Proton Conductivity Of Hybrid Membranes Research Articles

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 new alternative transmission sites by incorporating structure-defect metal-organic framework into sulfonated poly(arylene ether ketone sulfone)s

Metal-organic frameworks are new kinds of porous crystalline materials. The Zr-based metal-organic framework (MOF-801) is consists of [Zr6(u3-O)4(u3-OH)4]12+ clusters and fumaric acid connectors. MOF-801 has excellent mechanical properties, high chemical stability and high water absorption capacity. There are a large number of hydrophilic functional groups inside MOF-801, which is effective to promote interfacial compatibility between MOF-801 and polymer matrixes. In this work, the MOF-801 with structural defects was synthesized through the solvothermal method by adding excess formic acids as the regulator. These structural defects could confer MOF-801 high surface area (2476.34 m2 g−1) and promote the water absorption capacity. Moreover, structural defects could also expose more open metal sites of MOF-801, thereby increasing the Lewis acidity of MOF-801. Then, the hybrid membranes were synthesized by combining the MOF-801 with structural defects and C-SPAEKS. Dense hydrogen-bond networks formed between the MOF-801 and C-SPAEKS further promote enhance proton conductivity. At the condition of 90 °C and 100% relative humidity, the highest proton conductivity of hybrid membranes reached 0.100 S cm−1, which is similar to that of Nafion 117. Meanwhile, these hybrid membranes showed outstanding chemical and thermal stabilities. These results indicate that these hybrid membranes have potential as proton exchange membranes.

Proton Conductive Membranes from Covalently Cross‐Linked Poly(Acrylate)/Silica Interpenetrating Networks

AbstractThe preparation of hybrid proton conductive membranes that comprise of covalently linked interpenetrating polymer and inorganic networks is reported. The hybrid membranes are synthesized via simultaneous photo‐initiated polymerization and sol–gel processing. The simultaneous processing permeates fabrication of the membranes that comprises covalently cross‐linked polymeric and inorganic networks. The membranes are characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy, scaning electron microsopy, thermogravimetric analysis, differential scanning calorimetry, in order to confirm their chemical composition, structure, and morphology. An addition of 3‐methacryloxypropyl trimethoxysilane into the sol–gel composition allows the formation of covalent linkages between polymeric and inorganic networks, which facilitates a uniform distribution of the molecular components across the fabricated membranes. The incorporation of the silica network leads to an increase in water retention and proton conductivity of hybrid membranes as compared to their purely polymeric analogues.

Proton Conduction of Nafion Hybrid Membranes Promoted by NH3-Modified Zn-MOF with Host–Guest Collaborative Hydrogen Bonds for H2/O2 Fuel Cell Applications

It is of great significance to develop creative proton exchange membrane materials for proton exchange membrane fuel cells (PEMFCs). The strategy of doping metal-organic frameworks (MOFs) with guest molecules into the Nafion matrix is adopted to improve the electrochemical performance of Nafion hybrid membranes. Various and abundant hydrogen bonds can make a tremendous contribution to the proton conduction of hybrid membranes. In this work, we used high proton-conducting Zn-MOFs with the characteristics of host-guest collaborative hydrogen bonds as the filler to prepare Zn-MOF/Nafion hybrid membranes. Alternating current (AC) impedance tests show that when the doping amount of Zn-MOF is 5%, the proton conductivity reaches 7.29 × 10-3 S·cm-1, being 1.87 times that of the pure Nafion membrane at 58% relative humidity (RH) and 80 °C. In an attempt to prove the promotion effect of guest NH3 on proton conductivity of Nafion hybrid membranes, Zn-MOF-NH3 was filled into the Nafion matrix. Under the same conditions, its proton conductivity reaches the maximum value of 2.13 × 10-2 S·cm-1, which is 5.47 times that of the pure Nafion membrane. Zn-MOF-NH3/Nafion-5 was used to fabricate a proton exchange membrane for application in H2/O2 fuel cells. The maximum power density of 212 mW cm-2 and a current density of 630 mA cm-2 reveal a respectable single cell performance. This study provides a promising method for optimizing the structure of MOF proton conductors and inspires the preparation of high-performance Nafion hybrid membranes.

Dual-functional coordination polymers with high proton conduction behaviour and good luminescence properties.

Two coordination polymers, [M(5-hip)(H2O)3]n (M = Cd2+ (1), Zn2+ (2), 5-hip = 5-hydroxyisophthalic acid), have been synthesized under hydrothermal conditions. The crystal structure reveals that complexes 1 and 2 have 1D chain structures by the coordination of metal ions and 5-hip. 1D chains are connected by hydrogen bonds to form a 3D structure. AC impedance analysis shows that the proton conductivity of complexes 1 and 2 comes up to 1.58 × 10-3 S cm-1 (98%RH, 343 K) and 5.27 × 10-4 S cm-1 (98%RH, 353 K), respectively. To further improve the proton conductivity, a hybrid membrane was prepared by the solution casting method with complexes as fillers and sulfonated polyether ether ketone (SPEEK) as the organic matrix. The proton conductivity of hybrid membranes 1@SPEEK-5 and 2@SPEEK-5 is 1.97 and 1.58 times higher than that of pure SPEEK membranes, respectively. Furthermore, the two complexes are excellent fluorescent sensors, which could detect Cr2O72- in aqueous solution with high sensitivity and selectivity. Both of them have low detection limits for Cr2O72- in aqueous solution, where the detection limit of complex 1 is 0.8 μM and that of complex 2 is 1 μM. The above work demonstrates that the two complexes are dual-functional materials with high proton conduction and good fluorescence properties.

Information Technology in Development of Solid Polymer Electrolyte Fuel Cells

The proton-conducting hybrid organic-inorganic composites based on tetraethoxysilane and sulfonated styrene (St) and allyl glycidyl ether (AGE) copolymers, which are characterized by high exchange capacity and specific conductivity, are formed by sol-gel synthesis. The results of a quantum-chemical calculations of the geometry of the structure of an organic-inorganic composite (for a model consisting of 78 atoms) allow us to associate an increase in the proton conductivity of hybrid membranes, compared with the initial copolymer, with the generation of crystallization water and free sulfuric acid during the formation of the composite.

Long-term durable solid state electrolyte membranes based on a metal–organic framework with phosphotungstic acid confined in the mesoporous cages

In this study, phosphotungstic acid-encapsulated MIL-101 (Fe) (HPW@MIL-100 (Fe)) was synthesized by the in-situ direct hydrothermal method. Due to the large mesoporous cages and small microporous windows of MIL-100 (Fe), HPW could be well loaded and confined in the cages of MIL-100 (Fe). Furthermore, novel hybrid proton exchange membranes were fabricated by incorporating HPW@MIL-100 (Fe) into sulfonated poly (arylene ether ketone sulfone) containing carboxyl groups (C-SPAEKS) matrix. The structures of MIL-100 (Fe), HPW@MIL-100 (Fe), C-SPAEKS, and hybrid membranes were characterized by XRD and FT-IR. The HPW@MIL-100 (Fe), with a large amount of phosphotungstic acid in cages, could enhance the proton conductivities of hybrid membranes. The hybrid membrane with 4% content of HPW@MIL-100 (Fe) achieved a high proton conductivity of 0.072 S cm−1 at 80 °C and 100% relative humidity, which was 1.8 times higher than that of pure C-SPAEKS (0.040 S cm−1) at the same conditions. Meanwhile, the introduced HPW@MIL-100 (Fe) fillers improved the dimensional stability of hybrid membranes. These results indicate that introduction of MIL-100 (Fe) materials loaded with HPW plays an important role in improving the comprehensive performance and this series of hybrid membranes have potential as proton exchange membranes.

Preparation of a Cross-Linked Sulfonated Poly(arylene ether ketone) Proton Exchange Membrane with Enhanced Proton Conductivity and Methanol Resistance by Introducing an Ionic Liquid-Impregnated Metal Organic Framework.

A novel ionic liquid-impregnated metal-organic-framework (IL@NH2-MIL-101) was prepared and introduced into sulfonated poly(arylene ether ketone) with pendent carboxyl groups (SPAEK) as the nanofiller for achieving hybrid proton exchange membranes. The nanofiller was anchored in the polymeric matrix by the formation of amido linkage between the pendent carboxyl group attached to the molecule chain of SPAEK and amino group belonging to the inorganic framework, thus leading to the enhancement in mechanical properties and dimensional stability. Besides, the hybrid membrane (IL@MOF-1) exhibits an enhanced proton conductivity up to 0.184 S·cm-1 because of the incorporation of ionic liquid in the nanocages of NH2-MIL-101. Moreover, the special structure of NH2-MIL-101 contributes to a low leakage of ionic liquid so as to retain the stable proton conductivity of hybrid membranes under fully hydrated conditions. Furthermore, as a result of a cross-linked structure formed by inorganic nanofiller, the IL@MOF-1 hybrid membrane shows a lower methanol permeability (7.53 × 10-7 cm2 s-1) and superior selectivity (2.44 × 105 S s cm-3) than the pristine SPAEK membrane. Especially, IL@MOF-1 performs high single-cell efficiency with a peak power density of 37.5 mW cm-2, almost 2.3-fold to SPAEK. Electrochemical impedance spectroscopy and scanning electron microscopy indicated that the nanofiller not only contributed to faster proton transfer but also resulted in a tighter bond between the membrane and catalyst. Therefore, the incorporation of IL@NH2-MIL-101 to prepare the hybrid membrane is proven to be suitable for application in direct methanol fuel cells.

Proton conductivity of hybrid membranes based on polybenzimidazoles and surface-sulfonated silica

Hybrid membranes based on polybenzimidazole PBI-O-PhT (a polymer based on 3,3′,4,4′‑tetraaminodiphenyl oxide and 3,3‑bis(p‑carboxyphenyl)phthalide) were obtained by casting with silica particles with the surface modified by sulfonic groups. The morphology, thermal stability, proton conductivity under various conditions, and hydrogen permeability of the obtained membranes were investigated. It was shown that modification with small amounts of silica (2–5%) increases the conductivity and practically has no influence on the gas permeability of the hybrid membranes.

Synergy between Isomorphous Acid and Basic Metal-Organic Frameworks for Anhydrous Proton Conduction of Low-Cost Hybrid Membranes at High Temperatures.

Metal-organic frameworks (MOFs) embedded in polymer have showed efficiency in improving proton conduction of hybrid membranes under hydrated conditions. However, anhydrous proton conduction of such hybrid membranes over 100 °C remains great challenge. Here, proton conductive hybrid membranes combined acid group (-SO3H)- and basic group (-NH2)-modified isomorphous MOFs, namely UiO-66(SO3H) (abbreviated as A, the initial of acid) and UiO-66(NH2) (abbreviated as B, the initial of basic) and a low-cost polymer (chitosan, CS) were prepared. The proton conductivity of the optimum dual MOF-cofilled hybrid membranes (CS/A + B) reached 3.78 × 10-3 S/cm at 120 °C and under anhydrous conditions, under which each component, that is MOF A, MOF B and CS, and single MOF-filled hybrid membranes (CS/A and CS/B) nearly lost proton conduction without exception, producing unprecedented results of one plus one more greater than two. The synergistic effects among UiO-66(SO3H), UiO-66(NH2), and CS on improving conductivity are also observed under hydrated conditions, the highest proton conductivity of CS/A + B reached 5.2 × 10-2 S/cm, which is 1.86, compared to that of the pure CS membrane at 100 °C and 98% relative humidity. The anhydrous proton conductivity of CS/A + B over 100 °C is one of the highest for MOF-based hybrid membranes. MOFs and hybrid membranes were extensively characterized and the proton conductive mechanism was revealed. The achievements open a new avenue for MOF-based anhydrous proton-conducting membranes and would advance the exploration of future application of these MOFs in fuel cells.

Nafion- and aquivion-based nanocomposites containing detonation nanodiamonds

Nafion- and Aquivion-based composite solid polyelectrolytes containing deagglomerated detonation nanodiamonds were studied by the impedance spectroscopy method. It was found that introduction of these dopants leads to a substantial increase in proton conductivity of hybrid membranes with low relative humidity.

Enhanced proton conductivity of proton exchange membranes by incorporating phosphorylated hollow titania spheres

The synergistic enhancement in proton conductivity of hybrid membranes by improving the water retention capacity and introducing additional proton transfer sites is reported.

Sulfonic acid-functionalized hybrid organic–inorganic proton exchange membranes synthesized by sol–gel using 3-mercaptopropyl trimethoxysilane (MPTMS)

Organic/inorganic hybrid membranes based on (3-glycidoxypropyl) trimethoxysilane (GPTMS) and 3-mercaptopropyl trimethoxysilane (MPTMS) have been prepared by sol–gel method and organic polymerisation, as candidate materials for proton exchange membranes in direct alcohol fuel cell (DMFC) applications. The –SH groups of MPTMS are oxidized to sulfonic acid groups, which are attributed to enhance the proton conductivity of hybrid membranes. FTIR, XPS and contact angle were used to characterize and confirm the hybrid structure and oxidation reaction progress. Membranes characterization also includes ion exchange capacity, water uptake, methanol permeability and proton conductivity to confirm their applicability in fuel cells. All the membranes were homogeneous and thermally and chemically resistant. In particular, the hybrid membranes demonstrated proton conductivities as high as 0.16 S cm−1 at high temperature, while exhibiting a low methanol permeability as compared to Nafion®. These results are associated with proton conducting paths through the silica pseudo-PEO network in which sulfonic acid groups work as proton donor.

Sulfonic Acid-Functionalized Hybrid Proton Exchange Membranes Synthesized By Sol-Gel for Direct Methanol Fuel Cells

Organic/inorganic hybrid membranes based on (3-glycidoxypropyl) trimethoxysilane (GPTMS) and 3-mercaptopropyl trimethoxysilkane (MPTMS) have been prepared by sol-gel method and organic polymerisation, as candidate materials for proton exchange membranes in direct alcohol fuel cell (DMFC) applications. The –SH groups of MPTMS are oxidized to sulfonic acid groups, which are attributed to enhance the proton conductivity of hybrid membranes. FTIR, Raman and XPS were used to characterize and confirm the hybrid structure and oxidation reaction progress. Membranes characterization includes ion exchange capacity, water uptake, methanol permeability and proton conductivity to confirm their applicability in fuel cells. All the membranes were homogeneous thermally and chemically strong. In particular, our hybrid membranes demonstrated proton conductivities as high as 0.03 S/cm, at high temperature, while exhibiting high methanol permeability as compared to Nafion®. These results show that this kind of hybrid membranes possess high proton conductivity and a high barrier to methanol permeation due to the proton conducting path through the silica pseudo-PEO network in which sulfonic acid groups work as proton donor. Collectively, our results indicate that crosslinked MPTMS-GPTMS oxidized hybrid membranes offer great potential for use as PEMs in DMFC applications.

Synthesis and characterization of high temperature proton exchange membrane from isocyanatopropyltriethoxysilane and hydroxyethane diphosphonic acid

High temperature proton exchange membranes with phosphonic acid functionalization were prepared from 3-Isocyanatopropyltriethoxysilane (IPTES), 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) and Tetraethoxysilane (TEOS) by sol–gel process. These hybrid membranes with different amount of phosphonic acid were investigated with respect to structure, thermal property, proton conductivity and hydrogen bond network. The results of FT-IR and 13C NMR reveal that HEDPA is chemically bound to siloxane network as a result of reaction between the OH group of HEDPA and the isocyanate group of IPTES. XRD patterns of the hybrid membranes show the membranes are amorphous. Thermal analysis including TG and DSC confirm that the hybrid membranes are thermally stability up to at least 225 °C. The proton conductivity of hybrid membrane with the molar ratio of IPTES/TEOS/HEDPA = 1/0.5/0.8 is 4.6 × 10−2 S cm−1 and 2.36 × 10−2 S cm−1 at 100 ％ relative humidity and under anhydrous condition, respectively, at 160 °C. 1H NMR and Variable-temperature FT-IR analysis demonstrate that there is complex hydrogen bond network within hybrid membranes among P–OH, CO, PO and N–H.

Enhanced proton conductivity of hybrid membranes by incorporating phosphorylated hollow mesoporous silica submicrospheres

Hollow mesoporous silica submicrospheres (HMSS) are prepared with one-dimensional hexahedral mesopores regularly aligned along the radial directions of the silica shells. Both the outer and the inner surfaces of the mesoporous shells, as well as the mesopore walls are phosphorylated (PHMSS). Moreover, the lumen of PHMSS serves as accommodation for amino tris(methylene phosphonic acid) (ATMP) with large amount of phosphoric acid groups. Phosphorylated submicrospheres (PHMSS-ATMP) with multi-functionalities are thus prepared. After incorporating PHMSS-ATMP into chitosan (CS) matrix, the hybrid membranes were fabricated. The water uptake, anti-swelling properties and the proton conductivities are all enhanced. Particularly, the proton conductivities are considerably elevated and the highest proton conductivity is 9.4×10−2Scm−1 at 110°C 100% RH for the membrane with 7.5wt% of PHMSS-ATMP; the proton conductivities of CS/PHMSS-ATMP hybrid membranes at 80°C and low humidity are increased by two orders of magnitude compared to the pristine CS membrane. The enhanced performance could be attributed to the proton conducting groups introduced by PHMSS-ATMP: –PO3H2 groups are anchored on the surface of PHMSS-ATMP, and proton conducting channels could be formed by the mesopores of the silica shell, and the lumen could serve as acidic reservoirs.

Designing Hybrid Inorganic-Organic Materials By Utilizing Sol-Gel Chemistry for Batteries and Energy Storage

The focus of this work is to investigate the morphology, physical properties, and ion transport of tetraethyl orthosilicate (TEOS)-titanium isopropoxide (TIP)-polymer hybrid membranes depending on different composition. TEOS and TIP are two precursors used in sol-gel process to prepare Si-Ti mixed materials as the inorganic component. Penta block copolymer (PBC) is used as the organic component, which is poly(t-butyl styrene-b-ethylene-co-propylene-b-styrene-co-styrenesulfonate-b-ethylene-co-propylene-b-t-butyl styrene). Unlike the previous work done by soaking membrane in inorganic sol or mixing polymer with inorganic particles, TEOS-TIP-PBC hybrid membranes were prepared from homogenous inorganic-organic solutions by controlling different TEOS: TIP molar ratio and different concentration of inorganic components in hybrid membranes. Contact angle data by Kruss DSA 100 surface analyser, water uptake, proton conductivity by Autolab potentiostat, mechanical properties by dynamic mechanical analysis (DMA), and thermal stability by thermal gravity analysis (TGA) were investigated and highly affected by the composition. The most interesting results we found is that the proton conductivity of hybrid membranes with both acid and salt form was significantly increased compared with the pure PBC membranes, which opens the potential that these novel hybrid materials can be used in fuel cells, lithium-ion battery, or vanadium redox flow battery. In the future work, other polymers with sulfonate group, such as Nafion, will be included to prepare hybrid membranes. Moreover, other characterizations and applications, such as transmission electron microscopy (TEM), small angle x-ray scattering (SAXS), methanol permeability, and single cell performance of these hybrid membranes will be further investigated.

TEOS-TIP-PBC Hybrid Inorganic-Organic Membranes for Batteries and Energy Storage

The focus of this work is to investigate the morphology, physical properties, and ion transport of Tetraethyl orthosilicate (TEOS)-Titanium isopropoxide (TIP)-Penta block copolymer (PBC) hybrid membranes depending on different composition. TEOS and TIP are two precursors used in sol-gel process to prepare Si-Ti mixed materials as the inorganic component. PBC is poly(t-butyl styrene-b-ethylene-co-propylene-b-styrene-co-styrenesulfonate-b-ethylene-co-propylene-b-t-butyl styrene) as the organic component. Unlike the previous work done by soaking membrane in inorganic sol or mixing polymer with inorganic particles, TEOS-TIP-PBC hybrid membranes were prepared from homogenous inorganic-organic solutions by controlling different TEOS: TIP molar ratio and different concentration of inorganic components in hybrid materials. Contact angle data by Kruss DSA 100 surface analyser, water uptake, proton conductivity by Autolab potentiostat, mechanical properties by dynamic mechanical analysis (DMA), and thermal stability by thermal gravity analysis (TGA) were investigated and highly affected by the composition. The most interesting results we found is that the proton conductivity of hybrid membranes with both acid and salt form was significantly increased compared with the pure PBC membranes, which opens the potential that these novel hybrid materials can be used in fuel cells, lithium-ion battery, or vanadium redox flow battery. In the future work, other polymers with sulfonate groups, such as Nafion, will be included to prepare hybrid membranes. Moreover, other characterizations and applications, such as transmission electron microscopy (TEM), small angle x-ray scattering (SAXS), methanol permeability, and single cell performance of these hybrid membranes will be further investigated.

Impregnation of imidazole functionalized polyhedral oligomeric silsesquioxane in polymer electrolyte membrane for elevated temperature fuel cells

Imidazole functionalized polyhedral oligomeric silsesquioxane (ImPOSS) is synthesized and introduced into a polymer electrolyte membrane for elevated temperature applications. Aggregates of ImPOSS containing 30–40 blocks of POSS cages are observed. The synthesized ImPOSS are well distributed in the hybrid membrane without further aggregation during the membrane formation process. The resulting hybrid membrane exhibits strong Coulombic interaction between sulfonic acid groups on Nafion and imidazole moieties on ImPOSS, leading to increased glass transition temperature and improved thermal stability of the membranes. Under anhydrous conditions, Vogel–Tamman–Fulcher type temperature-dependent proton conductivity is observed, suggesting that structural reorganization of incorporated imidazole moieties dominates the long-range proton transfer in the hybrid membrane. The anhydrous proton conductivity of hybrid membranes containing 35 wt% of ImPOSS reaches 0.0256 S cm−1 at 140 °C. The output voltage of a single cell assembled from the hybrid membrane is observed to be 0.41 V at 600 mA cm−2 under 120 °C and 25% relative humidity using hydrogen and oxygen as reaction gases. The results show the potential applicability of ImPOSS-Nafion hybrid membranes for elevated polymer electrolyte membrane fuel cells.

Influence of sol–gel media on the properties of Nafion–SiO2 hybrid electrolytes for high performance proton exchange membrane fuel cells operating at high temperature and low humidity

The effects of alcohol used as solvent during the sol–gel synthesis of Nafion–SiO2 hybrid electrolytes have been evaluated. The alcohol controls the distribution of silica particles in the phase separated structure of Nafion and both the silica content and the water uptake of hybrid membranes are dependent on the alcohol solvent. Thermal and structural properties inferred from differential scanning calorimetry and small angle X-ray scattering were correlated with the enhanced water uptake and the proton conductivity of hybrid membranes. Accordingly, fuel cell tests carried out at 130°C and low humidity evidenced the superior performance of Nafion–SiO2 hybrids.