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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]

Inorganic-organic composite proton exchange membranes (PEMs) are promising substitutes in proton exchange membrane fuel cells. To improve the compatibility between inorganic fillers and polyelectrolytes, along with alleviating filler aggregation, a series of composite PEMs incorporating both sulfonated titanium dioxide nanotubes (sTiNT) and graphitic carbon nitride nanosheets (g-C 3 N 4) into sulfonated poly (aryl ether sulfone) s (SPAES) have been prepared. The distinct morphology of sTiNT and g-C 3 N 4 , coupled with their respective sulfonic acids and amine/imine functionalities, endow the fillers with exceptional compatibility and dispersivity within SPAES. The obtained SPAES/sTiNT/g-C 3 N 4 membranes exhibit superior thermal, size and mechanical stability, robust oxidative resistance, together with high proton conductivity. The SPAES/sTiNT/g-C 3 N 4 (1/3) membrane particularly exhibits proton conductivity of 202 mS/cm and swelling below 10% (90 °C), a hydrogen fuel cell output of 512 mW/cm2 (80 °C), which is 1.6 times of the SPAES membrane. The results suggest the great potential of multi-filler compositing strategy for alternative PEMs exploration. [Display omitted] • Sulfoalkoxyl-functionalized titanium nanotubes (sTiNT) have been synthesized. • STiNT and g-C 3 N 4 nanosheets are co-doped into SPAES matrix to prepare PEMs. • 1D/2D fillers co-doped PEMs exhibit exceptional compatibility and dispersivity. • Enhanced dimensional stability and conductivity result from co-doping strategy. • SPAES/sTiNT/g-C 3 N 4 (1/3) has 1.2 times higher σ and 1.6 times better power output. [ABSTRACT FROM AUTHOR]

The ionic conductivity of proton exchange membranes (PEMs) directly determines the ohmic resistance of proton exchange membrane fuel cells (PEMFCs), which is largely dependent on the membrane's hydration level. The structural differences between reinforced composite membranes (RCMs) and homogeneous membranes lead to distinct relationships between their hydration levels and ionic conductivity. In this study, Gore788.12 and Nafion®117 were selected as representatives of RCMs and homogeneous membranes, respectively. Experiments were designed to achieve operational conditions using a temperature and humidity chamber, wherein the PEM was weighed at equilibrium to calculate water uptake and water content, while EIS was employed to measure the membrane's ionic resistance and subsequently determine its conductivity, and HFR was utilized to compare the ohmic impedance of MEAs composed of two kinds of membrane under varying temperature and humidity conditions. In this study, the impacts of water activity on water uptake, water content, and ionic conductivity of the reinforced membrane are quantitatively analyzed. The results show that RCMs exhibit lower water content and ionic conductivity compared to homogeneous membranes, particularly at high water activity. The RCMs demonstrate lower ionic resistance and reduce dependence on water activity, resulting in lower ohmic resistance in MEAs using reinforced membranes. An empirical equation for ionic conductivity as a function of water activity is derived from experimental data. The semi-empirical equation between water content and water activity is modified based on the theoretical study of membrane water absorption mode under different water activity. This study can provide valuable insights for optimizing steady-state PEMFC simulation models. [Display omitted] • Water content of PEM has an exponential relationship with water activity. • Ionic conductivity of PEM has a linear relationship with water content. • The conductivity and water content of RCMs are lower than homogeneous membranes. • The mathematical models of water content and ionic conductivity are modified. [ABSTRACT FROM AUTHOR]

Proton-conducting metal–organic frameworks (MOFs) have attracted tremendous attention for their promising application in proton-exchange membrane fuel cells. Water clusters play an extremely important role in the proton-conduction process and affect the proton conductivity of host materials. To date, the close-packing effect of water clusters within pores on proton conductivity due to the amorphous structure of commercial proton-exchange membranes is unclear. Herein, we prepared two crystalline MOFs containing different water clusters, namely, [Sm2(fum)3(H2O)4]·3H2O (Sm-fum-7H2O) and [Er2(fum)3(H2O)4]·8H2O (Er-fum-12H2O) (H2fum = fumaric acid), and regulated their proton conductivities by changing the water clusters. As expected, Sm-fum-7H2O showed a high proton conductivity of 6.89 × 10−4 S cm−1 at 333 K and ∼97% RH because of the close packing of the water clusters within the pores triggered by a lanthanide contraction effect, outperforming that of Er-fum-12H2O and some previously reported MOFs. Additionally, Sm-fum-7H2O and Er-fum-12H2O demonstrated high dielectric functions, reaching 2.22 × 103 and 1.42 × 105 at 102.5 Hz, respectively, making Er-fum-12H2O a highly dielectric material. More importantly, broadband dielectric spectroscopy measurements indicated that there was a dielectric relaxation process in Er-fum-12H2O with an activation energy of 0.59 eV. The present findings provide a better understanding of the crucial role of confined water clusters in proton conductivity and the novel phenomenon of the coexistence of proton conduction and dielectric relaxation in crystalline MOF materials. [ABSTRACT FROM AUTHOR]

The design and development of cost-effective and increased methanol permeable and proton-conductive membranes are critical concerns in the fabrication of polymeric electrolyte membranes (PEM). A solution-casting process was used to create a low-cost PEM based on sulfonated polyvinyl chloride (SPVC)-Polymethyl methacrylate (PMMA) blended with varying concentrations of Poly(sodium 4-styrenesulfonate) (PSS). The contact angle, oxidative stability, swelling ratio, water uptake, and methanol uptake of SPVC/PMMA/PSS membranes were investigated as a function of PSS molar ratio. FT-IR examination, 1H NMR spectra, Raman spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscope micrographs were additionally utilized for confirming the chemical structure, morphology, and thermal stability of SPVC/PMMA/PSS membranes. Furthermore, the ion exchange capacity (IEC), proton conductivity, and methanol permeability of SPVC/PMMA/PSS membranes were investigated depending on the PSS concentration. The results showed a significant increase in proton conductivity from 1.80 × 10–2 for SPVC/PMMA/1%PSS to 4.7 × 10–2 S/cm for SPVC/PMMA/5%PSS at ambient temperature. On the other hand, the methanol permeability (P = 8.53 × 10–8 cm2/s) was noticeably lower than that of Nafion 117 (3.39 × 10–6 cm2/s). Additionally, the IEC of the manufactured membrane was 1.38 ± 0.7 meq g−1 for SPVC/PMMA/5%PSS compared to 0.91 meq g−1 for Nafion 117 membranes. The maximum water uptake of the synthesized membranes was 48.37 ± 2.27%, whereas Nafion 117 membrane absorption was 65.44%. According to conductivity studies and the membrane efficiency factor, the ideal PSS content in a polymer matrix is 4 wt.%. Finally, the developed SPVC/PMMA/PSS polyelectrolytic membranes show improvements in essential properties such as methanol permeability, proton conductivity, and IEC when combined with low-cost materials, making them an attractive contender as PEM for DMFCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of novel polymeric ionic liquids by introducing quaternary ammonium groups into cross-linkable ionic liquids. • Introduction of polymeric ionic liquids containing quaternary ammonium groups for the preparation of novel high-temperature proton exchange membrane materials. • The proton conductivity of OPBI-PIL-30 % membrane at 180 °C was 113.94 mS cm−1. • The phosphoric acid retention of the OPBI-PIL-30 % membrane reached 86.89 % after 240 h of testing at 160 °C in anhydrous environment. • After immersion in Fenton's reagent (3 % H 2 O 2 , 4 ppm FeSO 4) for 144 h, the proton conductivity of the OPBI-PIL-30 % membrane was 135.35 mS cm−1. • OPBI-PIL-20 % combines both excellent proton conductivity and mechanical properties, obtaining the highest peak power density of 436.19 mW cm−2 at 160 ℃. A series of membrane materials suitable for high-temperature proton exchange membranes (HT-PEM) were successfully prepared by introducing polymeric ionic liquids (PILs) containing quaternary ammonium groups into ether-bonded polybenzimidazole (OPBI). The structure of the cross-linked membrane has a strong interaction with phosphoric acid (PA), which enhances proton transport and PA retention. To ensure better overall performance of the cross-linked membrane, the optimal PIL content is 30 wt% (OPBI-PIL-30 %). The PA uptake of OPBI-PIL-30 % membrane was 323.24 %, and the proton conductivity at 180 ℃ was 113.94 mS cm−1, which was much higher than that of OPBI membrane. It is noteworthy that the PA retention of OPBI-PIL-30 % membrane could reach 71.38 % after 240 h of testing under the harsh environment of 80 ℃/40 % RH. The membrane showed better acid retention capacity of 86.89 % at 160 ℃ under anhydrous environment. The OPBI-PIL-20 % membrane achieved the maximum power density of 436.19 mW cm−2, attributed to its favorable mechanical characteristics and proton conductivity. By these excellent properties, it is shown that OPBI-PIL-X membranes containing quaternary ammonium groups have the potential to be applied in high temperature proton exchange membrane fuel cells (HT-PEMFCs). [ABSTRACT FROM AUTHOR]

Sulfonated poly (ether ether ketone) (SPEEK) has received substantial attention for its potential to improve the electrochemical behavior and thermomechanical capabilities of direct methanol fuel cells. This study examines how the integration by solution casting of microcrystalline cellulose (MCC) and 2,3-dialdehyde cellulose (DAC) onto highly sulfonated PEEK (with a sulfonation degree of 80%) affects its physicochemical properties and morphological structures. The mechanical attributes and proton conductivity of the polymer matrix are impacted by MCC and DAC inclusion into SPEEK membrane. The maximum proton conductivity was seen in the SPEEK/MCC membranes at 70 °C (up to 0.1 S cm−1). The proton conductivity in methanol vapor was increased by SPEEK/DAC membranes at high temperatures as opposed to pristine SPEEK and SPEEK/MCC membranes. [ABSTRACT FROM AUTHOR]

Water‐mediated proton conductivity in nanoporous materials is influenced by channel water ordering and the hydrophobicity/hydrophilicity of interior walls, making metal‐organic nanotubes (MONTs) useful systems for exploring these relationships due to their high crystallinity and tunable hydrophobicity. In the current study, electrochemical impedance spectroscopy is utilized to explore the proton conductivity on two metal organic nanotubes (UMONT and Cu‐LaMONT) with weak hydrophobic behavior that possess extended water networks within the 1‐D channels. Measurements performed at 95% RH and 20 °C indicate values of 1.63 × 10−4 S cm−1 for UMONT and 3.80 × 10−4 S cm−1 for Cu‐LaMONT, which is lower than values for walls with acidic, hydrophilic functional groups or nanotubular materials with strictly hydrophobic behavior. Proton conductivity decreases sharply with lower humidity, with Cu‐LaMONT being more sensitive to humidity changes. At low temperatures, UMONT outperforms LaMONT due to its well‐established hydrogen bonding network and hydrophobic interior. The anisotropic nature of proton conduction is also confirmed through pelletized powder sample analysis, emphasizing that the conductivity occurs through the water networks located within the 1‐D MONT channels. These findings emphasize the importance of understanding water–pore interactions and the resulting proton conductivity mechanisms to understand complex systems and design advanced materials. [ABSTRACT FROM AUTHOR]

An ionomer strategy is introduced to deal with two major performance‐limiting issues for the proton exchange membrane fuel cells (PEMFCs) operating under low platinum (Pt) and low humidity. Specifically, the highly hydrophilic multiple‐valence Anderson‐type polyoxometalate (POM) cluster, [MnMo6O18(OH)6]3−, is chosen to covalently graft the perfluorinated polymer, substituting for sulfonate groups as proton carriers in perfluorosulfonic acid (PFSA). The structural and electrochemical characterizations indicate that this POM cluster, with large size, charges delocalization among multiple terminal oxygen atoms, and high hygroscopicity, can prevent the ionomer adsorption, which is believed to induce dense backbone crystallization to hinder O2 permeation at Pt/PFSA interface, and lead to ionomer assemblies with large and well‐connected hydrophilic domains, which are recognized as the channels for efficient oxygen transport as well as proton conduction. Besides, the involvement of redox Mn ions in POM clusters makes the ionomer have capability to scavenge peroxides, which are known as the major chemical agents to degrade the MEA components. Consequently, fuel‐cell cathodes using the POM‐grafted ionomers exhibit significantly lower local O2 transport resistance and higher proton conductivity as compared with the PFSA‐based electrodes; and accordingly, the fuel cells exhibit much‐increased output performance at 50% relative humidity and impressive performance stability. [ABSTRACT FROM AUTHOR]

In this work, an inter-crosslinked network membrane of polyvinyl alcohol (PVA) and chitosan (CS) and SnO2 nanocparticle-incorporated nanocomposite membranes of PVA and CS (PVA/CS/SnO2) having enhanced proton conductivity have been fabricated by the solvent-casting method. SnO2 nanoparticles are synthesized using a sol–gel method, and their crystalline nature, morphology and particle size are examined using X-ray diffraction analysis, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM), and the characteristics of the membranes such as proton conductivity (PC), swelling ratio (SR), porosity, water uptake (WU), oxidative stability (OS), ion exchange capacity (IEC), and other common physiochemical characteristics were also assessed for both the bare and SnO2 nanoparticles loaded PVA/CS films. At room temperature (RT), the highest IEC rate of 0.94 mmol g−1 and proton conductivity value of 6.3 × 10−3 S cm−1 for PVA/CS/SnO2 were observed when 3 weight percent SnO2 nanoparticles were added to PVA/CS. Additionally, the PVA/CS/SnO2 compsoite membrane loaded with 3 wt% SnO2 NPs, at 80°C for 10 hours, showed outstanding OS with 12.3% degradation towards the Fenton reagent under anhydrous conditions. As this work combines the upgrading of commodity polymers, like PVA, to be employed in fuel cell devices, the nanocomposite membranes created in this work showed notable properties that may find a large place in the future fuel cell industry. [ABSTRACT FROM AUTHOR]

Covalent organic framework (COF) exhibits the great potential to promote proton conduction under low relative humidity for proton exchange membranes (PEMs). In this research, quick and stable proton conduction has been achieved since the prepared COF and polyvinylidene fluoride (PVDF) nanofibers are believed to constitute successive proton conduction channels. The PVDF-COF nanofibers membrane is prepared through the in-situ growth of COF along PVDF nanofibers. The fine compatibility can drive the stable combination of COF with the PVDF nanofibers in PVDF-COF nanofibers. Most importantly, the fibrous PVDF nanofibers accelerate proton conduction through confining the proton conduction pathways. Additionally, ionic liquids of 1-butyl-3-methylimidazolium chloride (BmimCl) and 1-butyl-3-methylimidazole hexafluorophosphate (BmimPF 6) as proton conduction carriers have been introduced to accelerate proton conduction in the prepared PVDF-COF/BmimCl/PA and PVDF-COF/BmimPF 6 /PA membranes. Phosphoric acid (PA) molecules are combined by COF and ionic liquid cations with the formation of intermolecular hydrogen bonds. As a result, the PVDF-COF/BmimPF 6 /PA membrane exhibits the proton conductivity of (1.81 ± 0.07) × 10−1 S/cm at 160 °C. The long-term proton conductivity stability is determined, deriving from the proton conductivities of 1.77×10−2 S/cm at 80 °C and 1.42×10−2 S/cm at 110 °C in the 400 h non-stop measurement. The single fuel cell equipped with the PVDF-COF/BmimPF 6 /PA membrane represents the open circuit voltage of 0.927 V and the peak power density of 178.8 mW/cm2 at 100 °C, 0.907 V and 326.5 mW/cm2 at 120 °C. [Display omitted] • Covalent organic framework is prepared. • COF and ionic liquid synergistically promote proton conduction. • Peak power densities are 178.8 mW/cm2 at 100 °C and 326.5 mW/cm2 at 120 °C. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs), which use hydrogen as fuel, present an eco-friendly alternative to internal combustion engines (ICEs) for powering low-to-heavy-duty vehicles and various devices. Despite their promise, PEMFCs must meet strict cost, performance, and durability standards to reach their full potential. A key challenge lies in optimizing the electrode, where a thin ionomer layer is responsible for proton conduction and binding catalyst particles to the electrode. Enhancing ion transport within these sub-μm thick films is critical to improving the oxygen reduction reaction (ORR) at the cathodes of PEMFCs. For the past 15 years, our research has targeted this limitation through a comprehensive "Unravel – Engineer – Design" approach. We first unraveled the behavior of ionomers, gaining deeper insights into both the average and distributed proton conduction properties within sub-μm thick films and at interfaces that mimic catalyst binder layers. Next, we engineered ionomer–substrate interfaces to gain control over interfacial makeup and boost proton conductivity, essential for PEMFC efficiency. Finally, we designed novel nature-derived or nature-inspired, fluorine-free ionomers to tackle the ion transport limitations seen in state-of-the-art ionomers under thin-film confinement. Some of these ionomers even pave the way to address cost and sustainability challenges in PEMFC materials. This feature article highlights our contributions and their importance in advancing PEMFCs and other sustainable energy conversion and storage technologies. [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]

The design and development of new and efficient catalyst binder materials are important for improving cell performance in high‐temperature proton‐exchange membrane fuel cells (HT‐PEMFCs). In this study, a series of tetrafluorophenyl phosphonic acid−based binder materials (PF‐y‐P, y=1, 0.83, and 0.67) with rigid structures and controllable degrees of phosphonation were prepared and used in HT‐PEMFCs using the ultra‐strong acid‐catalyzed Friedel−Crafts reaction and the combined Michaelis−Arbuzov reaction. The samples exhibited high stability, low water uptake, superior proton conductivity, and cell performance. In addition, the oxygen mass transport properties of the PF‐1‐P binder were investigated using high‐temperature microelectrode electrochemical testing techniques. Compared with the phosphoric acid‐doped polybenzimidazole (PBI) binder, the O2 solubility of PF‐1‐P binder material increased by 30 % (5.36×10−6 mol cm−3) and the PF‐1‐P binder material exhibited better cell stability in HT‐PEMFCs. After 10.5 h of discharge at a constant current of 0.12 A cm−2, the MEA voltage decreased by 7.1 % and 20.8 % in case of the PF‐1‐P and PBI binders, respectively. [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]

In recent years Ceria based heterostructure composites are considered as one of the highest performing solid state ionic conductors, therefore we wanted to leverage the benefits of using these materials for high temperature Proton Exchange Membrane Fuel Cells (PEMFCs). In this study a Polybenzimidazole (PBI)/Ceria carbonate CHC (Ceria based heterostructure composite) membrane was prepared by drop casting method and tested as an electrolyte for a high temperature H 2 /Air PEMFC application in anhydrous condition. Inorganic composite of ceria and alkali metal carbonates (Li 2 CO 3 , Na 2 CO 3) was prepared by solid state route to obtain Ceria carbonate CHC. X-Ray diffraction (XRD) study confirmed the formation of the heterostructure and their successful incorporation into the PBI membranes. Homogeneity of fillers inside the membrane was further verified by Energy Dispersive X-Ray Analysis (EDAX) and Scanning Electron Microscopy (SEM). 5 wt% of inorganic powder induced inside the PBI fillers reduced the phosphoric acid uptake of composite membrane (∼17% less) compared to pristine PBI membrane, which ultimately resulted into a lower swelling and dimensional change of the composite membrane. Thermal robustness of the phosphoric acid doped composite and pristine PBI membranes was investigated by thermogravimetric analysis (TGA) which showed that the prepared membranes were gone under a less than 10% reduction in weight up till 200°C, ensuring their validity of application in high temp PEM fuel cells. The added inorganic functionalities resulted in a slight increase in the proton conductivity of PA doped composite PBI membranes i.e., 42.3 mS cm−1 at 180°C while for pristine PBI membrane it is 36 mS cm−1 at same temperature. A single cell with composite PBI membranes outperformed a pristine PBI membrane resulted into a ∼120% higher peak power density i.e., 320.88 mW cm−2. The composite membrane also displayed the excellent durability and showed a less than 10−4 mV/h degradation in cell potential till 180°C. • Synthesis of Ceria-Carbonate doped mixed matrix membrane with Polybenzimidazole (PBI). • SEM images shows the homogenous dispersion of inorganic material into the membrane. • Cell voltage degradation is lower than 10−4 V/h for composite membrane. • Peak power density increases upto 120% for composite membrane compared to pure PBI membrane. [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]

In field of electrochemistry, there has been a growing interest in the potential applications of proton‐conducting metal‐organic frameworks (MOFs). Therefore, how to design and synthesize MOFs with high proton conductivity is considered crucial. In this study, two examples of nitro‐containing Cd‐based MOFs, MOF‐1 {[Cd3(TIPE)1.5(NO3)5Cl(H2O)2] ⋅ 17H2O}n and MOF‐2 {[Cd(TIPE)0.5(nip)] ⋅ 10H2O}n (TIPE=1,1,2,2‐tetrakis(4‐(1H‐imidazole‐1‐yl)phenyl)ethene, H2nip=5‐Nitroisophthalic Acid), had been successfully designed and synthesized, and their proton‐conducting properties were thoroughly investigated. Notably, both materials displayed peak proton conductivity at 98 % RH and 90 °C, exhibiting values of 9.13×10−3 and 3.00×10−3 S cm−1 for MOF‐1 and MOF‐2, respectively. The plausible proton conduction pathways and mechanisms were elucidated through structural analyses, water vapor adsorption studies, and the determination of activation energy (Ea) values. It was found that the difference in proton conductivity between MOF‐1 and MOF‐2 was mainly associated with the different water absorption rates of the samples. The uniqueness of this study was that for the first time conducted an in‐depth study of the role of nitrate in proton conduction, providing new ideas for designing materials with excellent proton conductivity. [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]

In this study, polyvinyl alcohol/Nafion nanofibrous composite membranes were produced to investigate their possible application as a polymer electrolyte membrane (PEM) in direct methanol fuel cells. Electrospinning method was used for nanofibrous membrane production, in which the mixture of polyvinyl alcohol (PVA) and Nafion solutions was directly electrospun. Produced nanofibers were subjected to physical stabilization, filler application, and sulfonating to produce composite nanofibrous membranes. PVA and Nafion polymers were used also as filler materials. The properties of resultant composite membranes were compared in terms of water swelling, weight loss in water and methanol solution, thermal stability, morphology, proton conductivity, and methanol permeability. Proton conductivity of the membranes depending on the humidity was also investigated. TGA analysis showed that the membranes had adequate thermal properties regardless of the filler material. The nanofibrous structure was shown to be preserved by scanning electron microscopy (SEM) after treatment with water and methanol solution. It was shown that PVA/Nafion nanofibers displayed proton conductivity after filling process. The use of PVA as a filler material led to higher proton conductivity at 100 RH%. It was reported that proton conductivity could only be obtained at higher relative humidity values (>80% RH). A lower methanol permeability of PVA‐filled membranes was reported. Highlights: PVA/Nafion nanofibrous membranes were produced by electrospinning.PVA and Nafion were also used as pore filling materials.PVA‐filled membranes had higher proton conductivity and lower methanol permeability.Proton conductivity could only be obtained at higher RH% values. [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]

A polymer nanocomposite based on sulfonated polyphenylene oxide with amino-functionalized mesoporous silica was designed, synthesized, and tested as a new material for proton exchange membrane (PEM preparation. Characterization of the intermediate and final products of synthesis was realized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and thermal analysis. Broadband Dielectric Spectroscopy (BDS) was used to determine dielectric properties including ionic conductivity. Thermogravimetric analysis has provided important information regarding the composition and thermal stability of the three compounds, subject to thermal degradation: 1) the amino-silica with cetyltrimethylammonium bromide (CTAB) template inside the pores (MS-NH2I), 2) the mesoporous amino-silica after removing the template (MS-NH2II) and 3) the polymer nanocomposite (sPPO-MS-NH2). The thermal decomposition of the composite samples occurs in three stages: in the first, up to 150 °C, water and organic solvents were lost; the second stage, between 200-300 °C, was due to breaking the organic functionalities (-NH2, amino and -SO3H, sulfonic acid), and the third stage, above 400 °C was due to polymer chain degradation. The final residue at 700 °C reflects the contribution of inorganic silica. The proton conductivity, for polymeric (sPPO) and composite (sPPO-MS-NH2) membranes was determined from BDS dates, both in dry and hydrated states. For dried samples, the higher values of proton conductivities were: 0.16 mS cm−1 (sPPO, 70 °C) and 0.03 mS cm−1 (sPPO-MS-NH2, 120 °C), and the higher values of proton conductivity increased for the hydrated samples with two orders of magnitude: 36.5 mS cm−1 (sPPO, 40 °C) and 22.4 mS cm−1 (sPPO-MS-NH2, 50 °C). However, the proton conductivity is still dependent on the hydration state, even for the composite membrane. [ABSTRACT FROM AUTHOR]