Increase In Proton Conductivity Research Articles

High-performance proton exchange membrane employing water-insoluble hybrid formed by chemically bonding phosphotungstic acid with polydopamine

Heteropolyacids can retain water in a proton exchange membrane to increase proton conductivity at high temperatures and low humidity; however, their high solubility in water leads to leaching, which limits their further application. Herein, we used phosphotungstic acid (HPW) and polydopamine (PDA) particles to prepare a water-insoluble PDA/HPW hybrid (PDW) via hydrothermal reaction. The amino groups of PDA in PDW chemically bonded to HPW and acted as an anchor for HPW. The proton conductivity of the sulfonated poly(ether ether ketone) (SPEEK) composite membrane containing 15wt% PDW (SPEEK/PDW-15) in liquid water was 0.052 S⸱cm–1 at 25 ℃, which was 63% higher than that of the SPEEK control membrane (0.032 S⸱cm–1). The SPEEK/PDW-15 composite membrane also showed stable proton conductivity during 80 days of testing while immersed in water.

Sulfonated Cobalt Metal-Organic Framework Embedded Mixed Matrix Membrane towards Fuel-Cell Applications.

New strategies for enhancement of the fuel-cell performance of a poly(2,5-benzimidazole) (ABPBI) membrane loaded with a functionalized cobalt-based metal-organic framework (MOF) for H2-O2 fuel cells. ABPBI was prepared using the polycondensation method, and various proportions of sulfonated cobalt MOF (sCo-MOF) were incorporated into ABPBI to fabricate a proton-exchange membrane (PEM). Later, the fabricated membranes were soaked in 1 M sulfuric acid to produce sulfonated PEMs. The developed composite membranes had increased proton conductivity, tensile strength, physicochemical properties, and fuel-cell performance compared to the sulfonated ABPBI (sABPBI) membrane. A membrane embedded with 4 wt % sCo-MOF shows higher water uptake and ion-exchange capacity values of 23.25% and 2.89 mequiv g-1, respectively. The membrane electrode assemblies were fabricated to perform unit-cell tests for both sABPBI and 4 wt % sCo-MOF/sABPBI membranes. The 4 wt % sCo-MOF-loaded sABPBI membrane demonstrated good unit-cell performance in the fuel-cell test, with a power density of 415.8 mW cm-2 at 80 °C, superior to the pristine sABPBI membrane's power density of 178.6 mW cm-2.

Enhanced proton conductivity of sulfonated poly(ether ether ketone) membranes by constructing cation‐π through doping ammonium ionic liquid and graphene oxide

AbstractIn 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.

SYNTHESIS OF POLYMER ELECTROLYTE MEMBRANES BASED ON IONIC LIQUID DOPED SPEEK

The sustainable and environmentally benign energy demand of the world has been increasing. Among the various options, proton exchange membrane fuel cell is an attractive choice for energy supply due to its high efficiency and application conditions without waste. In this research, triazole-based ionic liquid doped sulfonated polyether ether ketone (SPEEK) composite membranes were presented for proton exchange membrane fuel cell (PEMFC) applications. Composite membranes were prepared by incorporating 1,2,3-triazole-based ionic liquids (TIL 1-2-3) into poly(ether ether ketone) (PEEK) matrices. The mechanical, structural, and thermal properties of both composite membranes and the triazole-based ionic liquids were thoroughly characterized using dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The performance and viability of composites for PEMFC applications that involve elevated temperatures were conducted by proton conductivity test across a broad range of temperatures (30-180 oC). High-temperature proton conductivity was measured as 1.73x10-2 S/cm for SPEEK/TIL-3(1.0). According to the proton conductivity test results, it was concluded that the composite membranes may exhibit improved performance in PEMFC applications due to increased proton conductivity values.

Large Scalable High Ion Conductive and Selective Double Layer Membrane Achieved through Dual Ion Conducting Mechanisms

As the share of sustainable energy sources in the electricity supply rises, large-scale energy storage becomes increasingly important. All vanadium flow batteries, as one of the most promising large-scale energy storage methods, have reached the commercialization stage because of their unique feature of uncoupling power and energy, as well as the advantages of long life, high safety, and low cost. The ion-selective membrane is an essential part of flow batteries, which allows specific ions to pass through to maintain a neutral charge and prevents the crossover of active species to maintain the capacity. However, the high cost and low ion-selectivity of the commercialized ion-selective membranes (i.e., Nafion membranes) hindered the further promotion of the flow batteries. Herein, we developed a large scalable double-layer ion selectivity membrane with a unique bifunctional nanoporous boron nitride (PBN) ion selective layer and a low-cost porous polyetherimide (PEI) ion conductivity and support layer. PBN was synthesized by a large scalable template-free method, which was further decorated with Nafion resin. The nano-sized and tortuous pores of the PBN can effectively block the crossover of vanadium ions and provide excellent ion selectivity based on the pore size exclusion mechanism. Furthermore, the super-acidic sulfonic acid groups of Nafion decorated on the nanoporous structure of PBN provide high-speed proton transfer channels that increase proton conductivity through both Grotthuss and vehicle mechanisms. The low-cost porous PEI ion conductivity and support layer was prepared by the phase separation method. The well-aligned asymmetric finger-like porous structure of the PEI membrane provides excellent ion conductivity. The addition of a hydrophilic polymer additive, polyvinylpyrrolidone, further increased its ion conductivity. The PBN–PEI double layer membrane, prepared by a simple spray coating method, demonstrated an excellent ion selectivity (1.49×108 mS cm−3 min), which is almost 15 times higher than that of the pristine PEI membrane (6.71×106 mS cm−3 min) while maintaining high ion conductivity (64 mS cm−1). The PBN–PEI membrane achieved superior performance (97% of coulombic efficiency, 94% of voltage efficiency, and 91% of energy efficiency at 40 mA cm−2) than the Nafion 115 membrane in the all-vanadium flow battery with higher discharge capacity at all current densities and high stability with a lower capacity fading rate (0.17% per cycle vs. 0.74% per cycle at 100 mA cm−2). The PBN–PEI membrane also demonstrated a stable operation in the all-vanadium flow battery at a current density of 100 mA cm−2 over 700 cycles. The work presented the remarkable performance of the ultra-thin PBN bifunctional layer in terms of ion conductivity and selectivity; the combination with the low-cost high ion-conductive porous PEI membrane and a simple fabrication process demonstrated a great potential for commercialization of the PBN-PEI double-layer membrane.

Nanocomposite proton conducting membranes based on sulfonated polystyrene/imidazole‐2‐acetic acid blend for direct methanol fuel cell application

AbstractNanocomposite polyelectrolyte membranes based on sulfonated polystyrene (SPS) /imidazole‐2‐acetic acid (Im) blend (SPSIm), incorporated with halloysite nanotubes (HNTs) were studied for direct methanol fuel cell (DMFC) applications. Firstly, PS was sulfonated at various degrees of sulfonation (DS), and the optimum DS was selected based on hydrolytic stability. Then, SPS was blended with Im as new proton conducting sites. In addition to increasing proton conductivity, methanol permeability decreased due to the attractive interaction between Im and SO3H groups in SPS. In the next step, to introduce tortuous diffusion pathways and hence decrease the methanol crossover, halloysite nanotubes were incorporated into the SPSIm matrix. The results show that the methanol permeability of the membrane incorporated with 1 wt% HNT (SPSIm/HNT) was around 0.527 × 10−7 cm2 s−1, which showed a significant decrease compared to SPS, causing an improvement in the membrane selectivity parameter in comparison to pristine SPS membrane. Furthermore, the thermal properties, ion exchange capacity (IEC), water uptake behavior, and performance of the membranes were evaluated. Based on the results, owing to the reduced methanol permeability, acceptable power density, ease of preparation, as well as low cost, SPSIm/HNT could be considered for DMFC applications.

Application of nanoparticles in modified polybenzimidazole-based high temperature proton exchange membranes

Polymeric proton exchange membranes (PEMs) are vital components of fuel cells, as they enable the transport of protons while preventing the crossover of fuel and oxidant gases. However, conventional PEMs have limitations such as low use temperature, low proton conductivity, and poor mechanical and thermal stability. Various types of nanoparticles have been investigated to modify PEMs to overcome these limitations, as they can increase proton conductivity, mechanical strength, thermal stability, and chemical resistance. Metal oxides such as SiO2 and TiO2 have been shown to improve the proton conductivity and mechanical properties of PEMs. Carbon-based materials such as graphene oxide have been found to enhance both the proton conductivity and thermal stability of PEMs. The use of nanoparticles in modified polymeric PEMs for fuel cells shows excellent potential for improving the performance and durability of fuel cells. Future research should focus on developing cost-effective and scalable methods for nanoparticle synthesis and incorporation into PEMs. Polybenzimidazole (PBI) is the most widely studied high-temperature polymer for preparing composite PEMs. This review provides the recent development of PBI composite PEMs modified with different types of nanoparticles.

New Strategy for Boosting Cathodic Performance of Protonic Ceramic Fuel Cells Through Incorporating a Superior Hydronation Second Phase

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.

Bio-amine crosslinking reforming sulfonated polymer shaped like deoxyribonucleic acid for use in proton exchange membrane fuel cells

This article reports on a study that investigated the use of blended sulfonated polymer membranes for fuel cell applications. The researchers blended a sulfonated poly(arylene ether) polymer material with an amine-based crosslinking agent in 1%–5% varying weight percentages. By replacing the sulfonates' hydrogen bonds with the amine groups in the crosslinking agent, the researchers were able to enhance the structure of the polymer material. This, in turn, can help resolve the issue of inadequate dimensional stability of SA8, thereby prolonging the lifespan of fuel cells. The resulting membranes showed improved dimensional stability, oxidative stability, and cell component efficiency, with the 5% crosslinking agent blend ratio demonstrating decrease 30.8 times in swelling ratio and a 4.9% increase in oxidative stability. Additionally, the fuel cell efficiency of the 1% crosslinking agent blend ratio membrane was 20.4% higher than that of the commercial membrane, with a power density of 1.21 W/cm2. The SA8+1P blend ratio had the highest ion exchange capacity and water uptake, resulting in increased proton conductivity and power density. Furthermore, the dimensional stability of the membranes improved with the blend ratio, with the SA8+5P membrane outperforming the commercial Nafion 211 membrane. The SA8+1P and SA8+5P membranes have been proven to demonstrate exceptional performance in terms of ion exchange capacity, conductivity, and dimensional stability. Furthermore, these membranes also show high efficiency in fuel cell efficiency. Overall, the results suggest that blending sulfonated polymer membranes with an amine-based crosslinking agent has the potential to improve the performance of fuel cell components.

Polybenzimidazole Membranes as Nafion Replacement in Aqueous HCl Electrolyzers

We demonstrate the use of para-polybenzimidazole (PBI) membranes as replacements for Nafion membranes in aqueous HCl oxygen-depolarized electrolyzers. Both para-PBI and densified para-PBI membranes reduce the cell voltage needed at 0.5 A cm–2 by ≥100 mV. We examine the effect of HCl(aq) flow rate, back-pressure, electrolyzer temperature, and, for the densified para-PBI membranes, H3PO4 swell time on electrolyzer performance. Increased proton conductivity, measured as reduced area-specific membrane resistance, is identified as the primary mechanism to explain the improved performance of the electrolyzer.

Sulfonated graphene oxide/sulfonated poly (2,6‐ dimethyl – 1,4‐phenylene oxide) as a potential proton exchange membrane for iron air flow battery application

AbstractA series of proton exchange membranes (PEMs) of sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) with different sulfonated graphene oxide (SGO) (0, 0.25, 0.5, 0.75, 1.0, 1.5%) were prepared for possible application in Iron‐air/flow battery. The presence of SGO in the membrane improved the water uptake of all membranes prepared and decreased the swelling ratio. The SPPO/1% w/w SGO showed good properties with higher water uptake of 44.1%, water retention of 42.48% and swelling ratio of 21.4% at 25°C. However, the 0.75% SGO exhibited the highest proton conductivity of 0.98 S/cm and better dispersion, elemental distribution, and morphology. In addition, SGO improved the thermal stability of all composite membranes. The chemical stability of all membranes remained good after 7 days in a 1 M HCL solution. The SPPO/0.75%w/w SGO showed increased proton conductivity when degradation properties were evaluated. Compared to Nafion 117, all composites showed lower iron crossover. Nafion had a high permeability of 3.03 × 10−7 cm−2/s, which is 75% higher than the 7.6 × 10−8 cm−2/s of SPPO/SGO‐1.5% and 52% higher than the 1.46 × 10−7 cm−2/s of SPPO/SGO‐0.75%. The results indicate that SGO is a good inorganic filler for the composite proton exchange membrane and stable enough for possible application in an iron‐air/flow battery.

Investigating the Performance of a Zinc Oxide Impregnated Polyvinyl Alcohol-Based Low-Cost Cation Exchange Membrane in Microbial Fuel Cells.

The current study investigated the development and application of lithium (Li)-doped zinc oxide (ZnO)-impregnated polyvinyl alcohol (PVA) proton exchange membrane separator in a single chambered microbial fuel cell (MFC). Physiochemical analysis was performed via FT-IR, XRD, TEM, and AC impedance analysis to characterize thus synthesized Li-doped ZnO. PVA-ZnO-Li with 2.0% Li incorporation showed higher power generation in MFC. Using coulombic efficiency and current density, the impact of oxygen crossing on the membrane cathode assembly (MCA) area was evaluated. Different amounts of Li were incorporated into the membrane to optimize its electrochemical behavior and to increase proton conductivity while reducing biofouling. When acetate wastewater was treated in MFC using a PVA-ZnO-Li-based MCA, the maximum power density of 6.3 W/m3 was achieved. These observations strongly support our hypothesis that PVA-ZnO-Li can be an efficient and affordable separator for MFC.

A simple MOF constructed using Pb(II) with strong polarizing force: a filler of Nafion membrane to increase proton conductivity.

Metal-organic frameworks (MOFs) are promising competitive candidates as fillers for Nafion proton exchange membrane (PEM). Increasing efforts have been made to explore methods for synthesizing MOF fillers and the mechanism by which MOF doping improves the proton conductivity (σH+) values of composite membranes. In this study, a Pb(II) cation with strong polarizing force was selected for the hydrothermal reaction with a simple sulfoterephthalate ligand (H3L). Pb-MOF [Pb2L(OH)]n was obtained, which was constructed using Pb-O layers and deprotonated sulfoterephthalate L3- and exhibited good thermal and water stability. Different amounts of Pb-MOF particles were doped into Nafion to fabricate Pb-MOF/Nafion-x composite membranes, which were characterized using SEM, PXRD, IR spectroscopy, TGA, and other methods. It was found that doping Pb-MOF can apparently improve the water absorbability and thermal stability of the composite membrane. The σH+ of the Pb-MOF/Nafion-7 composite membrane was the highest and 2.14 times that of the pure Nafion membrane at 353 K. The higher proton conduction properties may be explained by the strong polarization force, and Pb(II) cations on the surface of Pb-MOF can decrease the bond energy of the O-H bond of absorbed water molecules and increase the acidity of the composite membrane. The phenomena in this study and our previous study confirm that acidity is the most important factor in favor of proton conductivity.

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.

Proton conductivity and dimensional stability of proton exchange membrane: A dilemma solved by chitosan aerogel framework

Increasing proton conductivity of polymer electrolyte membrane (PEM) by introducing more number of proton transfer species, especially sulfonated groups always lead to a decrease in mechanical/dimensional stability. The present work proposes the solution to overcome this dilemma by applying chitosan (CS) interconnected with sulfonated poly(ether ether ketone) (SPEEK) to provide not only the 3D framework for dimensional stability but also the sulfonated groups and amino groups play the role in proton transfer. By simply crosslinking CS with succinic acid (SA) followed by lyophilizing, the stable 3D-framework (CS-x)-SA can be obtained. This (CS-x)-SA framework allows the incorporation of SPEEK during membrane formation results in semi-interpenetrating (CS-x)-SA-SPEEK. The (CS-0.25)-SA-SPEEK membrane obtained performs mechanical stability in terms of tensile strength for 12%, with a proton conductivity increment for 34% as compared to SPEEK. The present work demonstrates an approach to achieve the 3D interconnected composite PEM to achieve the improvement in proton transfer efficiency and mechanical strength as well as dimensional stability.

Activating Nitrogen‐doped Graphene Oxygen Reduction Electrocatalysts in Acidic Electrolytes using Hydrophobic Cavities and Proton‐conductive Particles

AbstractAlthough pyridinic‐nitrogen (pyri‐N) doped graphene is highly active for the oxygen reduction reaction (ORR) of fuel cells in alkaline media, the activity critically decreases under acidic conditions. We report on how to prevent the deactivation based on the mechanistic understanding that governs the ORR kinetics. First, we considered that the deactivation is due to the hydration of pyri‐NH+, leading to a lower shift of the redox potential. Introducing the hydrophobic cavity prevented the hydration of pyri‐NH+ but inhibited the proton transport. We then increased proton conductivity in the hydrophobic cavity by introducing SiO2 particles coated with ionic liquid polymer/Nafion® which kept the high onset potentials with an increased current density even in acidic media.

Activating Nitrogen-doped Graphene Oxygen Reduction Electrocatalysts in Acidic Electrolytes using Hydrophobic Cavities and Proton-conductive Particles.

Although pyridinic-nitrogen (pyri-N) doped graphene is highly active for the oxygen reduction reaction (ORR) of fuel cells in alkaline media, the activity critically decreases under acidic conditions. We report on how to prevent the deactivation based on the mechanistic understanding that governs the ORR kinetics. First, we considered that the deactivation is due to the hydration of pyri-NH+ , leading to a lower shift of the redox potential. Introducing the hydrophobic cavity prevented the hydration of pyri-NH+ but inhibited the proton transport. We then increased proton conductivity in the hydrophobic cavity by introducing SiO2 particles coated with ionic liquid polymer/Nafion® which kept the high onset potentials with an increased current density even in acidic media.

A novel strategy toward the advancement of proton exchange membranes through the incorporation of propylsulfonic acid-functionalized graphene oxide in crosslinked acid-base polymer blends

Propylsulfonic acid-functionalized graphene oxide (PrSGO) was introduced into the sulfonated poly(ether ether ketone) (SPEEK)-sulfonated poly(benzimidazole) (SPBI) blend in this study to understand the impact on glass transition temperature (Tg), structural properties, increase mechanical properties, proton conductivity, and single-cell performance. At different loadings of PrSGO, atomistic molecular dynamics (MD) simulations of SPEEK/SPBI, cross-linked SPEEK/SPBI (XSPEEK/SPBI), and XSPEEK/SPBI/PrSGO composite systems were performed. Tg was increased after cross-linking the polymer systems and increasing the loading percent of PrSGO filler and SPBI in the polymer systems. The mechanical properties, chemical and thermal stability of the XSPEEK/SPBI/PrSGO nanocomposite membranes significantly increased PrSGO loading because of the strong interfacial interaction between PrSGO and the XSPEEK/SPBI matrix. XSPEEK/SPBI/PrSGO nanocomposite membrane at 4 wt % PrSGO loading demonstrated a considerable improvement in proton conductivity up to 0.17 S/cm at 100% relative humidity (RH) at 90 °C. Furthermore, the XSPEEK/SPBI/PrSGO nanocomposite membrane at 4 wt% PrSGO loading demonstrated good fuel cell (FC) performance with a maximum power density of ∼0.82 W/cm2 at 100% RH, 80 °C. Incorporating PrSGO nanofillers in the polymer matrix considerably improved proton conductivity of the membranes, other significant properties, and overall FC performance due to their hygroscopic nature, a higher number of sulfonic acid groups, and excellent interaction of the acid functionalized fillers with the cross-linked SPEEK/SPBI-based matrix.

Dual-sulfonated MOF/polysulfone composite membranes boosting performance for proton exchange membrane fuel cells

Nafion is the most widely used polymer electrolyte membrane (PEM) owing to its excellent physical stability and superior proton conductivity in the presence of long-side-chain perfluorinated sulfonic acid. However, commercially available Nafion is very expensive, limiting its practical application. Thus, a new proton exchange membrane must be developed to replace conventional Nafion for practical electrochemical system operations. In this study, we rationally designed dual-sulfonated polysulfone (PSF)/metal–organic framework (MOF) composite membranes for use as PEMs. Sulfonated PSF (sPSF) was systematically prepared with a controllable sulfonation degree. Additionally, sulfonated MOFs (sMOF; MIL-101(Cr)-SO3H and UiO-66(Zr)-SO3H) were incorporated into the sPSF matrix to form dual-sulfonated PSF/MOF composite membranes. The sMOF offers a high Brunauer-Emmett-Teller (BET) surface area with sulfonated sites that can effectively control water molecules and ion transport, increasing proton conductivity and dimensional stability. With an optimal MOF loading (∼3 wt%), the sPSF/sMOF composite membranes exhibited a high proton conductivity (∼0.18 S/cm) at room temperature under fully humid conditions. Additionally, the sPSF/sMOF composite membranes showed a moderate swelling ratio owing to the high dimensional stability due to the adsorbed molecules in the MOF framework. Particularly, the sPSF/sMOF composite membranes also exhibited a high proton conductivity at high temperatures (∼75 °C) and moderate relative humidity (∼60–80 % RH), demonstrating their high potential for practical operation. Thus, the sPSF/sMOF composite membranes show good potential as a novel PEM for electrochemical applications.

Self-assembled proton conduction networks consisting of SPEEK, NH2-POSS, and IL with enhanced proton conduction and decreased IL loss

To enhance the conductivity of sulfonated polyether ether ketone (SPEEK, SP) membrane and avoid the loss of ionic liquid (IL), using aminopropyloligosisiloxane (NH 2 -POSS) as molecular hybrid filler, a self-assembled medium temperature and non-humidified SP/IL/NH 2 -POSS hybrid membrane was prepared. NH 2 -POSS can be assembled into the hydrophilic domain ion phase of SPEEK. In which, –NH 2 of NH 2 -POSS and –SO 3 H of SPEEK formed acid-base pairs at the interface which were conducive to the construction of proton transport channel. In addition, NH 2 -POSS enriched IL in the hydrophilic domain, which retained IL while synergistically increased the conductivity. The results showed that the IL loss rate of SP/IL/NH 2 -POSS-2 membrane was 46.9 wt%, which was about 55.8% of SP/IL membrane; the conductivity of SP/IL/NH 2 -POSS-2 membrane at 200 °C without humidification was 5.51 mS·cm −1 , which was about 4 times that of SP/IL membrane. • Molecular-level network SP/IL/NH 2 -POSS proton exchange membrane was prepared. • -NH 2 and –SO 3 H constructed ordered proton transport channels via acid-base pairs. • IL is enriched on NH 2 -POSS and SPEEK interface through hydrogen bonding. • Acid-base pairs and IL-rich layer synergistically increase proton conductivity.