Enhanced Proton Conductivity Research Articles

Synergistic proton conduction via Ca-vacancy coupled with Li+-bridge in Ca5(PO4)3OH

Proton conductivity plays a crucial role in the advancement of materials for proton ceramic fuel cells (PCFCs) and a variety of electrochemical devices. Traditional approaches to enhancing proton conductivity in perovskites have largely relied on doping strategies to induce structural oxygen vacancies. However, these methods have yet to overcome the challenges associated with achieving desired proton conductivity. Here, we introduce an approach wherein intermediate Li+ ions act as a bridge linked to Ca vacancies, fostering a mechanism for accelerated proton transport. Utilizing protonated Ca5(PO4)3OH-H(Li) as an electrolyte, we achieve a proton conductivity of 0.1 S cm−1 and a fuel cell performance of 661 mW cm−2 at an operational temperature of 550 °C for realizing low temperature PCFCs. This proton transport synergy overcomes traditional doping limitations, enabling the advancement of proton-conducting electrolytes and enhancing the efficiency of proton conducting electrolyte fuel cells, with implications in energy conversion and storage technologies.

Investigating the Role of Aniline Structure in Improving Proton Exchange Membranes for High Conductivity.

Polybenzothiazole exhibits high proton conductivity; however, its rigid backbone limits its applicability, necessitating processes such as modification or doping. The aniline structure can participate in various reactions, including nucleophilic or electrophilic substitution reactions, salt formation, and acylation reactions. In this experiment, an aniline structure is integrated into the main chain of sulfonated polybenzothiazole to investigate the potential of aniline for enhancing proton exchange membranes. The incorporation of the aniline structure is confirmed through infrared and nuclear magnetic resonance analyses. A comparison of different proportions of aniline revealed that 12.5% aniline increased the tensile modulus to 274.40MPa and the elongation at break to 6.26%. Furthermore, the water absorption rate reached 65.73%, while the expansion rate remained at 25%. The aniline structure exhibits inherent basicity and utilizes phosphoric acid adsorption to enhance proton conductivity. After aniline adsorbs phosphoric acid, the proton conductivity peaks at 0.157 Scm-1. Additionally, the introduction of amino groups provides further modification potential to the main chain of polybenzothiazole.

A high power metal-supported protonic ceramic fuel cell using increased proton conductivity in the cathode functional layer of La1−xSrxScO3 (LSSc, x = 0.1–0.25)

Metal-supported protonic ceramic fuel cells (PCFCs) with LSSc layers achieve enhanced proton conductivity and improved power density.

Uncoordinated Carboxyl Groups as Proton Sources in Polyoxometalate-Based Metal-Organic Frameworks Enhance Proton Conduction.

To select appropriate organic ligands is an effective strategy to enhance the proton conductivities of polyoxometalate-based metal-organic frameworks (POMOFs). Two new Dawson-type POMOFs, named CUST-961 and CUST-962, have been designed and synthesized via combining Htzbc selected by hard and soft acid and base theory and density functional theory calculation, transition metal ions, alkali metal ions (Na+ and K+), and Dawson-type polyoxometalates ([P2W18]6-) under the hydrothermal method. Their stabilities under different temperatures and relative humidities (RHs) have been investigated through powder X-ray diffraction and thermogravimetric analysis. Both CUST-961 and CUST-962 exhibited excellent aqueous and thermal stabilities. The alternating current (AC) impedance spectrum tests revealed that the proton conductivity of CUST-961 could reach 1.4 × 10-4 S cm-1 at 95 °C and 98% RH, which is about 3 times that of CUST-962. The different proton conductivities between the two compounds are due to the fact that CUST-961 possesses more uncoordinated carboxylic acid groups, as confirmed by attenuated total reflection infrared spectroscopy and 1H solid-state nuclear magnetic resonance spectroscopy, which can not only act as the proton source but also establish a richer hydrogen bonding network to enhance proton conduction. This work provides a new strategy and insight for the design and preparation of polyoxometalate-based proton conductive materials.

A 3D Zn-MOF for Luminescent Sensing of p-Nitrophenol and L-Lysine, and Enhanced Proton Conduction Properties

A 3D Zn-MOF for Luminescent Sensing of p-Nitrophenol and L-Lysine, and Enhanced Proton Conduction Properties

Unveiling exceptional conduction mechanism and high proton conductivity in amorphous electrolyte for advanced ceramic fuel cells

The requirement of high ion conductive material working at low temperatures is highly demanding in fuel cells. This study explains a groundbreaking advancement in ceramic fuel cells by exploring the potential of amorphous Sm0.3Al0.7-oxide and the proton conduction mechanism of amorphous oxides. Opposite to conventional crystalline electrolytes, amorphous electrolytes showed superior ion conduction. To study the detailed mechanism of ion conduction, amorphous Sm0.3Al0.7-oxide was selected which exhibited an exceptional proton conductivity of 0.17 S/cm and a power density of 1100 mW/cm2 at 550 °C, significantly surpassing traditional electrolyte materials. Using advance characterization techniques, a new approach has been proposed to provide the reasons for the high conductivity of amorphous materials, which entails a complete mechanism that describes how disordered structure and disoriented grain boundaries facilitate efficient proton conduction by reducing energy barriers and enhancing ionic mobility. Also, it has been described how the high enthalpy and the high energy state of amorphous materials are suitable for enhancing proton conduction. This study aims to clarify why amorphous materials are promising candidates for future fuel cell applications, facilitating significant advancements in SOFC and PCFC technologies and paving the way for more efficient and sustainable energy solutions.

A Novel Strategy to Construct Metal–Organic Frameworks‐Based Memristor with Enhanced Proton Conduction

The limited conductivity of metal‐organic frameworks (MOFs) poses a significant challenge to their application in the domain of memristors. The proton conduction capabilities of MOFs can be improved through the incorporation of guest molecules. Herein, hydrogen protons are introduced into MIL‐53 (Al) via acid leaching, which not only enhances the proton conductivity of MIL‐53 (Al) but also contributes to its superior resistance switching behavior. The results indicate that untreated MIL‐53 (Al) exhibits negligible resistance switching behavior; however, following hydrochloric acid leaching, it demonstrates excellent retention (103 cycles), longtime durability (103 s), and a favorable ON/OFF ratio (≈25) under bias conditions. Furthermore, under suitable pulse stimulation, the MIL‐53 (Al)‐based memristor successfully emulates biological synaptic behaviors, including excitatory postsynaptic current and paired pulse facilitation. This research presents a novel approach for enhancing the resistive switching performance of MOF‐based memristors.

Semi-interpenetrating polybenzimidazole membrane containing polymeric ionic liquid with high power density and enhanced proton conductivity for fuel cells

In phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes designed for high-temperature proton exchange membranes (HT-PEMs), increasing the PA doping is essential. Yet, excessive PA doping causes a decline in mechanical strength, which in turn affects the cell performance. We utilize a strategy that integrates elevated PA absorption, increased mechanical strength, and enhanced PA retention. An azide-type ionic liquid (IL) containing double bonds was synthesized and crosslinked with PBI via free radical polymerization reaction. In addition, the IL can also self-polymerize to form long-chain polymeric ionic liquid (PIL). Together, the two structures together form a semi-interpenetrating polymer network (sIPN) system, which has good mechanical properties. The synthesized alkaline ionic liquid can absorb and retain a large amount of PA through acid-base interactions and inter-ionic interactions. Consequently, the proton conductivity of the amino-type polybenzimidazole (AmPBI)-polymeric ionic liquid (PIL)-30 (where 30 stands for the wt% of IL) membrane in an anhydrous environment at 180 °C reached 138.2 mS cm−1. After PA retention test at 160 °C/0 % relative humidity (RH) for 240 h, the proton conductivity reached 99.4 mS cm−1 at 180 °C. The AmPBI-PIL-10 membrane exhibited a significant power density of 635.4 mW cm−2 at 160 °C. The AmPBI-PIL-X composite membranes exhibited exceptional performance.

High Surface Proton Conductivity of Epitaxial CeO2- δ Thin Film below Medium Temperature Range

Fluorite-type oxide such as Yttria-stabilized zirconia (YSZ) or doped-CeO2- δ ceramics are good electrolyte candidates for solid oxide fuel cells (SOFC) due to their high oxygen ion conductivity in high temperature range above 700 ºC[1]. Furthermore, porous and nanocrystalline CeO2- δ exhibit proton conduction at the surface below 100 °C[2]. This surface proton conduction is believed to the Grotthuss mechanism caused by the adsorption of water molecules. Since protons are produced by adsorbed water molecules and conduct through the layer of adsorbed water, oxygen vacancies and lattice constant are important parameters to enhance proton conduction. If high surface proton conduction can realize in CeO2- δ thin film, this may be more suitable than porous or nanocrystalline materials for new electrochemical devices and smart fuel cells.Recently, our group reported that the higher ion conductivity depends on the lattice constant and grain size for YSZ and Sm-doped CeO2- δ thin films[3,4]. However, the effect of crystallinity on the ion conductivity is not clarified. In this study, we have prepared the CeO2- δ thin films on YSZ (002) substrates by RF magnetron sputtering and probed their surface proton conduction below 300 °C in terms of electrical conductivity and electronic structure.The CeO2- δ ceramics target was prepared by solid-state reaction method. The CeO2- δ thin films with thicknesses of ~20 and ~120 nm were prepared by RF magnetron sputtering by adjust the deposition time. The sputtering conditions is followed; The base pressure was kept at 5.0×10-8 Torr and the deposition pressure was kept at 3.5 mTorr to control the Ar flow rate of ~2.67 sccm. The RF power was fixed at 30 W. The crystal and electrical structure of CeO2- δ thin films were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The electrical characteristics was evaluated by A.C. impedance method.The prepared CeO2- δ thin films on the YSZ substrates were due to the exhibited 200 and 400 peaks. Figure shows the Arrhenius plot of the conductivity of the as-deposited and wet-annealed CeO2- δ thin films, indicating thermally activated behavior in the medium temperature range but different behavior below 100 °C. The conducting carrier in the medium and room temperature range is considered to be oxide ion and proton, respectively. In this poster, we will show that the surface proton conduction of CeO2- δ thin film is closely related to the lattice distortion and oxygen vacancies concentration at the surface.

Sr Doped LaScO3 Thin Film As Cathodic Functional Layers for Ni-Fe Metal Supported Protonic Ceramic Fuel Cell Using BaZr0.44Ce0.36Y0.2O3 Film

Metal support proton conducting fuel cells (MS-PCFCs) is expecting as highly efficient and reliable power generation devices. In this study, porous Ni-Fe alloy support PCFCs was studied using BaZr0.44Ce0.36Y0.2O3 (BZCY) film prepared by pulsed laser deposition (PLD) method. For increasing power density, the effects of the La(Sr)ScO3 (denoted LSSc) at the cathodic interlayer were studied. BZCY film was deposited on dense NiO-NiFe2O4 oxide support by PLD, followed LSSc is deposited as a cathode functional layer (CFL). Sm0.5Sr0.5CoO3 (SSC) was used for the cathode, and then NiO-NiFe2O4 was reduced to obtain the porous metal substrate. Humidified H2 and O2 were used for fuel and oxidant, respectively. Metal support BZCY cell was successfully prepared, and open circuit potential (OCV) and maximum power density were 0.99 V and 69 mW/cm2, respectively at 600 ºC. So reasonable power density was achieved on the Ni-Fe support BZCY film. The main potential drop is occurred by ohmic resistance. Effects of the cathodic functional layer were studied, and it was found that La(Sr)ScO3 film at the interlayer between BZCY and SSC was highly effective for increasing the power density of the cell by decreasing IR loss and overpotential. The optimization of LSSc film was performed and the optimum Sr amount was 15 wt % in LSSc film and the thickness was 200 nm. The power density of MS-PCFCs with LSSc15 CFL was 405 mW/cm2 and an open-circuit voltage (OCV) was ca.1.1 V at 600 ºC, as shown in Figure 1. Due to enhanced proton conductivity, interfacial resistance and cathodic overpotential were also decreased. Insertion of LSSc CFL is highly effective for improving the performance of MS-PCFCs.Acknowledgment; Part of this study was financially supported by New Energy and Industrial Technology Development Organization (NEDO, JPNP20003), JapanReference[1] H. Sumi, H. Shimada, K. Watanabe, Y. Yamaguchi, K. Nomura, Y. Mizutani, R. M. Matsuda, M. Masashi, K. Yashiro, T. Araki, Y. Okuyama, J. Power Sources 2023, 582, 233528[2] A,Y. Stroeva, and V. P. Gorelov. Russian Journal of Electrochemistry 2012, 48, 1079-1085 Figure 1

(Invited) Improving the Stability and Transport Properties of a High Concentration of Protons in Phosphate Glass at Intermediate Temperatures

Fuel cells that operate at around 300 °C are expected as the next-generation fuel cells that can use liquid organic hydrogen carriers, such as methanol and methylcyclohexane, as fuel directly. Because of the lack of available solid electrolytes working at this temperature range, there is no fuel cell systems available at this temperature. Therefore, new electrolytes are currently being extensively investigated.Since the discovery of proton conductivity in phosphate glasses by Namikawa et al. in 1966, their proton conductivity has been investigated for applications in electrochemical devices such as fuel cells. Because conventional phosphate glasses could not hold proton carriers at temperatures above 250 °C, they were not suitable as an electrolyte for fuel cells operating at 300 °C. The reason why the glass cannot hold proton carriers at elevated temperatures is that the protons in glass exist predominantly as molecular water, which is readily released outside the glass at elevated temperatures. This limitation has recently been overcome by a proton injection method into phosphate glasses termed as alkali-proton substitution (APS), where the sodium ions in glass are electrochemically substituted with protons at high temperature (Fig. 1(a)). [1] A variety of glasses have been discovered that have high proton conductivity using APS (Fig. 1(b)). For examples, 36HO1/2–4NbO5/2–2BaO–4LaO3/2–4GeO2–1BO3/2–49PO5/2 glass exhibits high proton conductivity of 2 mScm−1 at 300 °C. [2] In order to achieve the conductivity higher than 10 mScm-1 required for practical fuel cell applications, it is necessary to further improve the stability and conductivity of proton carriers.Considering the glass formation range and the proton carrier density, the appropriate composition of the glass is around metaphosphate consisting of chain-type phosphate ions, (PO3 -)n. The deprotonation of glass fabricated using APS occurs through a dehydration-condensation reaction; thus, the migration or diffusion of PO4 tetrahedra is involved. Based on this, suppressing the viscous flow of the glass and its melt is an effective way to avoid deprotonation of the glass and its melt. Cross-linking the chain-type phosphate ions with heteroatoms that form covalent bonds with oxygen atoms is one of the ways to suppress viscous flow. Regarding proton transport, it is comprised of two fundamental processes: dissociation of the O-H bond and migration of the mobile proton; therefore, to enhance proton conductivity, controlling the strength of the O-H bond and migration of mobile protons are necessary. The strength of the O-H bond can be controlled by the bonding character of the P-O bond. The migration of mobile protons can be enhanced by enhancing the proton migration between the chain-type phosphate ions. Recently, it has been found that cross-linking between chain-type phosphate ions by heteroatoms that form a coordination polyhedron possessing non-bridging oxygen facilitates proton migration between phosphate ions. Based on these understanding, proton-conducting phosphate glass electrolytes that achieve 10 mScm-1 at 300 °C are being explored.The recent understandings mentioned above will be presented with specific examples.

Cellulose-Based Crosslinked and Reinforced Sulfonated Poly(ether ether ketone) Membranes for Robust Proton Exchange Membranes in Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) are a promising clean energy solution due to their high efficiency and eco-friendly operation. Central to their function is the proton exchange membrane (PEM), typically composed of perfluorosulfonic acid (PFSA) ionomers like Nafion and Aquivion. However, challenges such as cost, gas crossover, and limited temperature range persist. To address these, researchers explore hydrocarbon (HC)-based polymers like sulfonated poly(ether ether ketone) (SPEEK), prized for cost-effectiveness and stability. However, HC-based polymers suffer from issues like unstable mechanical behavior and reduced proton conductivity under low humidity, necessitating further development for practical application.In this study, we propose two approaches to overcome these drawbacks of HC-based PEMs. Firstly, we prepare crosslinked SPEEK membranes with cellulose acetate to enhance proton conduction under low RH conditions and stabilize membrane properties. The crosslinked structure of SPEEK/cellulose membranes is investigated using small-angle X-ray scattering, atomic force microscopy, and transmission electron microscopy. Additionally, we incorporate cellulose-based nanofibers obtained by electrospinning as a reinforcing substrate, enhancing the interaction between the SPEEK matrix and cellulose nanofiber filler. This results in a dense membrane without voids, effectively preventing gas crossover and improving membrane robustness. These investigations using cellulose-containing SPEEK membranes lead to enhanced power density and durable operation of fuel cells, particularly at low RH conditions.

Effect of Y Doping on Proton Conductivity of BaCo0.4Fe0.4Zr0.2-XYxO3-Δ (BCFZY) Proton Ceramic Fuel Cell (PCFC) Cathodes

Solid oxide fuel cells (SOFCs) are recognized as highly efficient renewable energy devices. However, their high operating temperatures (800–1000°C) present severe challenges, including material degradation and reduced energy conversion efficiency. Protonic ceramic fuel cells (PCFCs) have been developed to address these issues by operating at lower temperatures (400–700°C). PCFCs utilize proton conduction in oxide, which has a lower migration barrier than the oxygen ion conduction in SOFCs, making them promising for high performance at reduced temperatures. Nevertheless, current PCFC performance still falls short of SOFC performance, primarily due to sluggish oxygen reduction reaction (ORR) kinetics at the cathode perovskite materials. Enhancing the reaction kinetics necessitates the development of a cathode with high proton conductivity, which can broaden the reaction area within the cathode material. Doping with yttrium (Y) in perovskite material has been a potential solution for enhancing proton conductivity in cathode materials. Y doping in BaZrO3-based electrolytes has successfully led to the development of fast proton-conducting electrolytes for PCFCs. Y doping has also been introduced to the cathode perovskite material, BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY), by substituting Y for Zr atoms in BaCo0.4Fe0.4Zr0.2O3-δ (BCFZ) materials. BCFZY has shown potential as a cathode material aiming for high proton conductivity. It demonstrates superior performance in reducing oxygen while concurrently conducting electrons, oxygen ions, and protons. However, the exact effects of Y doping on BCFZY performance are not fully understood, even though research has indicated that the amount of Y doping in BCFZY significantly influences cell performance, including proton conductivity and area-specific resistance (ASR). In this study, we examined the effect of Y doping on the proton conductivity of BCFZY material. The critical question is whether Y doping affects proton diffusion or proton concentration, the main components of proton conductivity. To analyze proton diffusion, we employed density functional theory (DFT) to investigate the impact of Y doping on the proton self-diffusion coefficient. For proton concentration, we applied thermodynamics and defect models to assess the effects of Y doping. Finally, we validated and refined our findings using proton conductivity data from our experimental collaborators, Duffy et al. Our results indicate that Y doping in the BCFZY system slightly impacts proton diffusion, alters the proton uptake mechanism, and can significantly increase hydrogen concentration. This study provides insights for designing high-performance BCFZY materials or perovskite materials for PCFCs that contain redox-inactive acceptor dopants like Y.

Composite membrane comprised of SnO2 nanoparticles loaded intercrosslinked network of Polyvinylalcohol and Chitosan for proton transfer membrane fuel cells

ABSTRACT 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.

Polymeric ionic liquids and piperidinium synergistically improve proton conductivity and acid retention of polybenzimidazole-based proton exchange membranes

Amino-type polybenzimidazole is prepared, then ionic liquid with three nitrogen positive sites ([CTDTr]Br3) is polymerized into polymeric ionic liquids (PILs) by in-situ radical polymerization, and AmPBI-CTDTr-Px membranes were prepared by piperidinium (PPd) and [CTDTr]Br3 combination to cross-linked with AmPBI. Following treatment with KOH and phosphoric acid (PA), the ion pairs (N+ - H2PO4−) generated in the composite membrane system can enhance proton conductivity and facilitate proton transport. The AmPBI-CTDTr-Px membranes shown exceptional PA retention as a result of the alkaline properties of both [CTDTr]Br3 and PPd, which can engage in acid-base interactions with phosphoric acid. Specifically, the proton conductivity of AmPBI-CTDTr-P5 at 180 °C is 129.7 mS cm−1, which is 2.52 times that of pure membranes. Acid retention of AmPBI-CTDTr-P5 at 80 °C/40 % RH and 160 °C are 64.4 % and 84 %.

Hydrocarbon-based composite membranes containing sulfonated Poly(arylene thioether sulfone)-grafted 2D crown ether framework coordinated with cerium ions for PEMFC applications

We propose a novel strategy to develop sulfonated poly(arylene ether sulfone) (SPAES) composite membranes that can simultaneously improve the physicochemical stability and proton conductivity of hydrocarbon-based membranes for PEMFC applications. This strategy involves the use of a sulfonated poly(arylene thioether sulfone)-grafted 2D crown ether framework coordinated with cerium3+ ions (SATS–C2O–Ce) as a promising filler material. SATS-C2O, a highly sulfonated polymer-grafted 2D framework containing crown ether holes in its skeletal structure, was prepared via self-condensation using halogenated phloroglucinol as a multifunctional building unit to form C2O, followed by condensation using SATS to graft the sulfonated polymer onto its edge. Ce3+ ions were directly coordinated within the crown ether holes of SATS-C2O via a simple doping process using aqueous Ce solution. The SPAES composite membranes containing SATS–C2O–Ce (SPAES/SATS–C2O–Ce) exhibited exceptional dimensional stability and mechanical toughness. The remarkable chemical stability of SPAES/SATS–C2O–Ce compared to that of pristine SPAES and SPAES/Ce (containing the same amount of Ce3+ ions but without SATS-C2O) was attributed to the well-dispersed state of Ce3+ ions within the SPAES matrix. Furthermore, the enhanced proton conductivity of SPAES/SATS–C2O–Ce surpassed those of pristine SPAES, SPAES/C2O, and SPAES/Ce by the formation of additional proton-conducting channels provided by the sulfonic acid groups of SATS–C2O–Ce, along with the improved water uptake capability of SPAES.

Research Progress in Enhancing Proton Conductivity of Sulfonated Aromatic Polymers with ZIFs for Fuel Cell Applications

The escalating global temperatures and their adverse effects underscore the growing imperative for the widespread adoption of clean fuels, notably hydrogen. Proton Exchange Membrane Fuel Cells (PEMFC) emerge as a pivotal green energy technology, facilitating electricity and water generation. The optimization of PEMFC efficiency hinges on the judicious selection and fabrication of polymer membranes. Within innovative materials, Zeolitic Imidazolate Frameworks (ZIFs) represent a novel subclass within the expansive family of Metal-Organic Frameworks (MOFs). ZIFs exhibit promising potential in PEMFCs, owing to their distinctive properties such as a substantial contact surface, inherent porosity, and a sizable pore volume. This comprehensive review delves into composite membranes featuring ZIFs, shedding light on their chemical and thermal attributes. Additionally, the exploration extends to elucidating the diverse applications of ZIF compounds, accompanied by an in-depth discussion of selected chemical and thermal properties inherent to ZIF compounds. Incorporating ZIFs into various polymers yielded intriguing outcomes, demonstrating a notable enhancement in proton conductivity. The compilation of this review aims to provide researchers with foundational insights into the realm of ZIFs, serving as a valuable resource for future investigations and advancements in the field.

High-performance PVdF-HFP/PEG-IL composites: The combined effects of PEG and ionic liquid on proton conductivity and dielectric characteristics

This study explores the influence of varying polyethylene glycol (PEG) concentrations on the properties of PVdF-HFP/PEG-IL polymer composites through comprehensive characterization techniques, including FTIR, SEM, TGA, DMA, XRD and the detailed assessments of proton conductivity, dielectric properties, and relaxation dynamics. In terms of conductivity, the addition of PEG markedly improves proton conductivity. The PVdF-HFP/PEG40-IL composite exhibits the highest conductivity, reaching 1.96 × 10⁻2 S/m at 1 MHz and 300 K, and increasing to 4.27 × 10⁻2 S/m at 420 K. Dielectric properties show that the dielectric constant (ε′) increases with PEG content at low frequencies but decreases at higher frequencies due to reduced ionic polarization. Notably, PVdF-HFP/PEG40-IL achieves a dielectric constant of 3.39 × 106 at 20 Hz, which decreases to 30.34 at 1 MHz. Dielectric loss (ε'') also rises with temperature, with PVdF-HFP/PEG40-IL demonstrating the highest dielectric loss, indicative of superior proton conduction and polarization capabilities. Relaxation dynamics, as evidenced by tanδ, reveal that relaxation time significantly decreases with both increased PEG content and temperature, dropping from 1.06 × 10⁻4 s to 2 × 10⁻6 s as PEG concentration increases from 10 % to 40 %. This reduction in relaxation time correlates with enhanced proton conductivity and faster dipole relaxation, indicating PEG effect as a plasticizer that reduces polymer viscosity and improves ion transport. In conclusion, incorporating PEG into PVdF-HFP-IL composites leads to substantial improvements in proton conductivity, dielectric properties, and relaxation dynamics. The results highlight the crucial role of PEG in optimizing the performance of polymer electrolyte composites, making them effective candidates for advanced energy storage and conversion applications.

Potential of kaolin as filler in Nafion composite membranes for PEM fuel cells

Nafion is one of the polymer materials used as a polymer exchange membrane (PEM) in fuel cells due to its high proton conductivity, chemical stability, and fuel cell performance. However, Nafion membranes still have notable disadvantages, such as decreased proton conductivity at high temperatures and low humidity. One of the methods applied to overcome these limitations is to add inorganic compounds to the Nafion matrix. In this study, kaolin, a hygroscopic clay, was incorporated into Nafion for the first time to enhance proton conductivity of the membrane. Kaolin-doped composite membranes (5 %, 10 %, and 15 % kaolin by weight) were produced through the solution casting method and analyzed using various characterization techniques. The synthesized membranes exhibited significantly higher water uptake, lower swelling, higher proton conductivity, and better mechanical properties compared to recast Nafion. Among all composite membranes, Nafion-Kaolin-15 demonstrated a proton conductivity of 0.330 S/cm, which is a remarkable enhancement of 1.43 times compared to recast Nafion. These findings revealed the potential of kaolin-doped Nafion membranes for future applications in PEMFCs.

Regulating Molecular Interactions in Polybenzimidazole Membrane for Efficient Vanadium Redox Flow Battery.

The tightly bonded structure of polybenzimidazole (PBI) membrane is the origin of its poor proton conductivity, which severely hinders achieving a cost-effective membrane for vanadium redox flow battery (VRFB). It desires a strategy to relax the membrane structure to significantly improve the proton conductivity and maintain its structure stability. Therefore, this work proposes a novel strategy through regulating molecular interactions within PBI membrane to loosen up the structure of PBI membrane and dramatically enhance the proton conductivity. The interactions in PBI membrane are switched by DMSO/water and acid through sequentially treating membrane with these solutions. The efficient PBI membrane prepared using this strategy demonstrates an outstanding performance for VRFB, with the proton conductivity enhanced by 3850 % (from 1.9 to 76.3 mS cm-1), and VRFB achieves a high energy efficiency of 80.5 % under 200 mA cm-2. More importantly, this work shed lights on the structure-property relationship of PBI membrane, and the mechanism in enhancing proton conductivity is unraveled, which is of great significance for the development of VRFB membranes.