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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

Water in hydrophobic nanospaces shows specific dynamic properties different from bulk water. The investigation of these properties is important in various research fields, including materials science, chemistry, and biology. The elucidation of the correlation between properties of water and hydrophobic nanospaces requires nanospaces covered only with simple hydrophobic group (e.g. fluorine) without impurities such as metals. This work successfully fabricated all‐organic diamondoid porous organic salts (d‐POSs) with highly fluorinated nanospaces, wherein hydrophobic fluorine atoms are densely exposed on the void surfaces, by combining fluorine substituted triphenylmethylamine (TPMA) derivatives with tetrahedral tetrasulfonic acid. This d‐POSs with a highly fluorinated nanospace significantly improved their water stability, retaining their crystal structure even when immersed in water over one week. Moreover, this highly hydrophobic and fluorinated nanospace adsorbs 160 mL(STP)/g of water vapor at Pe/P0=0.90; this is the first hydrophobic nanospace, which water molecules can enter, in an all‐organic porous material. Furthermore, this highly fluorinated nanospace exhibits very high proton conductivity (1.34×10−2 S/cm) at 90 °C and 95 % RH. POSs with tailorable nanospaces may significantly advance the elucidation of the properties of specific "water" in pure hydrophobic environments. [ABSTRACT FROM AUTHOR]

Post Synthetic Modification (PSM) of Metal‐Organic Frameworks (MOFs) is a crucial strategy for developing new MOFs with enhanced functional properties compared to their parent one. PSM can be accomplished through various methods:1) modification of organic linkers; 2) exchange of metal ions or nodes; and 3) inclusion or exchange of solvent/guest molecules. Herein, PSM of bimetallic and monometallic MOFs containing biphenyl dinitro‐tetra‐carboxylates (NCA) are demonstrated. The tetra carboxylate NCA, produces monometallic Cd‐MOF‐1 and Cu‐MOF‐1 and bimetallic CoZn‐MOF in solvothermal reactions with the corresponding metal salts. The CoZn‐MOF undergoes post‐synthetic transmetallation with Cd(NO3)2 and Cu(NO3)2 in aqueous solution to yield Cd‐MOF‐2 and Cu‐MOF‐2, respectively. Additionally, green crystals of Cu‐MOF‐1 found to undergo a single‐crystal‐to‐single‐crystal (SCSC) transformation to blue crystals of Cu‐MOF‐3 upon dipped into water at room temperature. These MOFs demonstrate notable proton conductivities ranging from 10−3 to 10−4 S cm−1 under variable temperatures and humidity levels. Among them, Cu‐MOF‐3 achieves the highest proton conductivity of 1.36×10−3 S cm−1 at 90 °C and 98 % relative humidity, attributed to its continuous and extensive hydrogen bonding network, which provides effective proton conduction pathways within the MOF. This work highlights a convenient strategy for designing proton‐conducting MOFs via post‐synthetic modification. [ABSTRACT FROM AUTHOR]

A novel hybrid polymer electrolyte membrane (PEM) was developed for direct methanol fuel cell (DMFC) applications by incorporating sulfonated poly (ether ether ketone) (SPEEK) with a chromium‐based metal–organic framework (MOF), namely, BUT‐8(Cr). The incorporation of BUT‐8(Cr) significantly improved the dispersion of the MOF within the SPEEK matrix, leading to alterations in surface morphology and the creation of hydrophilic channels, as confirmed by SEM. Furthermore, the presence of an excess of sulfonic groups and the flexible structure of the MOF enhanced the physicochemical properties of the membrane, such as water uptake, proton conductivity and ion exchange capacity. Importantly, well‐defined rigid coordination structure of MOF effectively blocks methanol migration, resulting in a notably low methanol permeability value of 1.6 × 10−7 cm2 s−1, compared to Nafion 117 (20 × 10−7cm2s−1). For practical DMFC operation, the hybrid membrane (~0.75 wt.% MOF) exhibited a maximum power density of 88.6mWcm−2 with current density of 434.04 mAcm−2, outperforming Nafion 117 (73.4mWcm−2 and 380 mAcm−2 respectively) at same conditions. Our results suggest that the prepared SPEEK‐0.75 hybrid membrane holds a great promise as a PEM material for DMFC applications. [ABSTRACT FROM AUTHOR]

Since specifying the structure during operation tends to be challenging for intrinsically proton‐conducting polymers, it becomes increasingly essential to establish a well‐defined migration path in order to predict the proton conductivity. Zwitterion covalent organic frameworks (ziCOFs) provide a platform in crystal frameworks to investigate the proton transfer mechanism, considering their specific charged channel walls, deprotonation surface, and host–guest interactions. Here, a zwitterion nanoconfined proton‐sieves (ziNPS) with “charged casing” channel of charged pathways is proposed to demonstrate theoretically the effectiveness of proton conduction. Density functional theory and molecular dynamic simulation results show that the ziNPS with different anion groups all achieve a shorter hydrogen bond to increase the dense “hydronium‐water” domain, creating a channel of hydrogen bond networks to provide a long‐range pathway for the proton to migrate. As expected, the proton conductivity test by electrochemical impedance spectroscopy demonstrates the aforementioned concept as well. This research presents a fresh view of the ion conduction mechanism originating from localized zwitterionic units, which can apply to the fabrication of COF‐based proton conductors. [ABSTRACT FROM AUTHOR]

This study investigated the potential enhancement of proton conductivity in Nafion membranes through the incorporation of sulfo ethyl cellulose (SEC) at varying weight ratios (5 and 10 wt.%). Results indicated that increasing the weight ratio of SEC led to improvements in water absorption, activation energy, and proton conductivity within the composite membranes. Specifically, the composite membrane exhibited a significant increase in proton conductivity, reaching up to 170 mS cm−1, in contrast to the pristine Nafion membrane which recorded 40.08 mS cm−1, particularly at temperatures exceeding 120°C. At the sub‐molecular level, Fourier transfer inferred spectroscopy (FTIR) analysis of Nafion/SEC membranes unveiled cross‐linking interactions occurring between the sulfo acid groups of Nafion chains and the hydroxyls within the SEC matrix. Moreover, X‐ray diffraction (XRD) findings of the composite membranes were instrumental in identifying crystalline phases, orientation, and structural features. The results indicated variations in atomic radius and alterations in lattice parameters at the nanoscale, induced by heightened surface forces resulting from the inclusion of SEC in the Nafion matrix. This phenomenon leads to a reduction in crystallite size, accompanied by an increase in peak broadening and surface area within the composite membranes. Such changes signify a clear interaction between SEC and Nafion, as confirmed by both scanning electron microscopy and thermal gravimetry analyses. Taken together, these findings strongly indicate that the cross‐linked composite membranes utilizing SEC‐Nafion hold significant promise as proton exchange membranes. [ABSTRACT FROM AUTHOR]

Based on a novel unsaturated polyester, polybutylene fumarate (PBF), a series of sulfonated proton exchange membranes were prepared and characterized for direct methanol fuel cell application. In this work, PBF underwent sulfonation at different degrees, and the optimum degree of sulfonation (DS) was identified by assessing the hydrolytic stability. In the second step, an effective strategy to enhance the membranes' proton conductivity was adopted by the addition of the 2‐(1H‐Imidazol‐2‐yl) acetic acid (Im‐COOH) compound as a proton‐conducting agent to the sulfonated PBF (SPBF) matrix with the optimum DS. The results unveiled significant alterations in the physicochemical properties of PBF due to sulfonation, including an elevation in water uptake and the glass transition temperature (Tg), accompanied by the disappearance of the crystallinity within SPBF. In terms of electrochemical characteristics, the SPBF‐17.5 PEM demonstrated a proton conductivity of 3.36 × 10−3 S cm−1 and a methanol permeability of 1.068 × 10−7 cm2 s−1, yielding a selectivity of approximately 31,460 S s cm−3. Furthermore, the attractive interactions between SO3H and NH groups further elevated proton conductivity to 4.12 × 10−3 S cm−1, accompanied by a decrease in methanol permeability to 0.942 × 10−7 cm2 s−1, enhancing the selectivity parameter to 43,736 S s cm−3. [ABSTRACT FROM AUTHOR]

The demands of cost‐driven industrial applications can be satisfied by manufacturing composites with a low volume fraction of carbon fibres as phenolic carbon fibre‐reinforced composites and C/C composites, both with acceptable performances, for low‐ or high‐temperature applications, respectively. Polymeric composites reinforced with a low volume fraction (7.5% v/v) of carbon fibres were fabricated using laboratory‐produced phenolic resins, novolac (N) and resole (R), as matrices after different curing/post‐curing temperature profiles. By optimising the manufacturing conditions, the N‐based polymeric composites exhibited higher flexural strength, whereas the R‐based composites showed higher shear strength. C/C composites, namely N‐based and R‐based, were manufactured by pyrolysis of the previously prepared polymeric composites up to 1000 °C. The pyrolysed composites were then densified by impregnation with an appropriate resin solution, followed by curing and new pyrolysis, and particularly by employing 1 up to 4 consecutive cycles of 'impregnation–curing/pyrolysis'. Weight changes resulting from the impregnation–curing and pyrolysis stages were determined. The curing of both resins was verified by Fourier Transform Infrared Analysis. The apparent density and X‐ray diffraction data of the C/C composites were used to calculate their total percent porosities. The morphology and elemental composition of the C/C composites at their failure region (after flexural testing) were examined by Scanning Electron Microscopy/Energy‐Dispersive X‐ray Analyses. In comparison to the N‐based C/C composites, the R‐based ones exhibited: higher shear strength, lower flexural strength, higher Shore D hardness, slightly higher surface conductivity and lower volume conductivity. The optimum conditions for the manufacture of C/C composites were achieved by applying two consecutive cycles of 'pyrolysis–impregnation–pyrolysis' to the polymeric composites. © 2024 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The proton‐conducting oxides, widely employed as electrolytes in ceramic electrochemical cells, exhibit remarkable proton conductivity that facilitates efficient energy conversion processes. However, their inherent refractory nature poses a challenge in producing chemically stoichiometric and physically dense electrolytes within devices. Here a novel approach is presented, dual‐phase reaction sintering, which can overcome the inherent low sintering ability of the representative BaCeO3‐δ‒BaZrO3‐δ proton conducting oxides. This approach involves the simultaneous transformation of a two‐phase mixture (comprising fast‐sintering and slow‐sintering phases) into a complete single‐phase solid solution compound, along with the densification of the electrolyte, all accomplished within a single‐step heating cycle. During the dual‐phase reaction sintering process, the grains of the fast‐sintering phase experience rapid growth owing to their intrinsic superior sintering ability. Additionally, this growth is augmented by the Ostwald ripening behavior manifested by the smaller slow‐sintering phase. This synergistic strategy is validated using BaCe0.4Zr0.4Y0.1Yb0.1O3‐δ, and its applicability in electrochemical cells is demonstrated, resulting in a significant enhancement in performance. These findings offer insights into streamlining the preparation of refractory ion‐conducting ceramic electrolytes while maintaining their intrinsic properties for practical applications. [ABSTRACT FROM AUTHOR]

Ion conducting membranes play a crucial role in redox flow batteries, separating anolyte and catholyte while allowing proton transport to complete the circuit. However, most membranes are trapped in a trade‐off relation and show either low conductivity or high vanadium crossover. This study investigates the use of dense sulfonated para‐polybenzimidazole membranes for vanadium redox flow batteries (VRFBs), and analyzes the effects of membrane preparation process, membrane thickness and operating temperature on the VRFB performance. The results demonstrate superior performance of VRFBs utilizing fluorine‐free sulfonated para‐polybenzimidazole membranes compared to other types. Under optimal conditions, the VRFB exhibits high coulombic efficiency (>99%) and high energy efficiency (EE, 92.2% at a current density of 80 mA cm−2), and durability. The achieved EE represents one of the highest reported in the literature for VRFBs. In addition, it is shown that operation at 35 °C has benefits at high current densities (EE at 300 mA cm−2 is over 80% at 35 °C but 72% at 25 °C), while the operation at 80 mA cm−2 only shows a small temperature effect (91.8 and 92.2%, respectively). [ABSTRACT FROM AUTHOR]

Ionomers are important to electrode function in energy conversion devices, such as fuel cells and electrolyzers, as the catalyst‐binding nanometer‐thick films under confinement, which compromises mass transport of species. Mitigating confinement effects is necessary for improved performance of polymer electrolyte fuel cells. Studies on perfluorosulfonic acid (PFSA) ionomers provided insights into origins of transport resistances, but limited improvements by current strategies necessitate a need for alternative chemistries to enhance film function. This work investigates new ionomers based on sidechain modifications of PFSA to tune local acidity and structure. Their application‐relevant properties (hydration, thermal‐transition) and nanomorphology are systematically characterized using environmental ellipsometry and grazing‐incidence X‐ray scattering, respectively, to develop chemistry‐structure‐property relationships in thin‐film motif (≤100 nm). Introducing acid sites to sidechains improves hydration and nano‐phase‐separation but reduce chain mobility. Replacing the hydrophilic end‐groups with hydrophobic perfluoro‐groups enhances mobility but disrupts phase‐separation. Although modifying sidechain functional groups alters ionomer‐substrate interactions (Pt/C), chemistry has greater influence on structure‐properties. Proton conductivity correlates with hydration, regardless of chemistry. This work improves the fundamental understanding of chemistry‐function relationships of ionomers by providing a novel means to independently control their side‐chain vs. end‐group and observe resulting effects on interfacial properties to modulate electrode function in electrochemical technologies. [ABSTRACT FROM AUTHOR]

In this study, we synthesized and characterized a new Co(II)‐based coordination polymer, denoted as {[Co(HL)(dpa)]·H2O}n (1), derived from the H3L ligand and dpa co‐ligand. Single crystal X‐ray diffraction revealed that 1 forms a two‐dimensional (2D) layer and a three‐dimensional (3D) supramolecular structure via hydrogen bonding interactions. Presence of carboxylic acid groups in 1 was confirmed by X‐ray crystallography, prompting investigation into its proton transport properties. Additionally, electrostatic potential surface and nucleophilic index analyses were conducted to simulate potential proton transfer pathways. Furthermore, we prepared nine modified encapsulated materials using 1 as the base material (SDA@1, APH@1, APY@1, TA@1, BA@1, DIC@1, IDZ@1, SCA@1, and TYD@1), and tested their proton conductivity and activation energy compared to pure Nafion membrane and 1, analyzing the influence of different small molecule structures on proton conductivity. Comparative analysis revealed that only SDA@1 exhibited enhanced proton conductivity and reduced activation energy at 303 K, with an improvement rate of 220.8%. We hope that the methods presented herein can provide valuable insights for the design and development of high‐performance proton‐conducting materials, as well as for the exploration of proton conduction mechanisms. [ABSTRACT FROM AUTHOR]

A novel polybenzimidazole (PBI)‐based trilayer membrane assembly is developed for application in vanadium redox flow battery (VRFB). The membrane comprises a 1 µm thin cross‐linked poly[2,2′‐(p‐oxydiphenylene)−5,5′‐bibenzimidazole] (OPBI) sandwiched between two 20 µm thick porous OPBI membranes (p‐OPBI) without further lamination steps. The trilayer membrane demonstrates exceptional properties, such as high conductivity and low area‐specific resistance (ASR) of 51 mS cm−1 and 81 mΩ cm2, respectively. Contact with vanadium electrolyte increases the ASR of trilayer membrane only to 158 mΩ cm2, while that of Nafion is 193 mΩ cm2. VO2+ permeability is 2.73 × 10−9 cm2 min−1, about 150 times lower than that of Nafion NR212. In addition, the membrane has high mechanical strength and high chemical stability against VO2+. In VRFB, the combination of low resistance and low vanadium permeability results in excellent performance, revealing high Coulombic efficiency (>99%), high energy efficiency (EE; 90.8% at current density of 80 mA cm−2), and long‐term durability. The EE is one of the best reported to date. [ABSTRACT FROM AUTHOR]

For protonic ceramic fuel cells, it is key to develop material with high intrinsic activity for oxygen activation and bulk proton conductivity enabling water formation at entire electrode surface. However, a higher water content which benefitting for the increasing proton conductivity will not only dilute the oxygen in the gas, but also suppress the O2 adsorption on the electrode surface. Herein, a new electrode design concept is proposed, that may overcome this dilemma. By introducing a second phase with high‐hydrating capability into a conventional cobalt‐free perovskite to form a unique nanocomposite electrode, high proton conductivity/concentration can be reached at low water content in atmosphere. In addition, the hydronation creates additional fast proton transport channel along the two‐phase interface. As a result, high protonic conductivity is reached, leading to a new breakthrough in performance for proton ceramic fuel cells and electrolysis cells devices among available air electrodes. [ABSTRACT FROM AUTHOR]

The design and synthesis of proton exchange membranes (PEMs) with controllable microstructure and sulfonation degree play a crucial role in enhancing their performance and expanding their application. In this study, the disulfonic acid monomer is designed and prepared to synthesize the comb‐like disulfonic PEMs with controllable ion exchange capacity. The results show that the side chain structure and more concentrated sulfonic acid groups facilitate the aggregation of sulfonic acid groups in the polymer, improve the microphase separation morphology of PEMs, and increase the ionic conductivity. The proton conductivity of the DS‐PXIDI‐60 membrane is approximately 300 mS cm−1. The PEMs with controllable microstructure are prepared by introducing comonomers, including 9,9‐dimethylxanthrene, biphenyl, and p‐terphenyl, with different reactivity, spatial structure, and solubility. Biphenyl is copolymerized to form a copolymer with an alternating structure, and 9, 9‐dimethylxanthrene is copolymerized to form a random copolymer. In addition, it is worth noting that p‐terphenyl is copolymerized to form a microblock structure of the copolymer, with more excellent comprehensive properties. DS‐PXITp‐60 exhibits better performance than Nafion 212 in redox-flow batteries and fuel cells. Therefore, such molecular design and synthesis strategies provide a reference guide for the development of high‐performance PEMs. [ABSTRACT FROM AUTHOR]

Alkaline earth (AE) metal complexes have garnered significant interest in various functional fields due to their nontoxicity, low density, and low cost. However, there is a lack of systematic investigation into the structural characteristics and physical properties of AE‐metal‐organic frameworks (MOFs). In this research, we synthesized isostructural MOFs consisting of AE4(μ4‐Cl) clusters bridged by benzo‐(1,2;3,4;5,6)‐tris(thiophene‐2′‐carboxylic acid) (BTTC3−) ligands. The resulting structure forms a truncated octahedral cage denoted as [AE4(m4‐Cl)]6(BTTC)8, which further linked to a porous three‐dimensional framework. Among the investigated AE ions (Ca, Sr, and Ba), the Ca4‐MOF demonstrated good chemical stability in water compared to Sr4‐MOF and Ba4‐MOF. The N2 adsorption and solid‐state UV‐vis‐NIR absorption behaviors were evaluated for all AE4‐MOFs, showing similar trends among the different metal ions. Additionally, the proton conduction study revealed that the Ca4‐MOF exhibited ultra‐high proton conductivity, reaching 3.52×10−2 S cm−1 at 343 K and 98 % RH. Notably, the introduction of LiCl via guest exchange resulted in an improved proton conduction of up to 6.36×10−2 S cm−1 under similar conditions in the modified LiCl@Ca4‐MOF. The findings shed light on the regulation of physical properties and proton conductivity of AE‐MOFs, providing valuable insights for their potential applications in various fields. [ABSTRACT FROM AUTHOR]

In this study, the preparation, characterization, and fuel cell performance tests of high‐performance and low‐cost zirconium phosphate (ZrP)‐additive sulfonated polyethersulfone (sPES) membranes, which may serve as a substitute for the commercial membrane used in proton exchange membrane fuel cell (PEMFC), were carried out. ZrP‐additive sPES membranes were prepared by solution casting method with different weight ratios (2.5%, 5%, and 9%). Fourier transform infrared (FTIR), water uptake capacity (WUc), dynamic mechanical analysis, ion exchange capacity (IEx), degree of hydration, impedance analysis, and oxidative stability were used to characterize the created membranes. Ultimately, single‐cell performance experiments were used to evaluate the membranes' performance in real fuel cell environments. ZrP additive improved the WUc, mechanical properties, IEx, and proton conductivity properties of the membrane. WUc of the membranes enhanced by approximately 94% at 80°C, while the proton conductivity augment by approximately 47% with 9% ZrP by weight. 0.97 meq g−1 IEx was obtained for the sPES, whereas it was obtained as 1.41 meq g−1 for sPES‐9ZrP. Oxidative stability experiments for 120‐h determined that all synthesized membranes had a stable structure, and their weight losses varied between 68% and 85%. The sPES‐9ZrP exhibited very high values at 0.6 V, resulting in a power density of 680 mW cm−2 and a current density of 1100 mA cm−2. The results obtained are quite promising, and sPES and ZrP in composite membrane structures have high synergy. [ABSTRACT FROM AUTHOR]

Anisotropic gels developed from polymer networks accommodating lyotropic liquid crystals are promising electrolytes but electrochemically inert polymers prevent ions from being conducted efficiently. In this work, we synthesized protic ionic liquid polymer in lyotropic ionic liquid crystal to improve proton conduction across the polymer skeleton in anisotropic gels. In situ polymerization of 1‐vinylimidazolium hydrogen sulfate ionic liquid dissolved in aqueous 1‐tetradecyl‐3‐methylimidazolium hydrogen sulfate lyotropic liquid crystal gave chemical liquid crystal gels exhibiting both dynamic order and mechanical strength. The protic ionic liquid polymer bridged the hydrogen bond chains between neighboring ionic lyotropic liquid crystal domains to give a proton conductivity of 117 mS cm−1 at 25°C. Macroscopic alignment of the liquid crystal gel achieved by mechanical shearing promoted proton conductivity to 137 mS cm−1. The macroscopically aligned liquid crystal gel acted stably in a fuel cell device, delivering a peak power density 2.95 times higher than the unaligned one. Gelation of lyotropic ionic liquid crystals with protic ionic liquid polymer provides an effective strategy to develop anisotropic gel electrolytes for electrochemical devices. [ABSTRACT FROM AUTHOR]

A polyaryleneether has been synthesized from bis‐(4‐cholorophenyl)di‐acetal (DPDA) monomer with bisphenol A and allyl bisphenol‐A. The copolymer was then functionalized with 2‐acrylamide‐2‐methyl propane sulfonic acid through radical grafting (SPAE/DPDA). The successfully synthesized SPAE/DPDA polymer was validated by using FTIR and NMR. Secondly, a composite nanostructure of MoS2/GNS nanosheet has been prepared and characterized using PXRD, FE‐SEM, and HR‐TEM. The composite membrane casted with SPAE/DPDA and varying weight percentage of 1%, 2%, 3%, 5%, 7%, and 10% MoS2/GNS nanosheet, has been characterized for ion exchange capacity (IEC), water stability (WU), swelling properties (SR), oxidative stability, and proton conductivity (PC).The MoS2/GNS dispersed SPAE/DPDA polymer nanocomposites membrane showed a chemical degradation of 22.56% and proton conductivity (PC) of 2.5 × 10−2 S/cm at 110°C. The results show that these membranes have high proton conductivity and can be used in proton exchange membrane fuel cells (HT‐PEMFCs). [ABSTRACT FROM AUTHOR]

How to optimize and regulate the distribution of phosphoric acid in matrix, and pursuing the improved electrochemical performance and service lifetime of high temperature proton exchange membrane (HT‐PEMs) fuel cell are significant challenges. Herein, bifunctional poly (p‐terphenyl‐co‐isatin piperidinium) copolymer with tethered phosphonic acid (t‐PA) and intrinsic tertiary amine base groups are firstly prepared and investigated as HT‐PEMs. The distinctive architecture of the copolymer provides a well‐designed platform for rapid proton transport. Protons not only transports through the hydrogen bond network formed by the adsorbed free phosphoric acid (f‐PA) anchored by the tertiary amine base groups, but also rely upon the proton channel constructed by the ionic cluster formed by the t‐PA aggregation. Thorough the design of the structure, the bifunctional copolymers with lower PA uptake level (<100%) display prominent proton conductivities and peak power densities (99 mS cm−1, 812 mW cm−2 at 160 °C), along with lower PA leaching and higher voltage stability, which is a top leading result in disclosed literature. The results demonstrate that the design of intermolecular acid–base‐pairs can improve the proton conductivity without sacrificing the intrinsic chemical stability or mechanical property of the thin membrane, realizing win‐win demands between the mechanical robustness and electrochemical properties of HT‐PEMs. [ABSTRACT FROM AUTHOR]

In this paper, sulfonic acid functionalized benzothiazole ionic liquid ([(CH2)3SO3HBth] [H2PO4]) and graphene oxide were combined together through the cation‐π. The sulfonated poly (ether ether ketone) was doped with ionic liquid‐modified GO (IL‐GO) to prepare the SPEEK/IL‐GO composite membrane through the solution casting method. The SO3H and benzothiazole rings act as both proton acceptors and proton donors during proton transport and can replace the role of water in medium‐ and high‐temperature environments, increasing the proton transport sites to a certain extent and increasing the proton conductivity of the SPEEK/IL‐GO composite membrane. The proton conductivity of the SPEEK/IL‐GO‐2 composite membrane achieved an 18.02 mS/cm at 120°C, which is 2.43 times higher than that of the pristine SPEEK membrane. This paper provided a method for increasing proton conductivity and limiting IL loss of the SPEEK membrane. Highlights: [(CH2)3SO3HBth][H2PO4] and graphene oxide were combined through cation‐π.The benzothiazole ring and SO3H form acid–base pairs.The proton conductivity of SPEEK/IL‐GO‐2 membrane achieved 18.02 mS/cm. [ABSTRACT FROM AUTHOR]

Nafion has been dominating the proton exchange membrane (PEM) market because of its adequacy for the proton exchange operation. However, because of its high cost, low performance at low relative humidity, and finally environmental unfriendliness, researchers have been developing and working on Nafion alternatives. In this review, we assess how biopolymers present an opportunity as an eco‐friendly material able to replace the conventional Nafion membrane in proton exchange membrane fuel cells (PEMFC). Chitosan and cellulose were the most studied in literature owing to their abundance in nature, low cost, and high affinity for water, which are sought‐after properties for PEM. In addition to that, their ease of modification through their hydroxyl or amine groups represents an opportunity to further enhance their characteristics and thus meet the criteria of diverse applications. The use of biopolymers as an adequate PEM is facing many challenges. Having a practical proton conductivity and securing the physicochemical stability of the biopolymers in fuel cell operating conditions are two of the most important challenges to overcome. Promising strategies to simultaneously address these challenges such as crosslinking, making interpenetrated networks, and making blends and composites are reported. [ABSTRACT FROM AUTHOR]

Fast proton conduction plays an essential role in ion conductive membranes (ICMs) for energy conversion and storage technologies, but the demand for low reactive species permeation always limits further enhancement in proton transport rate. Herein, an ICM incorporating ZSM‐5 zeolite with optimized physicochemical property of pore channels was developed to achieve highly conductive ion transport via regulating the silicon‐aluminum atomic (Si/Al) ratio of ZSM‐5. Benefiting from the regulation of pore channels of zeolites, the proton conductivity of the pristine membrane was remarkably improved to 1.7‐fold. As expected, the optimized membrane exhibited outstanding voltage efficiency (VE) of 85.7% and energy efficiency (EE) of 85.1% at 120 mA/cm2, which is considerably better than pure polymer membrane (VE of 80.5% and EE of 79.4%) and commercial Nafion 212 (VE of 81.3% and EE of 77.4%) membrane, respectively. [ABSTRACT FROM AUTHOR]

Achieving rapid ion transport through nanochannels is essential for both biological and artificial membrane systems. Covalent organic frameworks (COFs) with well-defined nanostructures hold great promise for addressing the above challenge. However, due to the limited processability and inadequate interlamellar interaction of COF materials, it is extremely difficult to integrate them to prepare high-performance proton conductors. Herein, inspired by the ingenious bio-adhesion strategy in nature, ultrafast proton conduction is achieved by taking advantage of COF membranes where TP-COF nanosheets are linked by subnanometer nanowires/lignocellulosic nanofibrils composites (SNWs/LCNFs) through electrostatic and π-π interactions to form an ordered and robust structure. Notably, the synthesized SNWs exhibited impressive proton conductivity and adhesion capacity due to their inbuilt phosphotungstic acid (HPW) molecules and multidimensional interactions. Therefore, attributed to the synergistic contribution of TP-COFs and SNWs, the composite membrane achieves ultrahigh proton conductivity (0.395 S cm-1 at 80 °C and 100% RH), superior mechanical property (109.8 MPa), exceptional fuel cell performance (71.6 mW cm-2), and superior operational stability (OCV decay rate is about 1.5 mV h-1), demonstrating outstanding competitiveness. More importantly, the proposed design concept has the potential to be applied in membranes for various electrochemical devices and molecular separations. [ABSTRACT FROM AUTHOR]

Reversible protonic ceramic electrochemical cells (R-PCECs) are emerging as highly efficient energy conversion devices, operating below 650 °C. The primary challenge in advancing R-PCECs lies in developing efficient and stable proton-conducting electrolytes capable of withstanding the chemical instability caused by common contaminants like CO2 and H2O. Herein, a novel high-entropy perovskite oxide (HEPO) material is introduced, incorporating six equimolar B-site cations (BaHf1/6Sn1/6Zr1/6Ce1/6Y1/6 Yb1/6O3-δ, BHSZCYYb). The total conductivity of BHSZCYYb outperforms that of the examined HEPO electrolytes and other reported HEPO variants. Additionally, superior chemical stability of BHSZCYYb is observed when exposed to CO2. Utilizing the microwave-assisted sintering method, an R-PCEC with BHSZCYYb electrolyte is successfully fabricated. This cell exhibits a maximum power density of 1.151 W cm-2 (650 °C) in fuel cell mode and a current density of 2.326 A cm-2 at 1.3 V (650 °C) in electrolysis cell mode. These results represent the highest-reported values for R-PCECs employing HEPO electrolytes to date and provide valuable insights into the development and advancement of HEPOs, holding great promise for achieving high-performance R-PCECs. [ABSTRACT FROM AUTHOR]

Ladder systems situated in the dimensional crossover region have attracted much attention because their electronic states and physical properties depend strongly on the electronic correlations among the constituent legs. Generally, two‐/three‐legged transition metal‐oxide ladder compounds are studied as representative ladder systems, but two‐/three‐dimensional (2D/3D) extensions based on such ladder systems with a few numbers of legs are difficult because of the extreme synthesis conditions. Here, for the first time, we report the successful creation of a 3D extended two‐legged ladder compound, [Pt(en)(dpye)I]2(NO3)4 ⋅ 2H2O (en=ethylenediamine; dpye=1,2‐Di(4‐pyridyl)ethane), which is obtained by simple oxidative polymerization of a small Pt macrocyclic complex using elemental I2. The unique 3D extended lattice consists of 1D mixed‐valence halogen‐bridged metal chains (⋅⋅⋅Pt−I−Pt−I⋅⋅⋅) and helically arranged macrocyclic units as the constituent legs and rungs, as confirmed by single‐crystal X‐ray diffraction. Diffuse X‐ray scattering analyses and optical measurements revealed that the out‐of‐phase mixed‐valence Pt2+/Pt4+ arrangement arises from the weak interchain correlation among adjacent legs. In addition, this compound shows an increase in proton conductivity by a factor of up to 1000, depending on humidity. [ABSTRACT FROM AUTHOR]

As a new type of proton conductor, metal–organic frameworks (MOFs) have attracted much attention because of their superior properties over conventional materials, such as the modifiability of framework, reversibility of coordination bond, high specific surface area, and porosity. It is predicted that the proton conductivities of MOFs can be improved by hole expansion and ionic liquid introduction. In this work, HKUST‐1 and LP‐HKUST‐1 were prepared, which were filled with different proportions of N‐methylimidazole triflate (MIM‐CF3SO3) to prepare composite materials MIM‐CF3SO3@HKUST‐1‐100% and MIM‐CF3SO3@LP‐HKUST‐1‐x (x = 25%, 50%, 75% and 100%). A total of seven kinds of materials were synthesized. The proton conductivities of all the materials at 75% RH were tested from 303 to 353 K. In this environment, MIM‐CF3SO3@LP‐HKUST‐1‐100% shows excellent proton conductivity (σ = 0.341 S·cm−1 at 353 K, 75% relatively humidity [RH]), being 7060 times that of HKUST‐1, and reaches the peak value of MOF family in recent years. Then, the conductivities of parts of the materials were tested in extreme environments, such as in high‐humidity environment (303–353 K, 100% RH), high‐temperature environment (373–423 K, N2 atmosphere), and low‐temperature environment (253–283 K, 75% RH). The results show that under all conditions above, the proton conductivity of MIM‐CF3SO3@LP‐HKUST‐1‐100% is the best, up to 0.341 S·cm−1 at 353 K and 75% RH, 0.179 S·cm−1 at 353 K and 100% RH, 1.31 × 10−3 S·cm−1 at 283 K and 75% RH, and 2.31 × 10−4 S·cm−1 at 423 K and N2 atmosphere, indicating that proton conductivity of HKUST‐1 is improved by hole expansion and ionic liquid introduction. Finally, the stability test showed that MIM‐CF3SO3@LP‐HKUST‐1‐100% was stable in all environments above. Moreover, the conductive mechanism of HKUST‐1 before and after introduction of ionic liquids was also discussed, providing a theoretical basis for the enhancement of proton conductivities of MOFs using ionic liquid introduction and hole expansion. [ABSTRACT FROM AUTHOR]

In this study, sulfonated poly(arylene ether sulfone) (SPAES) and sulfonated poly(arylene ether ketone) (SPAEK) were randomly synthesized, employing a presulfonation process. This presulfonation process resulted in a more controlled and reproducible sulfonation level. The respective polymers were prepared using 2,2‐Bis(4‐hydroxyphenyl) propane at 50% molar ratio, which also provided some membrane elasticity. The resulting polymers, each had 25% of the block containing the sulfonic domains (SPAES A 25 and SPAEK A 25). Better conductive membranes were achieved for the random sulfone polymers than for the random ketone polymers, with values, respectively, of 0.24 and 0.07 S cm−1 at 80°C. The lower proton conductivity from the ketone‐based polymer was compensated with very low methanol permeability (0.25 × 10−6 cm2 s−1) and outstanding oxidative stability. The selectivity of both polymer membranes exceeded the reported values for the state‐of‐the‐art Nafion® 117 and other commercially available options. Both polymer membranes, with their unique combination of ionic domains, elastomeric blocks, and resulting morphology, could be viable candidates for fuel cell applications. [ABSTRACT FROM AUTHOR]

Biological macromolecules exhibit emergent functions through hierarchical self‐assembly, a concept that is extended to design artificial supramolecular assemblies. Here, the first example of breaking the common parallel arrangement of capsule‐shaped zirconium coordination cages is reported by constructing the hierarchical porous framework ZrR‐1. ZrR‐1 adopts a quaternary structure resembling protein and contains 12‐connected chloride clusters, representing the highest connectivity for zirconium‐based cages reported thus far. Compared to the parallel framework ZrR‐2, ZrR‐1 demonstrated enhanced stability in acidic aqueous solutions and a tenfold increase in BET surface area (879 m2 g−1). ZrR‐1 also exhibits excellent proton conductivity, reaching 1.31 × 10−2 S·cm−1 at 353 K and 98% relative humidity, with a low activation energy of 0.143 eV. This finding provides insights into controlling the hierarchical self‐assembly of metal–organic cages to discover superstructures with emergent properties. [ABSTRACT FROM AUTHOR]

High‐temperature proton‐exchange membrane fuel cells (HT‐PEMFCs) fabricated with phosphoric acid (PA)‐doped polybenzimidazole (PBI) show apparent technical advantages. In practical automotive applications, achieving cold start‐up capability is crucial. In this work, a kind of branched block proton exchange membrane (PEM) based on PBI with a low content of porphyrin ring (<1 mol.%) is reported as a branched monomer. Self‐assembly into high‐density helical nanochannels under the synergistic effect of phase separation and porphyrin π−π stacking, thus the PEM can maintain a high level of PA doping. Specifically, the PA/1.8TCPP‐BrPy‐OPBI membrane shows a proton conductivity of 0.169 and 0.071 S cm−1, as well as an H2‐O2 fuel cell peak power density of 1077 and 357 mW cm−2 at 180 and 80 °C without humidification and backpressure, respectively. The membrane electrode assembly (MEA) can exhibit good fuel cell stability, with a voltage decay rate of only 7.0 µV h−1 at 80 °C. Furthermore, it maintains a peak power density of 93% even after 150 start‐up/shut‐down cycles at 25 °C. This work expands the operating temperature range of conventional PBI membranes between 25 and 200 °C and thus provides a novel strategy for high‐performance PBI‐based HT‐PEMFCs. [ABSTRACT FROM AUTHOR]

Nanoparticles and nanofibers are widely used as components of polymer electrolytes for membranes in fuel cells, and many surface modification methods are reported. However, some fabrication techniques are complicated, and it is necessary to develop a simplified and precise control method. Herein, a facile fabrication method is reported for core–shell nanoparticles hierarchically coated with polymeric ionic liquids (PIL) and hydrophobic polymers as a material for polymer electrolytes. A hierarchical polymer layer on the surface of the SiO2 nanoparticles is easily constructed by repeating the facile polymer‐coating technique based on precipitation polymerization several times. The highest proton conductivity of the core–shell nanoparticles is 1.3 × 10−2 S cm−1 at 80 °C and 95% relative humidity. Although the hydrophobic polymers coated as a protective layer reduce the proton conductivity, the formation of the PIL enhances the proton conductivity in various temperature and humidity environments. Therefore, the proposed method enables the facile fabrication of polymer layers with multiple functions, such as a proton‐conductive PIL layer and hydrophobic polymer layers as protective layers on the surface of the nanoparticles. Furthermore, they are expected to be applied to energy supply and gas separation, including polyelectrolytes, for the realization of a sustainable society. [ABSTRACT FROM AUTHOR]

The "visible" proton‐conducting pathway offers a distinct advantage for researching the mechanism of proton conducting materials at the molecular level and developing new materials. To achieve this, three crystalline materials are constructed via acid–base chemistry based on phosphomolybdic acid and diversfied guanidine, namely, (CN3H6)6(PMo12O40)2·H2O (GH–PMo12), (CN4H7)3(PMo12O40)·H2O (AGH–PMo12), and (CN5H8)3(PMo12O40)·3.5H2O (DAGH–PMo12). Proton conductivity of GH–PMo12 in the [001] direction reaches up to 0.19 S cm−1 at 85 °C and 98% RH, as elucidated by impedance studies of single crystals. The clear proton transport path is proposed through the analysis of single crystal structure. Moreover, impedance studies of powder crystals reveal that the proton conductivity of GH–PMo12 is higher than that of the other two compounds. The underlying reasons for this result are clarified through the analysis of the pKa, proton density, and spatial structure. Additionally, GH–PMo12 is fabricated into composite membrane with a peak proton conductivity of 5.31 × 10−2 S cm−1, which exhibits promising potential for real‐world applications. [ABSTRACT FROM AUTHOR]

Excessive swelling is one important factor that leads to high fuel permeability and limited operating concentration of methanol for proton exchange membranes. Herein, a collaborative strategy of main‐chain and molecular‐network engineering is applied to lower swelling ratio and improve methanol resistance for highly sulfonated polyimide. Two m‐phenylenediamine monomers (4‐(2,3,5,6‐tetrafluoro‐4‐vinylphenoxy)benzene‐1,3‐diamine and 4,6‐bis(2,3,5,6‐tetrafluoro‐4‐vinylphenoxy)benzene‐1,3‐diamine) with tetrafluorostyrol groups are designed and synthesized. Two series of cross‐linked sulfonated polyimides (CSPI‐Ts, CSPI‐Bs) are prepared from the two diamines, 4,4′‐diaminostilbene‐2,2′‐disulfonic acid and 1,4,5,8‐naphthalenetetracarboxylicdianhydride. The rigid main‐chain structure is cornerstone for wet CSPI‐Ts and CSPI‐Bs remaining stable at elevated temperatures. The introduction of hydrophobic cross‐linked network further improves their dimensional stability and methanol resistance. CSPI‐Ts and CSPI‐Bs show obviously improved performances containing high proton conductivity (121 ± 0.27–158 ± 0.35 S cm−1), low swelling ratio (9.6 ± 0.40%–16.1 ± 0.01%) and methanol permeability (4.14–7.69 × 10−7 cm2 s−1) at 80 °C. The direct methanol fuel cell (DMFC) is assembled from CSPI‐T‐10 with balanced properties, and it exhibits high maximum power density (PDmax) of 82.3 and 72.6 mW cm−2 in 2 and 10 m methanol solution, respectively. The ratio of PDmax in 10 m methanol solution to the value in 2 m methanol solution is as high as 88%. The CSPI‐T‐10 is promising proton exchange membrane candidate for DMFC application. [ABSTRACT FROM AUTHOR]

A myriad of metal ions and organic linkers can be used to produce metal–organic frameworks (MOFs) with varied functionalities, porosities, and dimensionalities. Such diversity has garnered significant research interest, particularly in leveraging MOFs as proton conductors for fuel cells. One effective approach involves introducing guest molecules into MOF pores. These molecules serve either as proton carriers or as proton‐conducting media through potential hydrogen bonding networks. This review offers an organized overview of key methodologies historically employed to achieve superprotonic conductivity in MOFs. The article systematically categorizes these tactics into three primary groups: guest molecule encapsulation, modulation at metal‐coordination sites, and ligand functionalization. We succinctly discuss the roles of proton carriers, conducting media, and the overall MOF framework, emphasizing the significance of each strategy's application. In conclusion, we provide insights into the future development of MOFs as proton conductors, rooted in the categorization and conceptual understanding of these strategies. [ABSTRACT FROM AUTHOR]