound of pyrazole with oxalate acid were investigated using Raman and IR spectroscopy taking into account the formal classification of the fundamental modes. To gain more information on the intermolecular interactions and molecular vibrations, experimental data obtained for 1H‐pyrazol‐2‐ium hydrogen oxalate salt were supported by the quantum‐chemical calculations (density functional theory), Hirshfield surfaces and fingerprint plots analysis, and Bader theory calculations. Topological properties of the planar oxalic acid dimer and oxalic acid pyrazole tetramer have been calculated within the quantum theory of atoms in molecules, and it was shown that dominant types of interactions in the investigated salt are medium strength hydrogen‐bonding interactions. [ABSTRACT FROM AUTHOR]

In this work, lanthanum orthoniobates doped with either antimony, calcium, or both have been synthesized and studied. The water uptake of the investigated materials has been analyzed by means of thermogravimetric studies. The results show the difference between the thermodynamics of hydration between the lanthanum orthoniobate system and other proton conducting ceramics. The relation between the water uptake and effective acceptor doping for the investigated system has been found, and the energetics of the water uptake relation are discussed. [ABSTRACT FROM AUTHOR]

Using a citrate-nitrate process, BaCe 0.9-x Zr x Y 0.1 O 3-δ (x = 0, 0.5, 0.6, 0.7 and 0.8) nanopowders were synthesized, on the basis of which proton-conducting solid electrolytes (average size of coherent scattering region (CSR) - 15–53 nm) were obtained by spark plasma sintering (SPS) at a low temperature (900°С). The dependence of phase composition, microstructure and electrophysical properties of the obtained samples on ZrO 2 content and consolidation conditions was established. It was found that the BaCe 0.4 Zr 0,5 Y 0.1 O 3-δ solid solution had the highest electrical conductivity among zirconium-containing ceramic materials in the studied concentration range. It was shown that SPS is a promising method for obtaining solid electrolytes for proton-conducting solid oxide fuel cells (PCFC) at lower temperatures (by 400–500°С), compared to traditionally-used temperature conditions (1400–1800 °C). • BaCe 0.9-x Zr x Y 0.1 O 3-δ (BCZY) nanopowders were synthesized by a citrate-nitrate method. • Spark plasma sintering (900 °C) was used to consolidate the obtained powders. • Electrical conductivity measurements were carried out at different humidity levels. • Energy efficient technology for BCZY electrolytes fabrication has been developed. [ABSTRACT FROM AUTHOR]