Hybrid Proton Exchange Membrane Research Articles

Amino–Functionalized Multi–walled Carbon Nanotube/SPEEK Hybrid Proton Exchange Membrane for Iron–chromium Redox Flow Battery**

AbstractIn the field of iron–chromium redox flow battery (ICRFB), the optimal doping ratio of the amino–functionalized multi–walled carbon nanotube (MWCNT−NH2) blended with SPEEK as hybrid proton exchange membrane (PEM) is determined to be 2 wt % by series tests. The ICRFB single–cell containing the S/MWCNT−NH2−2 PEM was tested and compared with the Nafion 212 and original SPEEK PEMs. It is worth noting that the single–cell containing S/MWCNT−NH2–2 exhibits significantly higher coulombic efficiency (CE : 96.06 %) and energy efficiency (EE : 88.68 %) under 40 mA cm−2 than that of the Nafion 212 (EE : 82.83 %, CE : 88.9 %). Differing from the original SPEEK PEM, it also exhibits higher EE (82.04 %) than the Nafion 212 (81.09 %) at 100 mA cm−2. During the self–discharge test, the lower permeability of iron/chromium ions through S/MWCNT−NH2–2 PEM also allows for a longer self–discharge time than the other two single–cells. Additionally, the single–cell containing S/MWCNT−NH2–2 showed a smaller decay range of EE (from 82.67 % to 77.36 %) and more discharge capacity retention (48 %) than that of the Nafion 212 (EE : from 82.64 % to 75.01 %, discharge capacity retention: 18 %) after 100 cycles, which suggests that the hybrid SPEEK PEM with optimal content of MWCNT−NH2 has a great potential to replace Nafion PEMs in the large‐scale commercialization of ICRFB.

Hybrid Membrane of Sulfonated Poly(aryl ether ketone sulfone) Modified by Molybdenum Clusters with Enhanced Proton Conductivity.

Developing novel proton exchange membranes (PEMs) with low cost and superior performance to replace Nafion is of great significance. Polyoxometalate-doped sulfonated poly(aryl ether ketone sulfone) (SPAEKS) allows for the amalgamation of the advantages in each constituent, thereby achieving an optimized performance for the hybrid PEMs. Herein, the hybrid membranes by introducing 2MeIm-{Mo132} into SPAEKS are obtained. Excellent hydrophilic properties of 2MeIm-{Mo132} can help more water molecules be retained in the hybrid membrane, providing abundant carriers for proton transport and proton hopping sites to build successive hydrophilic channels, thus lowering the energy barrier, accelerating the proton migration, and significantly fostering the proton conductivity of hybrid membranes. Especially, SP-2MIMo132-5 exhibits an enhanced proton conductivity of 75mScm-1 at 80°C, which is 82.9% higher than pristine SPAEKS membrane. Additionally, this membrane is suitable for application in proton exchange membrane fuel cells, and a maximum power density of 266.2mWcm-2 can be achieved at 80°C, which far exceeds that of pristine SPAEKS membrane (54.6mWcm-2). This work demonstrates that polyoxometalate-based clusters can serve as excellent proton conduction sites, opening up the choice of proton conduction carriers in hybrid membrane design and providing a novel idea to manufacture high-performance PEMs.

Construction of proton transport channels and performance Modulation of phosphotungstic acid hybrid proton exchange membranes for direct methanol fuel cell

Serving as the central part of a direct-methanol fuel cell (DMFC), a proton exchange membrane (PEM) is used to conduct protons, isolate electrons and fuel, and ensure the proper operation of the battery. The novel hybrid proton exchange membrane (PEM) proposed in the present work is comprised of polyethyleneimine (PEI) and polyvinyl alcohol (PVA) doped with phosphotungstic acid (PWA). PEI provides numerous locations for PWA anchoring and allows for the creation of efficient and continuous proton transport channels over long distances. PEI can be cross-linked with PVA through Glutaraldehyde (GA), which not only suppresses the disadvantage of PVA as a proton exchange membrane that tends to swell after water absorption and leads to deformation, but also the hydrogen-bonded network structure formed after cross-linking is conducive to proton hopping conduction, which synergistically improves the proton conduction rate of PEMs. A good compromise between the amount of PWA doping and the electrochemical properties of PEMs can result in optimal performance. Compared to other reported PEMs that use hetero-poly acids or other inorganic acids, PVA/PEI-PWA2 PEM exhibits superior overall properties. The highest proton conductivity of PVA/PEI-PWA2 is 124.3 mS cm−1 at 80 °C, the highest peak power density can reach 109.8 mW cm−2 (301.8 mA cm−2) at 60 °C, and the methanol barrier performance and selective permeability are 4.95 × 10−7 cm2 s−1 and 12.32 × 104 S s cm−3, respectively.

Improved performance of lanthanide-doped UIO-66/Nafion hybrid proton exchange membrane for water electrolyzer

Incorporating metal-organic frameworks (MOFs) especially the ones with protic functional groups into proton exchange membrane (PEM) can effectively improve its proton conductivity. Lanthanide MOFs (Ln-MOFs) have been recognized as more potential candidates exhibiting proton dissociation capability. However, the performance of PEM upon integrating Ln-MOFs in water electrolyzer has yet to be investigated. In this study, Nafion composites with different loadings of lanthanide Ce-UiO-66 were prepared, characterized and tested by comparing with the non-lanthanide Zr-UiO-66. It was revealed that the proton conductivity of Ce-UiO-66/Nafion composite membrane was higher than pristine Nafion and Zr-UiO-66/Nafion membrane, which was attributed to the fact that the Ce-UiO-66 doping contributed to the construction of the hydrogen-bonded network to enhance the proton conductivity. At 3 wt% Ce-UiO-66 doping, the proton conductivity of the composite membrane can reach 124.45 mS/cm, which is significantly improved by 17 % compared with Zr-UiO-66/Nafion. Such a trend is mainly contributed by the lower proton affinity and proton transfer capability of Ce atoms in Ce-UiO-66, and the higher number of water molecules around Ce atoms favors the reduced tortuosity of the proton conduction pathway in membranes. Single electrolytic cell tests demonstrated the enhancement of electrolysis efficiency upon Ce-UiO-66 doping was improved from 58.77 % to 65.37 % at a current density of 2 A cm−2.

Adjusting structure-activity relationship to obtain hybrid proton exchange membrane with enhanced transport efficiency by introducing functionalized nano-coated MOFs

Designing proton exchange membranes (PEMs) with high H+ conductivity and good dimensional stability has been a challenge. The porous structure of ZIF-8 could load ionic liquids (IL) (ZIF-8@IL). The ZIF-8@IL was coated by sulfonated polydopamine (SPDA), then ZIF-8@IL-SPDA as proton conductors was fabricated. ZIF-8@IL-SPDA would not lose in water environment like small molecule proton conductors (such as sulfuric acid, phosphoric acid, imidazole, etc.). The different loadings of ZIF-8@IL-SPDA were introduced into sulfonated poly (aryl ether ketone sulfone) containing fluorene groups (F-SPAEKS). The novel composite PEMs was investigated. The prepared hybrid matrix membrane with optimum ZIF-8@IL-SPDA doping content (1.5 wt%) showed the highest H+ conductivity of 149.87 mS cm−1 at 80 °C. In addition, a maximum peak power density of 818 mW cm−2 was achieved in a single-cell performance test of this membrane. The good dispersion of ZIF-8@IL-SPDA nanoparticles in the F-SPAEKS matrix reduced the fuel cross-over flux to 2.15 mA cm−2. Therefore, the newly prepared hybrid matrix membranes were expected to be applied in proton exchange membrane fuel cells.

Covalent organic frameworks with flexible side chains in hybrid PEMs enable highly efficient proton conductivity.

Electrochemical hydrogen compression (EHC) is an emerging energy conversion technology. Proton exchange membranes (PEMs) with high proton conductivity and high mechanical strength are highly required to meet the practical requirements of EHC. Herein, ionic covalent organic frameworks (iCOFs) with tunable side chains were synthesized and introduced into the sulfonated poly (ether ether ketone) (SPEEK) matrix to fabricate hybrid PEMs. In our membranes, the rigid iCOFs afford ordered proton conduction channels, whereas the flexible side chains on iCOFs afford abundant proton conduction sites, adaptive hydrogen bonding networks, and high local density short hydrogen bonds for highly efficient proton transport. Moreover, the hydrogen bond interactions between the side chains on iCOFs and the SPEEK matrix enhance the mechanical stability of membranes. As a result, the hybrid PEM acquires an enhanced proton conductivity of 540.4 mS cm-1 (80 °C, 100%RH), a high mechanical strength of 120.41 MPa, and a superior performance (2.3 MPa at 30 °C, 100%RH) in EHC applications.

Development of film nanocomposite membranes from nanocrystalline cellulose combined with reduced graphene oxide or graphene oxide: Evaluation of potential applications in proton exchange membranes

Raw materials from renewable sources are actually of interest to design materials with functional properties for use in the proton exchange membranes (PEMs) field, and thus replace the costly based-Nafion PEMs. Corncob (CC), the by-product of harvesting grains, is rich in lignocellulose polymers, which can be extracted and processed through pretreatments and hydrolysis chemical reactions to remove hemicellulose (H), lignin (L) and amorphous cellulose (C) to obtain nanocrystalline cellulose (CNC). The electrochemical, mechanical and water up-take properties of CNC can be adjusted by adding reduced graphene oxide (rGO) or graphene oxide (GO) promoting a synergistic effect among the components to increase the proton conductivity and improve the operating temperature of PEMs. This work deals with analyzing the pretreatment and acid hydrolysis (1:100 ratio, 1 h) through monitoring structural phases after the elimination of H, L and amorphous C; and the effect of temperature (50, 60 and 70 °C) to obtain CNC on crystallinity and crystal/fiber sizes is studied. The hydrolysis time (1 and 1.5 h) at 60 °C was also considered. The Results indicate the coexistence of phases I-α, I-β and II after pretreatments and the disappearance of phase II after acid hydrolysis. The increase in temperature was key inducing high crystallinity percentages (from 52% to 68%), crystallite sizes (from 2 to 4 nm) and diameter of microfiber (from 18 to 25 nm). Hybrid PEMs based on optimal CNC samples (60 °C, 1 h and 1.5 h) with GO and rGO (0.5 and 1.5 wt%) were processed via casting knife to evaluate moisture uptake as well as structural, mechanical and electrochemical performance. A shorter hydrolysis time (CNC1.0 h) induces a higher hardness value compared to CNC1.5 h; the optimal sample was found with rGO (CNC1.0 h:rGO1.5 wt%). Hydrogen bonding between GO or rGO was found to be key improving the water adsorption capacity and dimensionality at 60 °C (CNC1 h:GO 0.5 wt% and CNC1.5 h:rGO1.5 wt%). The impedance evaluated at 50, 60, 65 and 70 °C indicates a decrease with temperature. CNC1.5 h, had better impedance values more than CNC1.0 h. The greatest proton conductivity was found for CNC1.5 h:rGO 0.5 wt%. Therefore, these proposed and ecofriendly CNC:rGO and CNC:GO materials can fulfil the required properties for PEMs applications to replace Nafion membranes.

Design of a Fuel Cell/Battery Hybrid Power System for a Micro Vehicle: Sizing Design and Hydrogen Storage Evaluation

This work focuses on the design of a hybrid proton exchange membrane fuel cell (PEMFC) solution for any micro vehicle such as an unmanned aerial vehicle (UAV). A hydrogen fuel cell can provide extended operation, low emissions, and a highly efficient form of energy storage compared with alternative methods, while a battery can be used as an additional energy storage system to support the transient and higher loads required by the UAV, which are not suitable for normal fuel cell operation. The choice of hydrogen storage is one of the main challenges in using hydrogen as an energy carrier. The current study discusses a range of hydrogen storage technologies and provides a methodology for selection for a given application. A sizing design methodology for a hybrid fuel cell system is proposed. Then, it is applied to a case study to demonstrate its implementation.

Proton exchange membranes for polymer electrolyte fuel cells: An analysis of perfluorosulfonic acid and aromatic hydrocarbon ionomers

The design of proton-exchange membranes (PEMs) for high-performance, durable fuel cells and related electrochemical devices requires a delicate balance between high ion-exchange capacity and proton conductivity, while ensuring robust mechanical properties and preserving dimensional, chemical and thermal stability. In addition, low species crossover is desirable to reduce hydrogen peroxide formation. Ionomers used in PEMs can be classified into two main groups: (i) perfluorosulfonic acid (PFSA) polymers, and (ii) aromatic hydrocarbon (HC) polymers. In this work, an analysis of key characteristics of both PEM types is presented, including water uptake, proton conductivity, water transport properties, thermal conductivity, permeability, mechanical properties and chemical and thermal stability, among others. Comparatively, PFSA-based PEMs are undoubtedly the commercial standard due to its proven high proton conductivity and good chemical stability, even though PTFE-reinforced aromatic HC-based PEMs have also started to be commercialized recently. In the last decades, a growing trend is identified toward the development of hybrid and composite ultra-thin PEMs (5–20 μm in thickness) with tailored properties, e.g., incorporating microporous fillers to enhance water uptake and layered reinforced microstructures to improve mechanical properties and chemical stability. PEM design is to be accomplished in an environmentally friendly circular economy with facilitated recycling and re-utilization.

Self-sustainable, self-healable sulfonated graphene oxide incorporated nafion/poly(vinyl alcohol) proton exchange membrane for direct methanol fuel cell applications

Nafion, a perfluorosulfonic acid polymer, has been the standard membrane material for direct methanol fuel cells (DMFCs) due to its proton-carrying capabilities, despite its shortcomings as a methanol barrier. To attain self-healing and methanol-blocking properties, the incorporation of poly(vinyl alcohol) (PVA) polymer into Nafion was pursued. However, this strategy resulted in low proton conductivity. Thus, acid functional groups were added to a secondary modifier to boost proton conductivity. In this work, sulfonated graphene oxide (SGO) was assembled with Nafion and PVA through a simple freezing-thawing method to demonstrate a self-healable proton exchange membrane (PEM) without compromising the proton conductivity of Nafion. The synergistic effect of SGO in methanol-blocking and proton transport successfully strode over recast Nafion by hampering 33.2 % of methanol permeation and increasing 19.5 % of proton conductivity. As a result, the selectivity of the best hybrid PEM (N/PVA/SGO1.0) was increased by 1.8 times in comparison to recast Nafion. A single cell passive DMFC made using the novel hybrid membrane exhibited a power density of 6.07 mW cm−2 at a current density of 26.48 mA cm−2, and an open circuit voltage of 0.55 V at room temperature using 4 M methanol. This performance was essentially higher than that achieved by recast Nafion and commercial Nafion 117. The N/PVA/SGO1.0 hybrid membrane also showed remarkable self-healing properties, with 89 % recovery of methanol blocking function through reversible hydrogen bonding, illustrating its tremendous sustainable potential for use in DMFCs.

Rational tailoring of architectures and microenvironment on MOFs/natural clay hybrid materials for efficiently boosted performance of hybrid proton exchange membranes

AbstractMetal–organic frameworks (MOFs) is now becoming the most fascinating conductive materials due to designable structure and pores at molecular level, and available crystal structure for the study of conduction mechanism. Nevertheless, comparing to the design of molecular structures of MOFs, the hybrid of MOFs with special micro/nano‐structured materials is considered to be a more effective approach for improved properties. In this study, the PAT@UiO‐66‐SO3H hybrid material was constructed with high conductive UiO‐66‐SO3H, a famous kind of MOFs, and polydopamine‐coated natural clay attapulgite (PAT), then the prepared hybrid material was blended with chitosan (CS) to prepare proton exchange membranes (PEMs). Owing to the special architectures and microenvironment, combining with the advantages of composition with UiO‐66‐SO3H and attapulgite, the prepared composite membranes showed considerable improved performances, including tensile strength, thermal and structural stability, fuel resistance ability, conduction and single cell performances. The CS/PAT@UiO‐66‐SO3H‐5 composite membrane exhibited the highly enhanced tensile strength of 67 MPa and improved thermal stability with Tg value of 235°C, as well as the lowest methanol crossover value of 1.2 × 10−6 cm2 s−1. Besides, the highest proton conductivity of 38.8 mS cm−1 at 80°C and power density of 37.9 mWcm−2 was achieved with CS/PAT@UiO‐66‐SO3H‐3 composite membrane, these performances were higher than pristine CS of 22.7 mS cm−1 and 32.2 mW cm−2 respectively. Our investigation reveals great application potential of MOFs based hybrid materials in fabricating of high performance composite PEMs.Highlights PAT@UiO‐66‐SO3H hybrid materials were constructed from MOFs and natural clay. The hybrid materials possessed special architectures and microenvironment. The PAT@UiO‐66‐SO3H introduced consecutive channels and proton sites. The hybrid membranes achieved excellent performances.

Bioinspired supramolecular macrocycle hybrid membranes with enhanced proton conductivity

AbstractEnhancing the proton conductivity of proton exchange membranes (PEMs) is essential to expand the applications of proton exchange membrane fuel cells (PEMFCs). Inspired by the proton conduction mechanism of bacteriorhodopsin, cucurbit[n]urils (CB[n], where n is the number of glycoluril units, n = 6, 7, or 8) are introduced into sulfonated poly(ether ether ketone) (SPEEK) matrix to fabricate hybrid PEMs, employing a nature-inspired chemical engineering (NICE) methodology. The carbonyl groups of CB[n] act as proton-conducting sites, while the host–guest interaction between CB[n] and water molecules offers extra proton-conducting pathways. Additionally, the molecular size of CB[n] aids in their dispersion within the SPEEK matrix, effectively bridging the unconnected proton-conducting sulfonic group domains within the SPEEK membrane. Consequently, all hybrid membranes exhibit significantly enhanced proton conductivity. Notably, the SPEEK membrane incorporating 1 wt.% CB[8] (CB[8]/SPEEK-1%) demonstrates the highest proton conductivity of 198.0 mS·cm−1 at 60 °C and 100% relative humidity (RH), which is 228% greater than that of the pure SPEEK membrane under the same conditions. Moreover, hybrid membranes exhibit superior fuel cell performance. The CB[8]/SPEEK-1% membrane achieves a maximum power density of 214 mW·cm−2, representing a 140% improvement over the pure SPEEK membrane (89 mW·cm−2) at 50 °C and 100% RH. These findings serve as a foundation for constructing continuous proton-conducting pathways within membranes by utilizing supramolecular macrocycles as fuel cell electrolytes and in other applications.

Evaluating the performance of hybrid proton exchange membrane for PEM water electrolysis

Owing to their attractive properties (e.g. reduced gas permeation, comparable proton conductivity, enhanced thermal stability, lower cost), hybrid nanocomposite membranes (HNC) are more attractive for proton exchange membrane water electrolysis (PEMWE). Compared to perfluoro sulfonic acid polymers, this study evaluated the interest in using an HNC membrane for PEMWE. Despite the bulk membrane exhibiting high chemical and mechanical instability (decreasing the cell performance), a multi-layer approach was adopted to increase its lifespan in PEMWE operation. Thus, different strategies for preparing Catalyst-Coated Membrane (CCM) with more than one PEM were investigated. The longevity of the HNC membrane is enhanced from a few hours to a few hundred hours by clamping it between two half-coated Nafion 212 membranes. The degradation mechanisms are discussed based on the physicochemical analysis of the membrane and its degradation products after electrolysis.

Application of Ionic Hydrogen-Bonded Organic Framework Materials in Hybrid Proton Exchange Membranes

Excellent and inexpensive materials with proton conductivity have far-reaching significance for the development of clean energy. In this paper, three ionic hydrogen-bonded organic frameworks (iHOFs) were synthesized using naphthalenedisulfonate derivatives with substituents at different positions and 1,1′-diamino-4,4′-bipyridylium. The hydrogen bond networks were formed by sulfonic acid groups and amino groups, while the addition of functional groups such as hydroxyl or amino groups can also enrich the hydrogen bonds, which also makes such iHOFs have high conductivity, in which iHOF-7 afforded the highest proton conductivity of 4.5 × 10–3 S·cm–1 at 100 °C, 85% relative humidity (RH). It is difficult for the crystalline materials to form a membrane, so we prepared the hybrid membranes of iHOF-7 using sulfonated poly (ether ether ketone) (SPEEK) or chitosan (CS) as the supporting polymeric matrix. At 85% RH and 100 °C, the highest proton conductivity of the 15%-iHOF-7/SPEEK composite membrane can reach 5.1 × 10–3 S·cm–1, and at 98% RH and 100 °C, the highest proton conductivity of 15%-iHOF-7/CS can reach to 5.7 × 10–3 S·cm–1.

Comprehensive assessment on a hybrid PEMFC multi-generation system integrated with solar-assisted methane cracking

A hybrid proton exchange membrane fuel cell (PEMFC) multi-generation system model integrated with solar-assisted methane cracking is established. The whole system mainly consists of a disc type solar Collector, PEMFC, Organic Rankine cycle (ORC). Methane cracking by solar energy to generate hydrogen, which provides both power and heat. The waste heat and hydrogen generated during the reaction are efficiently utilized to generate electricity power through ORC and PEMFC. The mapping relationships between thermodynamic parameters (collector temperature and separation ratio) and economic factors (methane and carbon price) on the hybrid system performance are investigated. The greenhouse gas (GHG) emission reductions and levelized cost of energy (LCOE) are applied to environmental and economic performance evaluation. The results indicate that the exergy utilization factor (EXUF) and energy efficiency of the novel system can reach 21.9% and 34.6%, respectively. The solar-chemical energy conversion efficiency reaches 40.3%. The LCOE is 0.0733 $/kWh when the carbon price is 0.725 $/kg. After operation period, the GHG emission reduction and recovered carbon can reach 4 × 107 g and 14,556 kg, respectively. This novel hybrid system provides a new pathway for the efficient utilization of solar and methane resources and promotes the popularization of PEMFC in zero energy building.

An ultrahigh conductivity and efficiency of SPEEK-based hybrid proton exchange membrane containing amphoteric GO-VIPS nanofillers for vanadium flow battery

Sulfonated poly(ether ether ketone) (SPEEK)-based hybrid membranes (S/GO-VIPS) have been fabricated by the solution blending method, which amphoteric GO-VIPS nanofillers prepared by grafting 3-(1-vinyl-3-imidazole) propane sulfonate (VIPS) onto graphene oxide (GO) flake. With various GO-VIPS contents changing from 1 to 10 wt% in the S/GO-VIPS membranes, the interfacial interaction between SPEEK and GO-VIPS contributes to enhanced membrane structures and performance. Against pristine SPEEK (3.9 × 103 S min cm−3) and Nafion 117 (4.0 × 103 S min cm−3), S/GO-VIPS-5 gives the highest ion selectivity at 24.4 × 103 S min cm−3, demonstrating the amphoteric GO-VIPS nanosheets afford a superior vanadium ion resistance and proton conductivity. At 100–200 mA cm−2 current density, S/GO-VIPS-5 presents excellent coulombic efficiency (97.4–99%), energy efficiency (78.9–66.3%), and self-discharge time (78 h), which is better than that of SPEEK and Nafion 117, respectively. Further cycling at 100 mA cm−2 for 350 times, its energy efficiency maintains at 80%, confirming its excellent structural stability and chemical stability. Combining with the physical barrier and the amphoteric acid-base functional groups of the GO-VIPS nanosheets, the increased proton conductivity and ion selectivity, and the decreased permeability of SPEEK-based membranes are well-regulated, demonstrating a promise in developing high-performance proton exchange membrane for vanadium flow battery applications.

Preparation of phosphotungstic acid hybrid proton exchange membranes by constructing proton transport channels for direct methanol fuel cells

For direct methanol fuel cells (DMFCs), a unique hybrid proton exchange membrane (PEM) made of polyvinyl alcohol (PVA) and quaternized polyethyleneimine (QPEI) is presented. Employing QPEI as an anchoring agent is advantageous for enhancing the compatibility of the organic-inorganic interface when phosphotungstic acid (PWA) is used as the proton conductor on the assumption that the leakage of PWA is successfully reduced. Utilizing polymers as a substrate reduces the high solubility of PWA in water owing to hydrogen bonding and electrostatic interactions. Additionally, PWA performs the function of successive proton transport channels in the optimized PVA-QPEI-2 PEM, resulting in a maximum proton conductivity of 194.5 mS cm−1 and residual proton conductivity of more than 80% after 30 days of soaking in deionized water at 80 °C. Furthermore, the fuel cell assembled with PVA-QPEI-2 PEM delivers a peak power density of 147.2 mW cm−2 at 60 °C and 40% relative humidity. Noteworthily, this organic-inorganic hybrid PEM containing PWA as a proton carrier is fabricated by a remarkably simple method, which has a methanol permeability that is an order of magnitude less than the Nafion® used in commercial applications, demonstrating its competitive potential for application in DMFCs.

Advanced Functional Hybrid Proton Exchange Membranes Robust and Conductive at 120 °C

AbstractProton‐exchange membrane fuel cell vehicles offer a low‐carbon alternative to traditional oil fuel vehicles, but their performances still need improvement to be competitive. Raising their operating temperature to 120 °C will enhance their efficiency but is currently unfeasible due to the poor mechanical properties at high temperatures of the state‐of‐the‐art proton‐exchange membranes consisting of perfluorosulfonic acid (PFSA) ionomers. To address this issue, xx designed composite membranes made of two networks: a mat of hybrid fibers to maintain the mechanical properties filled with a matrix of PFSA‐based ionomer to ensure the proton conductivity. The hybrid fibers obtained by electrospinning are composed of intermixed domains of sulfonated silica and a fluorinated polymer. The inter‐fiber porosity is then filled with a PFSA ionomer to obtain dense composite membranes with a controlled fibers‐to‐ionomer ratio. At 80 °C, these obtained composite membranes show comparable performances to a pure PFSA commercial membrane. At 120 °C however, the tensile strength of the PFSA membrane drastically drop down to 0.2 MPa, while it is maintained at 7.0 MPa for the composite membrane. In addition, the composite membrane shows a good conductivity of up to 0.1 S cm−1 at 120 °C/90% RH, which increases with the ionomer content.

Porous organic polymer with high-density phosphoric acid groups as filler for hybrid proton exchange membranes

Developing sulfonated poly (ether ether ketone) (SPEEK)-based proton exchange membrane with both high proton conductivity and robust mechanical stability is desired for proton exchange membrane fuel cell (PEMFC). Here, a type of phosphoric acid porous organic polymer (PAPOP) with high‐density phosphoric acid (-PO3H2) groups and microporous structure was synthesized and incorporated into SPEEK matrix. The porous skeleton bonding -PO3H2 groups of PAPOP reduced the proton transfer activation energy by providing additional proton conduction pathways. The rigid backbone of PAPOP and its good compatibility with SPEEK increased the mechanical strength of the membrane. The hybrid membrane achieves greatly enhanced proton conductivity up to 417.0 mS cm−1 (80 °C, 100% RH) and high tensile strength of 120.6 MPa. The maximum power density of fuel cell with the hybrid membrane exhibits two times increase compared with the control membrane.

Supramolecular Anchoring of Polyoxometalate Amphiphiles into Nafion Nanophases for Enhanced Proton Conduction.

Advanced proton exchange membranes (PEMs) are highly desirable in emerging sustainable energy technology. However, the further improvement of commercial perfluorosulfonic acid PEMs represented by Nafion is hindered by the lack of precise modification strategy due to their chemical inertness and low compatibility. Here, we report the robust assembly of polyethylene glycol grafted polyoxometalate amphiphile (GSiW11) into the ionic nanophases of Nafion, which largely enhances the comprehensive performance of Nafion. GSiW11 can coassemble with Nafion through multiple supramolecular interactions and realize a stable immobilization. The incorporation of GSiW11 can increase the whole proton content in the system and induce the hydrated ionic nanophase to form a wide channel for proton transport; meanwhile, GSiW11 can reinforce the Nafion ionic nanophase by noncovalent cross-linking. Based on these synergistic effects, the hybrid PEMs show multiple enhancements in proton conductivity, tensile strength, and fuel cell power density, which are all superior to the pristine Nafion. This work demonstrates the intriguing advantage of molecular nanoclusters as supramolecular enhancers to develop high-performance electrolyte materials.