Search

Proton-transfer mechanisms and hydration states were investigated in chitin films possessing the functionality of fuel-cell electrolytes. The absolute hydration number per chitin molecule (N) as a function of relative humidity (RH) was determined from the OH stretching bands of H2O molecules, and the proton conductivity was found to enhance above N = 2 (80%RH). The FIR spectrum at 500–900 cm−1 for 20%RH (N < 1) together with first-principles calculations clearly shows that the w1 site has the same hydration strength as the w2 site. The molecular dynamics simulations for N = 2 demonstrate that H2O molecules with tiny fluctuations are localized on w1 and w2, and the hydrogen-bond (HB) network is formed via the CH2OH group of chitin molecules. Shrinkage of the O–O distance (dOO), which synchronizes with the barrier height, is required for proton transfer from H3O+ to adjacent CH2OH groups or H2O molecules. Nevertheless, dOO is hardly modulated for N = 2 because H2O molecules are strongly constrained on w1 and w2, and therefore, the transfer probability becomes small. For N = 3, novel HBs emerged between the additional H2O molecules broadly distributed on the w3 site and H2O molecules on w1 and w2. The transfer probability is enhanced because large fluctuations and diffusions in the whole H2O molecule yield large modulations of dOO. Consequently, long-range proton hopping is driven by the Zundel-type protonated hydrates in the water network. [ABSTRACT FROM AUTHOR]

The cathodic catalytic activity for the oxygen reduction reaction (ORR) plays a critical role in determining the performance of proton-conducting solid oxide fuel cells (P-SOFCs). BaCo 0.4 Fe 0.4 Zr 0.2 O 3-δ (BCFZ) has emerged as a promising cathode for P-SOFCs due to its triple-phase conductivity. Nevertheless, its suboptimal proton conductivity and hydration ability at intermediate temperatures prevent it from achieving the anticipated ORR catalytic activity. To address these limitations, this study explores the enhancement of electrocatalytic activity in BCFZ through alkali metal doping and A-site defect construction. The effects of such modifications on oxygen surface exchange kinetics and ORR catalytic activity are systematically investigated. The findings reveal that BCFZ exhibits relatively low parameters in terms of electronic conductivity, oxygen ion conductivity, oxygen vacancy concentration, k chem , and D chem. Conversely, these parameters are markedly improved in A-site deficient BCFZ (D-BCFZ) and Na/K-doped BCFZ. Consequently, the enhancement of these properties yields a significant increase in ORR catalytic activity, with D-BCFZ demonstrating the best electrochemical performance. Specifically, P-SOFC with D-BCFZ cathode achieves an R p value of just 0.073 Ω cm2 and a P max value of 0.928 W cm−2 at 650 °C. This study provides theoretical insight into the mechanisms by how alkali metal doping and defect construction enhance the ORR catalytic activity of BCFZ. These findings offer valuable guidance for the development and optimization of high-performance P-SOFC cathodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A zwitterion-modified fiber substrate was used to fill with SPEEK to prepare PEM. • Zwitterionic interface provided fast channels for proton transport. • High proton conductivity and chemical stability were obtained. • Better DMFC performance than that of commercial Nafion 212 membrane was obtained. Proton exchange membranes with high ionic conductivity and good chemical stability are critical for achieving high power density and long lifespan of direct methanol cells (DMFCs). Herein, a zwitterionic molecule was grafted onto the surface of polyvinylidene fluoride (PVDF) nanofibers to obtain functionalized PVDF porous substrate (SBMA-PDA@PVDF). Then, sulfonated poly(ether ether ketone) (SPEEK) was filled into the pores of SBMA-PDA@PVDF, and further ionic cross-linked via H 2 SO 4 to prepare the composite membrane (SBMA-PDA@PVDF/SPEEK). The basic groups on the zwitterionic interface could not only establish ionic cross-linking with SPEEK to increase chemical stability and reduce swelling, but also serve as the adsorption sites for subsequent H 2 SO 4 cross-linking to significantly enhance proton conductivity. Super-high proton conductivity (165.34 mS cm−1, 80 °C) was achieved for the membrane, which was 2.12 times higher than that of the pure SPEEK. Moreover, the SBMA-PDA@PVDF/SPEEK membrane exhibited remarkably improved oxidative stability of 91.6 % mass retention after soaking in Fenton's agent for 12 h, while pure SPEEK completely decomposed. Satisfactorily, the DMFC assembled with SBMA-PDA@PVDF/SPEEK exhibited a peak power density of 99.01 mW cm−2, which was twice as much as that of commercial Nafion 212 (48.88 mW cm−2). After 235 h durability test, only 11 % voltage loss was observed. [ABSTRACT FROM AUTHOR]

This study loaded different amounts of UiO‐66‐NH2 onto sulfonated polyphenylene sulfide fibers (SPPS), successfully loading UiO‐66‐NH2 on SPPS fibers confirmed by energy dispersive x‐ray spectroscopy, x‐ray diffraction, and Fourier transform infrared spectroscopy. The UiO‐66‐NH2‐X@SFM were then impregnated in Nafion solution to obtain UiO‐66‐NH2‐X@SFM/Nafion composite membranes. The thermal stability, dimensional stability, mechanical properties, proton conductivity, methanol resistance, and other properties of the UiO‐66‐NH2‐X@SFM/Nafion composite membranes were subsequently comprehensively characterized. The proton conductivity of the UiO‐66‐NH2‐8@SFM/Nafion composite membrane at 80°C and 100% RH was measured to be 0.286 S cm−1, which exhibited a significant enhancement of 1.75 times compared with the original membrane. Simultaneously, the composite membrane demonstrated a remarkable reduction in methanol permeation rate. At 40°C and 100% RH, the UiO‐66‐NH2‐8@SFM/Nafion composite membrane has a selectivity of up to 20.7 × 104 S s cm−3 and a single cell density of 88.3 m W cm−2 at 60°C and 100% RH. [ABSTRACT FROM AUTHOR]

In this survey, the different weight ratios of polybenzimidazole (PBI)/polyvinyl alcohol (PVA) blend polymer membranes were produced using the solution‐casting method. The crosslinking agents of phosphoric acid (PA) and glutaraldehyde (GA) were studied separately to prevent the PVA water solubility in the PBI/PVA blend membrane structure. The GA crosslinking (24 h) successfully prevented membrane solubility, reducing it to below 1%. The chemically crosslinked blend membrane (Cr‐PBI/PVA‐9:1) has the highest proton conductivity result which is 0.209 S cm−1 at 80°C and it has excellent oxidative stability since the membrane only lost 4% of its weight in a Fenton agent after 96 h. The Cr‐PBI/PVA‐9:1 also has higher proton conductivity than the commercial PBI membrane (0.122 S cm−1 at 80°C). The glass transition temperature of the synthesized Cr‐PBI/PVA‐9:1 blend membrane is greater than the synthesized PBI membrane (390°C). The current density and power density measured at 0.6 V for the synthesized Cr‐PBI/PVA‐9:1 membrane were found to be 504 mA cm−2and 251 mW cm−2. This work sheds light on the potential use of PVA in PEMFC applications by mixing PVA with a high‐temperature polymer like PBI and crosslinking the membrane with a prepared GA crosslinking agent. [ABSTRACT FROM AUTHOR]

A novel dimeric structure based on trilacunary Keggin-type [SbW9O33]9− was synthesized and comprehensively characterized. Different from the conventional dimeric structures, the compound (NH4)10[(SbW9O33)2(UO2)2(H2O)2(SbOH)2]·7H2O ({U2Sb4}) features two additional Sb3+ cations. The successful synthesis of {U2Sb4} reveals the significant role of heteroatoms in structural modulation. The dimer forms a hydrogen-bonded network with water molecules and NH4+ and is therefore expected to exhibit remarkable proton conductivity. Proton conduction studies revealed that {U2Sb4} was a temperature and humidity-dependent proton conductor with conductivity reaching up to 2.50 × 10−2 S cm−1 at 85 °C and 85% RH. [ABSTRACT FROM AUTHOR]

Surface proton hopping conduction (SPHC) mechanisms is an important proton conduction mechanism in conventional polymer electrolytes, along with the Grotthuss and vehicle mechanisms. Due to the small diffusion coefficient of protons in the SPHC mechanism, few studies have focused on the SPHC mechanism. Recently, it has been found that a dense alignment of SO3− groups significantly lowers the activation energy in the SPHC mechanism, enabling fast proton conduction. In this study, a series of polymerizable amphiphilic‐zwitterions is prepared, forming bicontinuous cubic liquid‐crystalline assemblies with gyroid symmetry in the presence of suitable amounts of bis(trifluoromethanesulfonyl) imide (HTf2N) and water. In situ polymerization of these compounds yields gyroid‐nanostructured polymer films, as confirmed by synchrotron small‐angle X‐ray scattering experiments. The high proton conductivity of the films on the order of 10−2 S cm−1 at 40 °C and relative humidity of 90% is based solely on the SPHC mechanism. [ABSTRACT FROM AUTHOR]

This study investigates the development of a biopolymer blend electrolyte composed of alginate and poly (vinyl alcohol) (PVA), doped with glycolic acid (GA) to enhance H+ conductivity. The addition of GA significantly impacts the biopolymer blend's physicochemical properties and ionic conduction performance. Fourier transform infrared (FTIR) spectroscopy verified the intricate interactions and hydrogen bonding between the alginate-PVA matrix and GA. The addition of GA was shown to increase the amorphous phase, as observed through X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. This increase in the amorphous phase was found to enhance the thermal stability. Impedance analysis demonstrated a significant increase in ionic conductivity from approximately ∼10⁻⁸ S cm⁻1 for the undoped blend to 3.45 × 10⁻⁵ S cm⁻1 with 30 wt% GA (sample GA-30). The enhanced H+ conduction behaviour was consistent across various temperatures, adhering to the Arrhenius rule. These findings suggest that the alginate-PVA-GA system is a promising candidate for efficient proton transport applications. • A bio-based polymer blend electrolyte composed of alginate-PVA containing H + carriers has been successfully prepared. • Amorphous Structure : GA doping transforms alginate-PVA into a highly amorphous, ion-conductive structure. • Strong Hydrogen Bonding : FTIR shows enhanced hydrogen bonding, aiding proton conduction via Grotthuss mechanism. • Thermal Stability : TGA confirms GA-doped alginate-PVA maintains thermal stability and boosts proton conductivity. • Enhanced Proton Conductivity : Glycolic acid-doped alginate-PVA boosts conductivity to 3.45 × 10⁻⁵ S cm⁻1. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) is an advantageous polymer due to its renewable nature, low cost, environmental compatibility, biocompatibility, biodegradability, chemical stability, and ease of modification. With these advantages, BC is an interesting candidate for the development of novel eco-friendly materials for proton-exchange membrane (PEM) applications. However, its practical applications have been limited by its relatively high dispersion in water, which usually occurs during the operation of proton-exchange membrane fuel cells (PEMFCs). In addition, the proton conductivity of bacterial cellulose is poor. In this study, functionalized BC modified with 3-aminopropyltriethoxysilane (APTES) was prepared using a solvent casting method to enhance its performance. The results showed that the water stability of the modified BC membrane was significantly improved, with the contact angle increasing from 54.9° to 103.3°. Furthermore, the optimum ratio of BC and APTES was used to prepare a proton-exchange membrane with a maximum proton conductivity of 62.2 mS/cm, which exhibited a power generation performance of 4.85 mW/cm2 in PEMFCs. It is worth mentioning that modified BC membranes obtained by combining an alkaline proton carrier (-NH2) with BC have rarely been reported. As fully bio-based conductive membranes for PEMFCs, they have the potential to be a low-cost, eco-friendly, and degradable alternative to expensive, ecologically problematic fluoric ionomers in short-term or disposable applications, such as biodegradable electronics and portable power supplies. [ABSTRACT FROM AUTHOR]

High-performance proton exchange membranes are of great importance for fuel cells. Here, we have synthesized polycarboxylate plasticizer modified MIL-101-Cr-NH2 (PCP-MCN), a kind of hybrid metal-organic framework, which exhibits a superior proton conductivity. PCP-MCN nanoparticles are used as additives to fabricate PCP-MCN/Nafion composite membranes. Microstructures and characteristics of PCP-MCN and these membranes have been extensively investigated. Significant enhancement in proton conduction for PCP-MCN around 55 °C is interestingly found due to the thermal motion of the PCP molecular chains. Robust mechanical properties and higher thermal decomposition temperature of the composite membranes are directly ascribed to strong intermolecular interactions between PCP-MCN and Nafion side chains, i.e., the formation of substantial acid-base pairs (-SO-<3 ···+H-NH-), which further improves compatibility between additive and Nafion matrix. At the same humidity and temperature condition, the water uptake of composite membranes significantly increases due to the incorporation of porous additives with abundant functional groups and thus less crystallinity degree in comparison to pristine Nafion. Proton conductivity (s) over wide ranges of humidities (30 - 100% RH at 25 °C) and temperatures (30 - 98 °C at 100% RH) for prepared membranes is measured. The s in PCPMCN/ Nafion composite membranes is remarkably enhanced, i.e. 0.245 S/cm for PCP-MCN-3wt.%/Nafion is twice that of Nafion membrane at 98 °C and 100% RH, because of the establishment of well-interconnected proton transport ionic water channels and perhaps faster protonation-deprotonation processes. The composite membranes possess weak humidity-dependence of proton transport and higher water uptake due to excellent water retention ability of PCP-MCN. In particular, when 3 wt.% PCP-MCN was added to Nafion, the power density of a single-cell fabricated with this composite membrane reaches impressively 0.480, 1.098 W/cm² under 40% RH, 100% RH at 60 °C, respectively, guaranteeing it to be a promising proton exchange membrane. [ABSTRACT FROM AUTHOR]

This study demonstrates a high‐throughput fabrication of fiber interlayers for proton exchange membranes based on poly(pentafluorostyrene) (PPFSt) and its aminated derivatives. The fibers are produced by electrospinning, where the parameters are carefully screened. The controlled parameters are solvent composition, weight percentage, voltage, flow rate, and temperature, controlled with a self‐designed heating jacket. The parameters are iterated toward optimized fiber structure and maximum output. The yielded fibers are infiltrated with Nafion and sulfonated polymer from bisphenol AF and decafluorobiphenyl (SFS001) by spray‐coating and doctor blading to obtain the fiber‐reinforced proton exchange membranes. Tensile tests reveal a higher Young's modulus and yield stress than pure Nafion. Here, the basicity of the aminated PPFSt fibers correlates with the Young's modulus due to improved acid‐base interactions between amine groups and sulfonic acid. The acid‐base interactions influence the composite membrane's proton conductivity, varying from 23 mS cm−1 for strongly alkaline fibers to 69 mS cm−1 for non‐basic fibers. These findings can be transferred to fabricating fiber reinforcements beyond routinely used poly(benzimidazoles). [ABSTRACT FROM AUTHOR]

Ammonia (NH₃) is a promising fuel for protonic ceramic fuel cells (PCFCs) due to its favorable liquefaction conditions and high volumetric energy density. However, even state-of-the-art PCFC anodes show insufficient NH₃ decomposition activity at reduced temperatures, compromising PCFC power output and durability. In this study, we report a novel nickel-perovskite-type structured oxide cermet anode with an NH₃ decomposition activity that enables relatively high power output from direct NH₃-PCFCs at 600 °C. We co-dope K and Mg into a perovskite-type structured oxide to produce the Ba 0.95 K 0.05 (Zr 0.1 Ce 0.7 Y 0.1 Yb 0.1) 0.95 Mg 0.05 O 3- δ (BZCYYb-KMg) material, which facilitates the rate-limiting steps in NH₃ decomposition: hydrogen transport and nitrogen desorption. Consequently, our modified nickel-perovskite-type structured oxide cermet anode achieves 100% NH₃ conversion at 600 °C. When used as a PCFC anode, this material increased the power output of a PCFC using NH₃ fuel at 600 °C by 25% and lifetime by more than 15 times compared to PCFC containing the unmodified nickel-perovskite-type structured oxide cermet anode. • The K and Mg co-doped BZCYYb (BZCYYb-KMg) shows increased proton conductivity and facilitates N 2 desorption from the nickel cermet. • Ni + BZCYYb-KMg shows a 100% NH 3 conversion rate at 600 °C. • Ni + BZCYYb-KMg increases the power output of PCFCs by 25% when used as an anode at 600 °C relative to the unmodified anode. • The reversible reaction between Ni and NH 3 significantly changes the anode morphology. [ABSTRACT FROM AUTHOR]

For reliable long-term operation of solid oxide electrochemical devices for the hydrogen energy system, an electrolyte with high ionic conductivity and excellent chemical stability is required. SrHfO 3 -based perovskites are known for their high chemical resistance; however, their ionic conductivity must be increased. In the present research, the effect of doping with yttrium and ytterbium on the electrical properties of strontium hafnate was studied for the first time. The crystal structure, solubility limit of the dopants, morphology and electrical properties of SrHf 1-x M x O 3-δ (M = Y, Yb) materials were investigated by the X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, direct current four-probe technique, and impedance spectroscopy. The solubility limits of Y and Yb in SrHfO 3 were found to lie slightly below x = 0.10. It was revealed that yttrium doping is more favorable for the grain growth and densification of ceramics. A comparative analysis of the influence of dopant type (Y, Yb and Sc) and concentration on the electrical properties of SrHfO 3 is provided. [Display omitted] • Homogeneity range of SrHf 1-x Y x O 3-δ and SrHf 1-x Yb x O 3-δ solid solutions extends to x ≈< 0.10. • Y-doping is more favorable for the grain growth and densification of ceramics. • Y and Yb-doping enhance proton conductivity of SrHfO 3. • Y-doped SrHfO 3 has higher ionic transference numbers in wet oxidizing atmospheres. [ABSTRACT FROM AUTHOR]

The search for novel functional ceramic materials with targeted properties is currently very important. Complex oxides with perovskite or perovskite-related structure are being considered for the production of electrochemical devices for the hydrogen energy ecosystem. Layered perovskites including based on BaLaInO 4 are promising materials for proton-conducting electrolyte of solid oxide fuel cells. The idea of this work is to create a triple conductivity material based on BaLaInO 4. In this work, the doping of the lanthanum sublattice with iron ions was carried out for the first time. The effect of doping on the structure, water uptake and electrical conductivity was investigated. It was shown that the introduction of iron ions into lanthanum sublattice changes the crystal lattice from orthorhombic to tetragonal structure. The water uptake is very small and it is 0.02 mol H 2 O per formula unit for BaLa 0.9 Fe 0.1 InO 4–δ composition. Studies of the electrical properties have shown that the nature of conductivity is mixed hole/oxygen ionic at dry air and hole/oxygen ionic/protonic and wet air. The Fe-doped-composition can be considered as triple conducting materials and it is prospective as the electrode materials comparable with protonic electrolyte Ba 1.1 La 0.9 InO 3.95. [ABSTRACT FROM AUTHOR]

The quest for sustainable energy solutions drives ongoing research into proton-conducting oxides, also known as protonic ceramics, which hold promise for revolutionizing electrochemical energy technologies. These materials exhibit unique proton conductivity at moderate temperatures, offering advantages over traditional electrolytes. Since Francis Forrat's mid-20th-century discovery of ceramic proton conduction, significant advancements have propelled the field forward, focusing on fuel cells, electrolysis cells, and other energy applications. Challenges persist, including poor electrode adhesion and the need for cost-effective fabrication methods. Recent studies explored cathode material design, innovative fabrication techniques like rapid laser reactive sintering, and theoretical simulations using density functional theory to understand proton migration mechanisms. This review discusses the properties, methodologies, innovations, applications, and future directions of proton-conducting oxide materials. By addressing existing challenges and exploring emerging opportunities, this review aims to contribute valuable insights to the evolving field of protonic ceramics as it continues to evolve. Scheme presentation. [Display omitted] • Overview of Proton-Conducting Oxide Materials: Defines, classifies, explains conduction, and explores applications. • Evaluates benefits and drawbacks of conventional synthesis methods. • Examines recent progress in creating high-performance materials using advanced methods and nanotech. • Investigates methods to enhance proton conductivity through interface engineering. • Assesses potential and obstacles in utilizing proton-conducting oxides for energy conversion and storage applications. [ABSTRACT FROM AUTHOR]

Hydrogen's significance as a clean and high-energy source spans various industries, driving advancements in fuel cell technology, transportation, and renewable energy storage systems. In particular, solid-state proton conductors like perovskite-type materials exhibit promising attributes for applications such as fuel cells and hydrogen sensors. However, conventional shaping techniques like uniaxial pressing impose limitations on device scalability and geometry. To address these challenges, alternative methods are gaining traction, like cold isostatic pressing or additive manufacturing. Each technique offers distinct advantages in shaping materials, impacting their structural and morphological properties. In this study, pellets of BaCe 0.6 Zr 0.3 Y 0.1 O 3-δ (BCZY) solid-state electrolyte were fabricated using four different shaping techniques: uniaxial pressing, cold isostatic pressing, 3D extrusion, and lithography. Characterization via X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy provided insights into changes in crystalline structure, sintering quality, and electrochemical properties, respectively. [Display omitted] • BCZY shaped via four methods: Uniaxial pressing, CIP, 3D extrusion and lithography. • XRD revealed slight unit cell reduction, with 3D printed samples having impurities. • DRT revealed five processes: bulk, grain boundary and three electrode's processes. • All elements showed similar bulk H+ conductivity, with Ea between 0.5 and 0.6 eV. • Impurities in lithography-shaped samples affected the total conductivity. [ABSTRACT FROM AUTHOR]

The search for new promising ceramic materials for various applications is an important task. In particular, ceramic materials are required as a part of electrochemical energy devices such as solid oxide fuel cells. Layered perovskites are promising materials for proton-conducting electrolyte of solid oxide fuel cells. In this article, samarium doped composition BaLa 0.9 Sm 0.1 InO 4 was obtained for the first time. The effect of doping on the structure, water uptake and ionic transport (O2− and H+) was investigated. It was shown that the samarium doping leads to the increase in conductivity values of up to 2 orders of magnitude. At low temperatures the proton transport numbers are 87–93 %, which indicates dominance of proton transfer. [Display omitted] [ABSTRACT FROM AUTHOR]

Proton-conducting solid-state electrolytes, including perovskite-type materials, hold promise for hydrogen sensor development. These sensors leverage the proton conductivity of such materials to detect hydrogen gas presence. However, achieving both high density for gas tightness and good protonic conductivity in these refractory materials can be challenging. In this study, we propose the preparation of dense pellets of BaCe 0.6 Zr 0.3 Y 0.1 O 3-δ using ZnO as a sintering aid (BCZY-Zn). These pellets were extensively characterized using X-ray diffraction and electrochemical impedance spectroscopy and compared with pellets sintered without sintering aid (BCZY). Subsequently, BCZY-Zn electrolyte was utilized to fabricate amperometric sensors for hydrogen monitoring. Finally, amperometric measurements were conducted at 500 °C while maintaining a voltage of 150 mV between electrodes. The sensors' performance was evaluated for hydrogen partial pressures ranging from 12 to 100 Pa within an argon atmosphere. Additionally, response and recovery times were calculated. [Display omitted] • XRD showed smaller lattice parameters for BCZY-Zn (4.3410 Å) than for BCZY (4.3450 Å). • Bulk, grain boundary and three electrode processes were identified in EIS. • Bulk conductivity's activation energy was mostly unaffected by ZnO. • ZnO enhanced pellet densification, reducing the activation energy. • BCZY-Zn had good sensitivity and response and recovery times from 12 to 100 Pa. [ABSTRACT FROM AUTHOR]

Using mechanical activation of an oxide mixture containing 0.2 wt% hexagonal boron nitride, followed by high-temperature firing (1400–1500 °C), we prepared single-phase (La 0.2 Nd 0.2 Ho 0.2 Lu 0.2 Y 0.2) 2 ZrO 5 ceramic, a high-entropy oxide (HEO) analog of Gd 2 ZrO 5 , whereas we failed to obtain single-phase Gd 2 ZrO 5 under similar conditions: the material consisted of two phases, with the fluorite and bixbyite structures, like in the case of conventional synthesis or coprecipitation in previous work. Thus, the use of the HEOs allowed us to obtain a phase-pure compound with the fluorite structure at a markedly lower synthesis temperature. An important role was played by 0.2 wt% hyperstoichiometric hexagonal BN additions, which ensured considerable amorphization of the starting oxides. The start powders and resulting ceramics were studied by X-ray diffraction, SEM analyses and conductivity was measured by impedance spectroscopy method in dry and wet air. The highest proton conductivity, ∼2.5 × 10−5 S/cm at 630 °C, was offered by the (La 0.2 Nd 0.2 Ho 0.2 Lu 0.2 Y 0.2) 2 ZrO 5 HEO ceramic. The use of HEO analogs of various compounds can be helpful for not only assessing thermodynamic properties of ceramics (reduction in synthesis and polymorphic transformation temperatures), but also preparing proton conductors when it is necessary to enhance hydrating properties of the cation sublattice. [ABSTRACT FROM AUTHOR]

Many proton-conducting oxides are refractory, making it difficult to fabricate dense electrolyte membranes for electrochemical devices. The use of a sintering additive is a common strategy, although it often has a negative effect on proton transport. We found that the addition of ZnO (2 and 4 mol%) successfully contributes to densification of SrHf 0.8 Sc 0.2 O 3-δ ceramics at 1450 °C without negative consequences for the ionic transport. The chemical stability of the materials, high levels of hydration and proton conductivity were confirmed. ZnO is partially (less than 0.3 mol%) incorporated into the crystal lattice of the perovskite and partially accumulates at grain boundaries gradually volatilizing during high-temperature treatments. As a result, ZnO sintering additive does not influence the bulk and specific grain-boundary conductivities, ionic transference numbers and hydration ability, maintaining the excellent electrolytic properties of SrHf 0.8 Sc 0.2 O 3-δ ceramics. [ABSTRACT FROM AUTHOR]

The solid solution Ba 5 In 2– x Y x Al 2 ZrO 13 (0 ≤ х ≤0.50) with hexagonal structure (space group P 6 3 / mmc) was prepared by the solid-state reaction method. The effects of isovalent Y3+-substitution on the structure, hydration, bandgap and transport properties have been investigated. The introduction of yttrium was accompanied by lattice expansion, which led to an increase in the concentration of protons during hydration. The doping did not lead to a significant increase in oxygen-ion conductivity since there was no change in oxygen stoichiometry. At the same time, doping led to an increase in ionic transport numbers due to a decrease in hole conductivity. Proton conductivity contribution and the values of proton conductivity increase with the increase in yttrium concentration. The phases with yttrium content x > 0.2 were predominant proton conductors at the temperature below 600°С under wet air. [ABSTRACT FROM AUTHOR]

Recently it was found that doped barium stannates have proton conductivity and can be used for various electrochemical applications. In this study, we investigated the effect of lutetium doping of the tin sublattice on the functional performance of oxides BaSn 1-х Lu х O 3 (х = 0, 0.05, 0.1, 0.15). Oxides with the concentration of lutetium up to 10% mol. were found to be single-phase, crystallizing in a cubic structure with a space group Pm 3 m. The lattice parameter increases linearly with the concentration of lutetium. The oxide with 15 % mol. of lutetium contains an additional phase of Lu 2 Sn 2 O 7. Electrical conductivity of the oxides was studied by the 4-probe DC method and impedance spectroscopy. Experiments were carried out in H 2 O and D 2 O - containing air atmospheres, as well as under dry air conditions. It was found that electrical conductivity of BaSnO 3 does not depend on humidity, while for Lu-doped oxides tends to decrease with increase in the humidity. Impedance data analysis has shown that change in the humidity mostly affects the grain boundary resistance. It is shown for the first time that the conductivity of BaSn 1-х Lu х O 3-δ in D 2 O-containing air is higher than in H 2 O-containing air, which was explained by the thermodynamic isotope effect. [ABSTRACT FROM AUTHOR]

The significant role of the cathodic binder in modulating mass transport within the catalyst layer (CL) of fuel cells is essential for optimizing cell performance. This investigation focuses on enhancing the membrane electrode assembly (MEA) through the utilization of a short‐side‐chain perfluoro‐sulfonic acid (SSC‐PFSA) ionomer as the cathode binder, referred to as SSC‐MEA. This study meticulously visualizes the distinctive interpenetrating networks of ionomers and catalysts, and explicitly clarifies the triple‐phase interface, unveiling the transport‐friendly microstructure and transport mechanisms inherent in SSC‐MEA. The SSC‐MEA exhibits advantageous microstructural features, including a better‐connected ionomer network and well‐organized hierarchical porous structure, culminating in superior mass transfer properties. Relative to the MEA bonded by long‐side‐chain perfluoro‐sulfonic acid (LSC‐PFSA) ionomer, noted as LSC‐MEA, SSC‐MEA exhibits a notable peak power density (1.23 W cm−2), efficient O2 transport, and remarkable proton conductivity (65% improvement) at 65 °C and 70% relativity humidity (RH). These findings establish crucial insights into the intricate morphology‐transport‐performance relationship in the CL, thereby providing strategic guidance for developing highly efficient MEA. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It includes the titles and authors of various articles published in the journal, covering topics such as crystal engineering, nonmetallic ion storage, nitrate reduction, and catalytic activity of metal complexes. The journal is published by The Royal Society of Chemistry, a leading chemistry community. [Extracted from the article]

Post-synthetic modification of proton-conducting metal–organic frameworks (MOFs) by loading small molecules capable of generating protons into pores is an efficient approach for developing a new type of material with improved ionic conductivity. Herein, the synthesis, characterization and proton conductivity of a novel electroneutral MOF based on palladium(II) meso-tetrakis(4-(phosphonatophenyl))porphyrinate, IPCE-1Pd, are reported. The exposure of the obtained framework to imidazole by the diffusion vapor method has surprisingly led to its complete crystal-to-crystal MOF-to-HOF transformation, resulting in the formation of a novel hydrogen-bonded organic framework (HOF) IPCE-1Pd_Im, which is the first example of such kind of structural change among all known MOFs. This modification has led to an almost 25-fold increase in the proton conductivity in comparison with the pristine MOF, reaching up to 6.54 × 10−3 S cm−1 at 85 °C and 95% relative humidity, which is one of the highest values among all known porphyrin-based HOFs. [ABSTRACT FROM AUTHOR]

A case of organic–inorganic hybridized phosphotungstate modified using aromatic organophosphonic acid, K4Na4H11[KCo2(H2O)10P4W24O92{(PhPO)2}]·48H2O (1), was successfully synthesized in conventional aqueous solution. The prominent structural feature is that the total structure of [KP4W24O92{(PhPO)2}]23− resembles a V-shaped structure, which was stabilized by two [Co(H2O)5]2+ ions. Furthermore, it can be connected into a three-dimensional mesh structure using K+ ions. Surprisingly, 1 possesses a remarkably high proton conductivity of 1.59 × 10−2 S cm−1 at 95% RH and 318 K probably due to the fact that its structure contains large amounts of lattice water molecules, coordination water molecules and counter cations. [ABSTRACT FROM AUTHOR]

Herein, a novel ionic hydrogen-bonded organic framework (iHOF-12) was synthesized. The 5-fold interpenetrating network structure and charge-assisted synergistic effects enable iHOF-12 to maintain robustness under demanding conditions and attain excellent proton conductivity of 1.23 × 10−2 S cm−1, which contributes to the enhancement of the DMFC performance. [ABSTRACT FROM AUTHOR]

A membrane with a low methanol permeability and high proton conductivity (σ p) is essential for the effective operation of a direct methanol-based fuel cell. Herein, a bio-metal organic framework was prepared with natural α-amino acids as ligands and then combined with hydrolyzed polyacrylonitrile (PAN) nanofibers (AA-MOF@PAN). The resulting nanocomposite membranes were subsequently integrated into a Nafion matrix (AA-MOF@PAN/Nafion). The –NH 2 groups on AA-MOF@PAN interact with –SO 3 H groups on Nafion, forming long-range acid-base pairs along the interface between the matrix and nanofibers. This interaction creates abundant proton-conducting sites for proton exchange membrane. Notably, the AA-MOF@PAN-4h/Nafion membrane demonstrated an exceptional proton conductivity (σ p) of 0.25 S cm−1 and a higher power density of 117.61 mW cm−2 compared to the recast Nafion membrane. This study offers valuable insights into the three-dimensional ordered design of a natural α-amino acids as a proton transfer sites and highlighting their potential applications in proton exchange membranes. • In situ growth of uniformly distributed AA-MOF onto hydrolyzed PAN nanofiber. • AA-MOF@PAN were introduced as proton-conducting channels. • AA-MOF@PAN-4h/Nafion exhibited the highest proton conductivity of 0.25 S cm−1 at 80 °C. • Introduction of AA-MOF@PAN resulted in a reduced fuel crossover. [ABSTRACT FROM AUTHOR]

The relationship between the mechanical, electrical, and morphological properties of annealed films based on short-side-chain perfluorinated sulfonic acid ionomer (SSCI) with an Aquivion structure was systematically investigated using dynamic mechanical analysis (DMA), small-angle X-ray scattering (SAXS), and impedance spectroscopy. Annealing the membranes at temperatures of 140, 150, and 160 °C—above the glass transition temperature of SSCI—and the nature of the liquid phase in the polymer dispersion significantly influence the structural parameters of the membranes, specifically the size of the conductive channels formed by hydrophilic sulfonic acid groups. SAXS and AFM analyses revealed that membranes cast from N,N-dimethylacetamide (DMAA) exhibit a denser, less structured morphology, resulting in lower hydrogen permeability (φ = 4.6 ± 0.7 nmol/m/s/MPa), comparable to the commercial Nafion 211 membrane (φ = 6.5 nmol/m/s/MPa), but with significantly lower proton conductivity (35 ± 5 mS/cm) than Nafion 211 (95 mS/cm). In contrast, membranes obtained from a water-alcohol mixture showed a well-defined structure (SAXS, AFM), with proton conductivity values ranging from 70 to 103 mS/cm, comparable to Nafion 211. However, the hydrogen permeability of these membranes varied significantly depending on the annealing conditions (φ = 5.5–65.3 nmol/m/s/MPa). SAXS data indicated that the membranes had a similar degree of crystallinity (11–13%) but differed in the positions of the ionomer peak and matrix knee, which are associated with variations in the size of the conductive channels and account for the observed differences in ionic conductivity. Membranes annealed at 150 °C, which exhibited hydrogen permeability and ionic conductivity values close to those of the commercial Nafion 211 membrane, were used to fabricate membrane electrode assemblies (MEA). The electrochemical characteristics of these MEAs were investigated at 30 and 60 °C, 100% relative humidity, at both atmospheric pressure and 200 kPa overpressure. At a current density of 1.75 A/cm2, the fabricated membranes demonstrated power outputs of up to 550 and 950 mW/cm2, which are comparable to, and even exceed, those of the commercial Nafion 211 membrane (700 mW/cm2). However, despite the high-power performance, significant membrane degradation was observed after 10,000 cycles in durability tests. These findings contribute to a better understanding of the relationship between the electrochemical properties and the structure of short-side-chain perfluorinated sulfonic acid ionomers with an Aquivion-type structure and are expected to enhance their application in fuel cells. [Display omitted] • The effect of annealing temperature on PFSA films properties has been studied. • Films based on dispersion ROH/H 2 O and DMAA differ in ionic conductivity. • MEA based on films annealed at 150 °C shown power density up to 950 mW/cm2. [ABSTRACT FROM AUTHOR]

Proton-conducting ceramic materials have emerged as effective candidates for improving the performance of solid oxide cells (SOCs) and electrolyzers (SOEs) at intermediate temperatures. BaCeO3 and BaZrO3 perovskites doped with rare-earth elements such as Y2O3 (BCZY) are well known for their high proton conductivity, low operating temperature, and chemical stability, which lead to SOCs' improved performance. However, the high sintering temperature and extended processing time needed to obtain dense BCZY-type electrolytes (typically > 1350 °C) to be used as SOC electrolytes can cause severe barium evaporation, altering the stoichiometry of the system and consequently reducing the performance of the final device. The cold sintering process (CSP) is a novel sintering technique that allows a drastic reduction in the sintering temperature needed to obtain dense ceramics. Using the CSP, materials can be sintered in a short time using an appropriate amount of a liquid phase at temperatures < 300 °C under a few hundred MPa of uniaxial pressure. For these reasons, cold sintering is considered one of the most promising ways to obtain ceramic proton conductors in mild conditions. This review aims to collect novel insights into the application of the CSP with a focus on BCZY-type materials, highlighting the opportunities and challenges and giving a vision of future trends and perspectives. [ABSTRACT FROM AUTHOR]

[Display omitted] Proton exchange membranes (PEMs) applied in fuel cell technology suffer from the trade-off between fast proton conduction and durable operation involving dimensional stability, mechanical strength, and oxidative resistance. To address this issue, a novel branched polybenzimidazole (brPBI) was synthesized, covalently cross-linked with (3-chloropropyl)triethoxysilane (CTS), and doped with a novel proton conductor FeATMP to prepare brPBI-CTS/FeATMP membranes. The branching degree of brPBI was optimized to achieve high molecular weight while the branching structure offered high free volume, abundant end-groups, and self-cross-linking moiety that enhanced proton conduction and dimensional/mechanical/oxidative stability. Covalent cross-linking with CTS enhanced the dimensional, mechanical, and oxidative stability while improving the water-assisted proton conduction owing to the hydrophilic nature of siloxane structure formed. At 180 ℃, the proton conductivity of the brPBI3-CTS/FeATMP composite membrane reached 0.136, 0.073, and 0.041 S cm−1 at 100 % RH, 50 % RH, and 0 % RH, respectively, while its swelling ratio after immersion in water at 90 ℃ for 24 h was 4.69 %. The performance of the membranes demonstrated that construction of hydrophilic structure by covalent cross-linking was a successful strategy to break the trade-off effect for PEMs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu2+-chelated SPEEK membrane with high IEC is prepared. • High mechanical and dimensional stability are observed for SPEEK-Cu membrane. • Proton conductivity of SPEEK-based membranes reaches 0.074 S/cm at −25 °C. • Water states of samples at subzero temperatures are quantified via DSC analysis. • SPEEK-Cu membrane possesses a stronger anti-freezing property. Improving the proton conductivity (σ) of proton exchange membranes at low temperatures is very important for expanding their application areas. Here, sulfonated poly ether ether ketone (SPEEK) membranes were prepared with different sulfonation degrees, and its maximum ion exchange capacity is 3.15 mmol/g for 10 h at 60 °C. Highly sulfonated SPEEK membrane exhibits ultra-high water uptake and excellent proton conductivity of 0.074 S/cm at −25 °C due to its abundant −SO 3 H. Nevertheless, its high swelling ratio and low mechanical strength are not conducive to the practical application of the membrane. Luckily, by employing the chelation of Cu2+ with −SO 3 − on the SPEEK chain, Cu2+-coordinated SPEEK membranes were prepared, and they not only retain high −SO 3 H content but also possess robust mechanical properties and good dimensional stability compared to pristine SPEEK membrane. Meanwhile, the σ of the SPEEK-Cu membrane reaches 0.054 S/cm at −25 °C, and its fuel cell maximum power (W max) reaches 0.42 W/cm2 at −10 °C, demonstrating superior low-temperature performance in comparison to other reported materials. Particularly, water states in the prepared membranes are quantified by low-temperature differential scanning calorimetry. Because much more water bound to the plentiful −SO 3 H and Cu2+ inside the membrane endows it with anti-freezing performance, the decay of the σ and the W max for the SPEEK-Cu membrane is retarded at sub-zero temperatures. It is envisioned that composite membranes comprising metal ions such as Cu2+-SPEEK have a high potential for sub-zero fuel cell applications. [ABSTRACT FROM AUTHOR]

Using highly sulfonated poly(ether ether ketone) (SPEEK) as the base material, the structure and properties of poly(ether ether ketone) (PEEK) membranes are optimized by precisely controlling the doping of phosphotungstic acid (HPW), dopamine (DA), and various amounts of carbon nanomaterials. Compared with conventional PEEK membranes, this optimized membrane exhibits higher proton conductivity, lower water absorption swelling rate, and excellent thermal stability. Highly SPEEK is soluble in water, thus fails to be used in fuel cell applications. Herein, we conduct Friedel‐Crafts method to obtain cross‐linked highly sulfonated membrane with controlled water uptake and swelling while still maintaining high proton conductivity. The polymer is then doped with phosphotungstic acid (HPW) to acquire enhanced performance. To control HPW leakage, polydopamine (PDA) acting as double‐sided adhesive is incorporated within the membrane. By distributing 1 wt.% PDA, the HPW leakage is reduced almost three times. The composite C‐SPEEK/HPWx/PDAy membranes have exhibited excellent overall performance. Specifically, the best proton conductivity result of C‐SPEEK/HPW50 has reached 0.271 S/cm. Moreover, it has presented superb performance in H2/O2 single cell test recorded as power density of 886.13 mW/cm2 while current density is 1614.20 mA/cm2 at 60°C. [ABSTRACT FROM AUTHOR]

In this work, a novel type of fluorine‐lean proton exchange membranes is presented, using sulfonamide‐sulfonimide functional groups for ion conduction. These groups are constructed on a polystyrene backbone for simple and cost‐efficient usage as well as rapid scalability. The polymer is further tailored by adjusting the sulfonamide functionality with various end‐groups, namely pentafluorophenyl, 4‐fluorophenyl, butyl and octyl groups. These groups affect the pKa, leading to pKa values of 5.7 for the pentafluorophenyl substitution and pKa 10.5 for the alkyl chain. The glass transition temperature of the sulfonamide homopolymers can be reduced from Tg=151 °C (Pentafluorophenyl) to 49 °C (Octyl), making the ionomer more flexible at room temperature. The combination of the non‐swelling sulfonamide further mitigates the high water uptake of the sulfonimide while maintaining the nominal ion exchange capacity. This combination leads to extremely high proton conductivities with up to σ=283 mS cm−1 at room temperature, which is clearly outperforming Nafion and approaches values for acid doped systems. This approach can pave the way to a novel type of ion conducting class in proton exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) have proven to be a promising power source for various applications ranging from portable devices to automotive and stationary power systems. The production of PEMFC involves numerous stages in the value chain, with each stage presenting unique challenges and opportunities to improve the overall performance and durability of the PEMFC stack. These include steps such as manufacturing the key components such as the platinum‐based catalyst, processing these components into the membrane electrode assemblies (MEAs), and stacking the MEAs to ultimately produce a PEMFC stack. However, it is also known that the break‐in or conditioning phase of the stack plays a crucial role in the final performance as well as durability. It involves several key phenomena such as hydration of the membrane, swelling of the ionomer, redistribution of the catalyst and the creation of suitable electrochemical interfaces – establishment of the triple phase boundary. These improve the proton conductivity, the mass transport of reactants and products, the catalytic activity of the electrode and thus the overall efficiency of the FC. The cruciality of break‐in is demonstrated by the improvement in performance, which can even be over 50 % compared to the initial state. The state‐of‐the‐art approach for the break‐in of MEAs involves an electrochemical protocol, such as voltage cycling, using a PEMFC testing station. This method is time‐consuming, equipment‐intensive, and costly. Therefore, new, elegant, and cost‐effective solutions are needed. Nevertheless, the primary aim is to achieve maximum/optimal performance so that it is fully operational and ready for the market. It is therefore essential to better understand and deconvolute these complex mechanisms taking place during break‐in/conditioning. Strategies include controlled humidity and temperature cycling, novel electrode materials and other advanced break‐in methods such as air braking, vacuum activation or steaming. In addition, it is critical to address the challenges associated with standardisation and quantification of protocols to enable interlaboratory comparisons to further advance the field. [ABSTRACT FROM AUTHOR]

Metal organic framework (MOF) materials have attracted widespread attention due to their tunable structure, high porosity, and large specific surface area. MOF modified with functional groups were introduced into ionic polymers that could provide proton conduction, which could prepare proton exchange membranes with high proton conductivity. In this paper, UiO-66-NH2 were introduced into sulfonated polyphosphazene (SPFPP) to prepare composite proton exchange membranes, the thermal stability, swelling degree, water uptake, and proton conductivity were characterized. Composite membranes exhibits excellent thermal stability, the swelling degree of the composite membranes are lower than that of the pure SPFPP membrane. UiO-66-NH2 could improve the water retention capacity of composite membranes, resulting in higher water uptakes of composite membranes than pure SPFPP membranes. This higher water retention capacity could improve the proton conductivity of the membrane under high humidity conditions. The proton conductivity of composite membranes SP/UiO-66-NH2 -0. 6 reaches up to 0. 179 S/cm under 80 ℃, 100% RH, while the proton conductivity of pure SPFPP membranes is 0. 120 S/cm under the same conditions. [ABSTRACT FROM AUTHOR]

This review discusses the progress of research on sulfonated poly(ether ether ketone) (SPEEK) and its composite membranes in proton exchange membrane fuel cells (PEMFCs). SPEEK is a promising material for replacing traditional perfluorosulfonic acid membranes due to its excellent thermal stability, mechanical property, and tunable proton conductivity. By adjusting the degree of sulfonation (DS) of SPEEK, the hydrophilicity and proton conductivity of the membrane can be controlled, while also balancing its mechanical, thermal, and chemical stability. Researchers have developed various composite membranes by combining SPEEK with a range of organic and inorganic materials, such as polybenzimidazole (PBI), fluoropolymers, and silica, to enhance the mechanical, chemical, and thermal stability of the membranes, while reducing fuel permeability and improving the overall performance of the fuel cell. Despite the significant potential of SPEEK and its composite membranes in PEMFCs, there are still challenges and room for improvement, including proton conductivity, chemical stability, cost-effectiveness, and environmental impact assessments. [ABSTRACT FROM AUTHOR]

PEMFCs play a key role in the energy transition scenarios thanks to the zero emissions, versatility, and power density. PEMFC performances are improved optimizing water management to ensure proper ion transport: it is well known that a well-balanced water content avoids either electrodes flooding or membrane drying, causing gas starvation at the active sites or low proton conductivity, respectively. In this paper, an analytical formulation for water transport dynamics within the membrane, derived from membrane water balance, is proposed to overcome the limitations of PEM dynamics model largely adopted in the literature. The dynamics is simulated thanks to the introduction of a characteristic time with a closed analytical form, which is general and easily implementable for any application where both low computational time and high accuracy are required. Furthermore, the net water molar fluxes at the membrane boundaries can be easily computed as well for a cell's simulation. The analytical formulation has a strong dependency on the operative conditions, as well as physical parameters of the membrane itself. From the proposed formulation, for a 200 µm membrane, the characteristic time can vary from 5 s up to 50 s; this example shows how control strategies must consider PEM dynamic behavior. [ABSTRACT FROM AUTHOR]

Proton-conducting solid oxide fuel cells (P-SOFCs) are widely studied for their lower working temperatures than oxygen-ion-conducting SOFCs (O-SOFCs). Due to the elevated preparation and operation temperatures varying from 500 °C to 1500 °C, high mechanical stresses can be developed in the electrolytes of SOFCs. The stresses will in turn impact the electrical conductivities, which is often omitted in current studies. In this work, the mechanical–conductive behaviors of Y-doped BaZrO3 (BZY) electrolytes for P-SOFCs under high temperatures are studied through molecular dynamics modeling. The Young's moduli of BZY in fully hydrated and non-hydrated states are calculated with different Y-doping concentrations and at different temperatures. It is shown that Y doping, oxygen vacancies, and protonic point defects all lead to a decrease in the Young's moduli of BZY at 773 K. The variations in the conductivities of BZY are then investigated by calculating the diffusion rates of protons in BZY at different triaxial, biaxial, and uniaxial strains from 673 K to 873 K. In all cases, the diffusion rate present a trend of first increasing and then decreasing from compression state to tension state. The variations in elementary affecting factors of proton diffusion, including hydroxide rotation, proton transfer, proton trapping, and proton distribution, are then analyzed in detail under different strains. It is concluded that the influences of strains on these factors collectively determine the changes in proton conductivity. [ABSTRACT FROM AUTHOR]

Solid‐state proton conductors with high conductivity at intermediate temperatures (100–300 °C) have recently gained attention due to their potential for a wide range of new electrochemical applications. The proton conductivity of cesium hydroxide hydrate (CsOH.H2O) is reported on, a superprotonic conductor whose ionic conductivity is hitherto unreported. Via a thermal treatment, the hexagonal and tetragonal CsOH.H2O phases are prepared and the effect of the degree of hydration (H2O content) on the structure and proton conductivity is investigated. It is shown that the temperature in the thermal treatment has an enormous influence on the structure and water content, and consequently, the proton transport. The conductivity of the hexagonal and tetragonal phases exceeds 3 × 103 S cm−1 at 30 °C and 10−2 S cm−1 at 120 °C, making them potentially suitable for both low‐ and intermediate‐temperature electrochemical applications. 1H NMR spin‐lattice relaxation rate measurements reveal fast dynamic processes with rates reaching the GHz regime, resulting in diffusion coefficients as high as 1.3 × 10−11 m2 s−1 at 60 °C, in good agreement with the proton conductivity results derived from impedance spectroscopy. These findings will inspire the development of novel inorganic solid proton conductors based on hydroxide hydrates. [ABSTRACT FROM AUTHOR]

Herein, fluorescent conducting tautomeric polymers (FCTPs) are developed by polymerizing 2‐methylprop‐2‐enoic acid (MPEA), methyl‐2‐methylpropenoate (MMP), N‐(propan‐2‐yl)prop‐2‐enamide (PPE), and in situ‐anchored 3‐(N‐(propan‐2‐yl)prop‐2‐enamido)‐2‐methylpropanoic acid (PPEMPA). Among as‐synthesized FCTPs, the most promising characteristics in FCTP3 are confirmed by NMR and Fourier transform infrared (FTIR) spectroscopies, luminescence enhancements, and computational studies. In FCTP3, ─C(═O)NH─, −C(═O)N<, ─C(═O)OH, and ─C(═O)OCH3 subluminophores are identified by theoretical calculations and experimental analyses. These subluminophores facilitate redox characteristics, solid state emissions, aggregation‐enhanced emissions (AEEs), excited‐state intramolecular proton transfer (ESIPT), and conductivities in FCTP3. The ESIPT‐associated dual emission/AEEs of FCTP3 are elucidated by time correlated single photon counting (TCSPC) investigation, solvent polarity effects, concentration‐dependent emissions, dynamic light scattering (DLS) measurements, field emission scanning electron microscopy images, and computational calculations. The cyclic voltammetry measurements of FCTP3 indicate cumulative redox efficacy of ─C(═O)OH, ─C(═O)NH─/−C(═O)N<, ─C(─O─)═NH+─/─C(─O─)═N+, and ─C(═N)OH functionalities. In FCTP3, ESIPT‐associated dual‐emission enable in the selective detection of Cr(III)/Cu(II) at λem1/λem2 with the limit of detection of 0.0343/0.079 ppb. The preferential interaction of Cr(III)/Cu(II) with FCTP3 (amide)/FCTP3 (imidol) and oxidation/reduction of Cr(III)/Cu(II) to Cr(VI)/Cu(I) are further supported by NMR‐titration; FTIR and X‐ray photoelectron spectroscopy analyses; TCSPC/electrochemical/DLS measurement; alongside theoretical calculations. The proton conductivity of FCTP3 is explored by electrochemical impedance spectroscopy and I–V measurements. [ABSTRACT FROM AUTHOR]

Four alkaline earth metal-based compounds were synthesized under hydrothermal conditions, using BPTC (benzophenone-3,3′,4,4′-tetracarboxylate) as ligand, and are hereinafter referred to as M-BPTC (M = Mg, Ca, Sr, Ba). These compounds exhibit interesting structural diversity, variable chemical and thermal stability, as well as antimicrobial activity and proton conductivity. The Ca-BPTC (C17H13O12Ca) belongs to the triclinic crystal system, P-1 space group (a = 6.9330 Å, b = 9.8359 Å, c = 14.8717 Å, α = 78.351°, β = 81.043°, γ = 71.696°). The Sr-BPTC (C17H10O11Sr2) crystallized into an orthorhombic crystal system, Pbca space group (a = 6.9945 Å, b = 10.3767 Å, c = 47.882 Å and α = β = γ = 90°) and showed proton conduction up to 55 °C. The compound Ba-BPTC (C17H8O10Ba2) belongs to the triclinic crystal system, P-1 space group (a = 4.39030 Å, b = 11.9969 Å, c = 16.0108 Å, α = 71.6830°, β = 86.2360°, γ = 89.790°). The crystal structure of the compound of Mg2+ with BPTC was not elucidated. The calcium coordination polymer and magnesium compound showed antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa and antifungal activity against Candida albicans. [ABSTRACT FROM AUTHOR]

Ceramic proton conductors have the potential to lower the operating temperature of solid oxide cells (SOCs) to the intermediate temperature range of 400–600 °C. This is attributed to their superior ionic conductivity compared to oxide ion conductors under these conditions. However, prominent proton-conducting materials, such as yttrium-doped barium cerates and zirconates with specified compositions like BaCe1−xYxO3−δ (BCY), BaZr1−xYxO3−δ (BZY), and Ba(Ce,Zr)1−yYyO3−δ (BCZY), face significant challenges in achieving dense electrolyte membranes. It is suggested that the incorporation of transition and alkali metal oxides as sintering additives can induce liquid phase sintering (LPS), offering an efficient method to facilitate the densification of these proton-conducting ceramics. However, current research underscores that incorporating these sintering additives may lead to adverse secondary effects on the ionic transport properties of these materials since the concentration and mobility of protonic defects in a perovskite are highly sensitive to symmetry change. Such a drop in ionic conductivity, specifically proton transference, can adversely affect the overall performance of cells. The extent of variation in the proton conductivity of the perovskite BCZY depends on the type and concentration of the sintering aid, the nature of the sintering aid precursors used, the incorporation technique, and the sintering profile. This review provides a synopsis of various potential sintering techniques, explores the influence of diverse sintering additives, and evaluates their effects on the densification, ionic transport, and electrochemical properties of BCZY. We also report the performance of most of these combinations in an actual test environment (fuel cell or electrolysis mode) and comparison with BCZY. [ABSTRACT FROM AUTHOR]

In this paper, fluorite-type proton conductors La 1.9 In 0.1 Ce 2 O 7 , La 1.9 In 0.05 Sc 0.05 Ce 2 O 7 and La 1.9 Sc 0.1 Ce 2 O 7 (referred to as LCO-I, LCO-IS and LCO-S), were synthesized by the low-cost solid-state reaction method. The formation process and structure of single-doped LCO-I and LCO-S and co-doped LCO-IS were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrochemical performance was studied using alternating current electrochemical impedance spectroscopy (EIS). XRD results showed that the synthesized material had a fluorite structure, without any impurity phase. SEM micrographs showed that LCO-I, LCO-S and LCO-IS had a fairly dense grain. EDS analysis confirmed that the elemental composition of LCO-I, LCO-S and LCO-IS was evenly distributed and contained no impurities. LCO-IS exhibited superior conductivity among related materials, and the total conductivity of LCO-IS in oxygen was 9.49 × 10−3 S cm−1 at 800 °C. The effects of co-doping on bulk and grain boundary properties were analyzed using the distribution of relaxation time (DRT). The bulk and grain boundary conductivity of co-doped LCO-IS was higher than that of single-doped LCO-I and LCO-S. LCO-IS showed good proton conductivity. In the temperature range of 300–800 °C, the proton conductivity was 1.35 × 10−6–4.43 × 10−3 S cm−1. For LCO-I and LCO-IS electrolyte supported symmetric cells (Ag ǀ LCO-I (LCO-IS) ǀ Ag), their open circuit voltages were 0.99 V and 0.97 V, respectively, at 700 °C, and the power densities were 8.8 mW cm−2 and 9.34 mW cm−2. This demonstrates the potential of LCO-IS to be used in various devices as a proton-conducting electrolyte. • The electrochemical performance of La 2 Ce 2 O 7 -based proton conductors were improved by co-doping strategy. • The ion transference properties of La 1.9 In 0.1 Ce 2 O 7 and La 1.9 In 0.05 Sc 0.05 Ce 2 O 7 were analyzed by defect model. • The effect of In and Sc co-doping on the electrochemical performance of bulk and grain boundary in La 1.9 In 0.05 Sc 0.05 Ce 2 O 7 was analyzed by the analysis of relaxation time distribution (DRT). [ABSTRACT FROM AUTHOR]

PA-doped polybenzimidazole membranes dominate high-temperature proton exchange membranes (HT-PEMs), but the current membranes have poor PA uptake ability, which directly affects the operational efficiency and stability of fuel cells. In this work, it is proposed that a series of grafted polybenzimidazole membranes containing benzimidazole side chains were successfully prepared by grafting 2-chloromethyl benzimidazole to the backbone of poly (2,5-benzimidazole) (ABPBI) via nucleophilic substitution reaction. All these membranes exhibited excellent mechanical properties, oxidative stability, and thermal stability. The introduction of benzimidazole side chains not only increased the free volume of the membranes to store more PA but also added additional basic sites to form hydrogen bonds with PA molecules and constructed a dense hydrogen bonding network, which greatly enhanced the PA uptake of the membranes and accelerated the proton conduction to reduce the activation energy. The proton conductivity of the PA-doped g-ABPBI-50% membrane reached 0.122 S cm−1 at 180 °C under humidity-free conditions, while the peak power density of the PA-doped g-ABPBI-30% membrane was as high as 0.372 W cm−2 at 160 °C, which was 1.75 times higher than that of the pure ABPBI membrane. These results highlight the potential of this grafted membrane for high-temperature proton exchange membrane fuel cells (HT-PEMFCs) applications. [Display omitted] • The proton conductivity of the PA-doped g-ABPBI-50% membrane reached 0.122 S cm−1 at 180 °C under humidity-free conditions. • The introduction of benzimidazole side chains increased the free volume of the membranes to store more PA. • The peak power density of the PA-doped g-ABPBI-30% membrane reached 0.372 W cm−2 at 160 °C under humidity-free conditions. [ABSTRACT FROM AUTHOR]

A challenging task in solid oxide fuel cells (SOFCs) is seeking for an alternative electrolyte, enabling high ionic conduction at relatively low operating temperatures, i.e., 300–600 °C. Proton‐conducting candidates, in particular, hold a significant promise due to their low transport activation energy to deliver protons. Here, a unique hierarchical TiO2‐SrTiO3@TiO2 structure is developed inside an intercalated TiO2‐SrTiO3 core as "yolk" decorating densely packed flake TiO2 as shell, creating plentiful nano‐heterointerfaces with a continuous TiO2 and SrTiO3 "in‐house" interfaces, as well the interfaces between TiO2‐SrTiO3 yolk and TiO2 shell. It exhibits a reduced activation energy, down to 0.225 eV, and an unexpectedly high proton conductivity at low temperature, e.g., 0.084 S cm−1 at 550 °C, confirmed by experimentally H/D isotope method and proton‐filtrating membrane measurement. Raman mapping technique identifies the presence of hydrogenated HO─Sr bonds, providing further evidence for proton conduction. And its interfacial conduction is comparatively analyzed with a directly‐mixing TiO2‐SrTiO3 composite electrolyte. Consequently, a single fuel cell based on the TiO2‐SrTiO3@TiO2 heterogeneous electrolyte delivers a good peak power density of 799.7 mW cm−2 at 550 °C. These findings highlight a dexterous nano‐heterointerface design strategy of highly proton‐conductive electrolytes at reduced operating temperatures for SOFC technology. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Rapid dynamics and remarkable proton conduction induced by confined water in nanospaces have attracted much attentions from researchers, which is crucial for advancing the development of innovative proton conductors and deepening comprehension of proton and water transport mechanisms within biological systems. In this aspect, carbon nanotubes (CNTs) are frequently employed as a research platform. However, they possess certain limitations, such as their inherent electronic conductivity and extreme hydrophobicity, which can impede the accurate assessment and precise regulation of proton conduction. We herein prepared two 2D COFs with different hydrophilic fragment, and obtained maximum acid‐free proton conductivity of 3.04 × 10–4 S·cm–1 at 70 °C and 100% RH with Grotthuss type activation energy of 0.14 eV. This is mainly due to that the water molecules in the center of channel form strong hydrogen bonds, enhancing proton dissociation and guiding fast directional diffusion. [ABSTRACT FROM AUTHOR]

Solid solutions of rare earth titanates with high contents of rare earth oxides of up to 50-62% have been synthesized by the co-precipitation method and their structure, microstructure and conductivity in dry and wet air have been studied. Proton conductors have been found for the first time in solid solutions of rare earth titanates with a high content of Ln2O3 (>50%) with a nominal formula composition of (LnxTi1-x)4O8-2x (Ln = Yb, Er, Ho, 0.667 = x = 0.765). Among (LnxTi1-x)4O8-2x (Ln = Yb, Er, Ho, x = 0.684), (HoxTi1-x)4O8-2x (x = 0.684) showed the maximum conductivity in wet air. In this context, four additional compositions (HoxTi1-x)4O8-2x (x = 0.718, 0.734, 0.75, and 0.765) were synthesized in the holmium series. An increase in the holmium content leads to an increase in the proton transfer coefficients; at the same time, a more complex nature of the dependence of the conductivity under dry and wet atmospheres is observed. For the fluorite-like solid solution (HoxTi1-x)4O8-2x (0.701 = x = 0.765), the proton transfer coefficients were found to be ~0.9 in the range of 200-450 °C. As the temperature continues to rise, the proton conductivity decreases quite sharply and the transfer coefficient becomes as low as 0.3 at 700 °C. The increase in proton conductivity in the Yb-Er-Ho series is associated with an increase in the hydrophilic properties of rare earth cations. In the (HoxTi1-x)4O8-2x (x = 0.667 = x = 0.765) series, the conductivity in wet air was ~1 × 10-6 S cm-1 at 450 °C for most compositions. The conductivity of ceramics with x = 0.701 and 0.75 is about 2 times higher, which may be due to the optimal size of pyrochlore nanodomains in the fluorite matrix for x = 0.701 and the formation of pure fluorite for x = 0.75, respectively. [ABSTRACT FROM AUTHOR]

The rapid development of new proton conductors based on metallo-hydrogen-bonded organic frameworks (MHOFs) and rational regulation of their performance are highly desired for proton exchange membrane fuel cells. As we all know, hydrogen bonds are an indispensable part of proton conduction as conducting mediators. However, the effect of hydrogen bonds, especially the number of hydrogen bonds, on proton conductivity is not yet clear. Herein, we focus on clarifying the relationship between proton conductivity and the number of hydrogen bonds in MHOFs. To this end, two MHOFs with analogous host-framework structures and different hydrogen-bonded networks, [Ni(HCi)2(NH3)4] (Ni–Ci–NH3) and [Ni(HCi)2(H2O)4] (Ni–Ci–H2O) (H2Ci = 1H-indazole-5-carboxylic acid), were designed by controlling coordination states between the same metal ion and different hydrogen bond donors and act as targeting models to study their proton-conducting properties. Notably, Ni–Ci–NH3 shows a high proton conductivity of 6.22 × 10−4 S cm−1 for the powder sample at ∼97% relative humidity (RH) and 303 K, which is superior to that of Ni–Ci–H2O (1.62 × 10−4 S cm−1) under the same condition. The difference in proton conductivity at ∼97% RH is closely related to the number of hydrogen bonds, as evidenced by water adsorption, water contact angle and dielectric loss measurements. Furthermore, frequency- and temperature-varied dielectric constant curves indicate that their proton transfer processes follow the Grotthuss proton-hopping mechanism. Meanwhile, a good correlation between the number of hydrogen bonds and activation energy was obtained, i.e. the more the number of hydrogen bonds, the lower the activation energy. This work contributes to the further understanding of the essential role of hydrogen bonds in the proton conductivity and proton transfer mechanisms. [ABSTRACT FROM AUTHOR]

Organic π‐scaffolds are being envisaged for new‐age electron‐ and ion‐responsive materials that can accumulate electrons as well as transport proton. However, such systems are extremely rare as electron‐deficient scaffolds are unstable in aqueous solution. Here we detail the synthesis of a water‐stable core‐naphthalenediimide‐nitrobenzyl‐viologen based tetra‐cation, which accumulates up to eight‐electrons within an exceptionally narrow potential window of +0.05 V and −1.12 V. The supramolecular interactions and the ensuing ionic framework are tunable based on the three anions, e. g. Cl−, Br− and PF6−, that are investigated in this work. The ionic framework is formed and supported by a range of H‐bonds, in which, the nitro benzyl groups act as pillars connecting the 1D water‐tapes and the halide anions. The water molecules are hydrogen‐bonded with the halide anions and bestow a facile pathway for the proton conduction, with proton conductivity up to 3.19×10−3 S cm−1. In contrast, the ionic assembly formed by the lipophilic PF6− anions do not host the water tapes and consequently the proton conductivity is found to be four orders of magnitude lower. This is a unique example, whereby proton conductivity is realized and is tunable within a highly electron‐deficient, eight‐electron acceptor, water‐stable ionic supramolecular system. [ABSTRACT FROM AUTHOR]