Organic Inorganic Hybrid Proton Exchange Membranes Research Articles

Enhancing proton conductivity and methanol resistance of SPAEK membrane by incorporating MOF with flexible alkyl sulfonic acid for DMFC

Metal-organic frameworks (MOFs)-doped hybrid SPAEK-based proton exchange membranes (PEMs) can combine the advantages of both to promote the comprehensive performance of hybrid membranes. However, the complicated preparation process and low yield of functionalized MOF restricted their application in organic-inorganic hybrid PEMs. Herein, an amino-sulfonic acid-based bi-functionalized MOF (MNCS), containing flexible sulfonic acid chains, was prepared by an uncomplicated and efficient one-step modification method. The sulfonic acid groups on MNCS were grafted to the end of flexible side chains with large free volume, which facilitated the formation of broad and continuous proton transport channels to reduce the activation energy of proton transport. Meanwhile, the amino groups of MNCS establish a second proton transport channel with the sulfonic acid groups in SPAEK due to acid-base pair interactions. Furthermore, owing to the formation of the ionic cross-linking structure, the dimensional stability and methanol resistance of MNCS@SNF-PAEK were significantly improved. Especially, MNCS@SNF-PAEK-1.5 showed the highest proton conductivity of 0.188 S cm−1,endowing it with a maximum power density of 90.8 mW cm−2 in direct methanol fuel cell (DMFC), which substantially exceeded that of pristine SNF-PAEK membrane. It illustrated that the hybrid membranes by incorporating MNCS showed promising potential in DMFC.

Organic-inorganic (polysiloxane) crosslinked sulphonated poly(ether ether ketone ketone) hybrid membranes for direct methanol fuel cells

A series of Ph-m-SPEEKK/polysiloxanes organic-inorganic hybrid proton exchange membranes (HMs) were prepared. The Ph-m-SPEEKK was synthesized from 2-phenylhydroquinone and 1,3-bis(4-fluorobenzoyl)benzene, and sulphonated in a controlled way until a 1.60 meq g−1 ion exchange capacity was reached. The crosslinked polysiloxane phase (PSP) was prepared by the sol-gel route from PDMS as the linear fraction and phenyltrimethoxysilane (PTMS) as crosslinker, the non-crosslinked PSP contained only PDMS. The crosslinked PSP was characterized by FTIR and solid state 29Si NMR, which revealed that the PTMS is fully crosslinked in the PSP structure. SEM micrographs of the HMs showed no apparent macro phase separation of the organic-inorganic components. The macroscopic properties of the HMs investigated were water uptake, swelling, methanol permeability and proton conductivity. The methanol permeability of the crosslinked HMs decreased to a limiting value between 16.3 and 17.9 × 10−7 cm2 s−1 at 60 °C. A continuous increase of the proton ion conductivity (64.1–90.0 mS cm−1 at 80 °C and 95% RH) was achieved with the addition of increasing amounts of the crosslinked PSP content as compared with the non-crosslinked HM. The HM with a 20 wt% of PSP presented a proton conductivity of 90.0 mS cm−1 and an activation energy for proton transport of 17.2 kJ mol−1, both comparable to Nafion 117 and in a single DMFC test the electrode assembly fabricated with this HM reached a maximum power density of 38.0 and 30.5 mW cm−2 for 2 and 5 M methanol concentrations, respectively, higher than Nafion 117 and the pristine Ph-m-SPEEKK membranes.

Polyoxometalate-Polymer Hybrid Materials as Proton Exchange Membranes for Fuel Cell Applications.

As one of the most efficient pathways to provide clean energy, fuel cells have attracted great attention in both academic and industrial communities. Proton exchange membranes (PEMs) or proton-conducting electrolytes are the key components in fuel cell devices, which require the characteristics of high proton conductivity as well as high mechanical, chemical and thermal stabilities. Organic–inorganic hybrid PEMs can provide a fantastic platform to combine both advantages of two components to meet these demands. Due to their extremely high proton conductivity, good thermal stability and chemical adjustability, polyoxometalates (POMs) are regarded as promising building blocks for hybrid PEMs. In this review, we summarize a number of research works on the progress of POM–polymer hybrid materials and related applications in PEMs. Firstly, a brief background of POMs and their proton-conducting properties are introduced; then, the hybridization strategies of POMs with polymer moieties are discussed from the aspects of both noncovalent and covalent concepts; and finally, we focus on the performance of these hybrid materials in PEMs, especially the advances in the last five years. This review will provide a better understanding of the challenges and perspectives of POM–polymer hybrid PEMs for future fuel cell applications.

Organic–inorganic hybrid proton-conducting electrolyte membranes based on sulfonated poly(arylene ether sulfone) and SiO2–SO3H network for fuel cells

A series of novel organic–inorganic hybrid proton exchange membranes (PEMs) were prepared from the sulfonated poly(arylene ether sulfone) with 4-amino phenyl pendant groups (Am-SPAES), (3-isocyanatopropyl) triethoxysilane (ICPTES), and 3-(trihydroxysilyl) propane-1-sulfonic acid with covalent bonds to form network using a sol-gel method. The obtained cross-linked hybrid membranes (Am-SPAES/I-SiO2-S) displayed excellent solvent resistance and thermal and mechanical stability. The Am-SPAES/I-SiO2-S membranes with cross-linking network exhibited a higher proton conductivity (0.043 S cm−1 at 20°C) than PEMs without covalent bonds (Am-SPAES/SiO2-S) and the swelling ratio maintained below 17.00% even at 100°C. Most importantly, all of the obtained membranes showed considerably lower methanol permeability than that of Nafion 117. In addition, the chemical structures and morphologies of the hybrid membranes were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively.

A facile route to enhance the properties of polymer electrolyte-based organic–inorganic hybrid proton exchange membranes

A series of novel sulfonated polyimide (SPI)-mesoporous organosilicate (MSiSQ) hybrid proton exchange membranes (PEMs) with enhanced properties were prepared by in situ sol–gel process. The MSiSQ was synthesized from 3-isocyanatopropyltriethoxysilane (IPTES) and 8-hydroxyquinoline-5-sulfonic acid (SQ). The microstructure and properties of the hybrid membranes were characterized. The microstructure of the membranes can be regulated by the hydrogen bonds formed by the nitrogen atoms of MSiSQ phase and the hydrogen atoms of sulfonic acid groups in SPI. The uniform distribution of sulfonate ion clusters was observed in the hybrid membranes. The hybrid membranes exhibited superior performance as compared with that of pure SPI membrane such as the proton conductivity, methanol permeability, mechanical properties and thermal stabilities. The SPI-40-MSiSQ membrane showed a maximum proton conductivity of 0.566Scm−1 at 80°C and 100% relative humidity, an optimal selectivity of 12.8×106Sscm−3 and an improved fuel cell performance as compared with pure SPI membranes. These excellent properties could be attributed to the formation of the continuous microstructure and well-connected proton transport channels due to the strong hydrogen bonding interaction and the mesoporous structure in the hybrid membranes.

Organic–inorganic hybrid proton exchange membrane based on polyhedral oligomeric silsesquioxanes and sulfonated polyimides containing benzimidazole

A new series of organic–inorganic hybrid proton exchange membranes (PEMs) were prepared using sulfonated polyimides containing benzimidazole (SPIBIs) and glycidyl ether of polyhedral oligomeric silsesquioxanes (G-POSS). SPIBIs were synthesized using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 5-amino-2-(4-aminophenyl) benzimidazole (APBIA) and 4,4′-diaminodiphenyl ether-2,2′-disulfonic acid (ODADS). The organic–inorganic cross-linked membranes can be prepared by SPIBIs with G-POSS by a thermal treatment process. The cross-linking density of the membranes was evaluated by gel fractions. The water uptake, swelling ratio, mechanical property, thermal behavior, proton conductivity, oxidative and hydrolytic stability of the cross-linked organic–inorganic membranes were intensively investigated. All the cross-linked membranes exhibit high cross-linking density for the gel fraction higher than 70%. Compared to pristine membranes (SPIBIs) and membranes without benzimidazole groups (SPI), the anti-free-radical oxidative and hydrolytic stabilities of cross-linked membranes are significantly higher. The anti-free-oxidative stability of SPIBI-100-P (cross-linked SPIBI membrane with 100% degree of sulfonation) is nearly four-fold higher than that of SPIBI-100. The proton conductivity of the cross-linked membranes ranges from 10−3 S cm−1 to 10−2 S cm−1 depending both on the degree of sulfonation (DS) of the SPIBI and temperature.

Preparation and performance of different amino acids functionalized titania-embedded sulfonated poly (ether ether ketone) hybrid membranes for direct methanol fuel cells

A series of amino acid functionalized titania submicrospheres were synthesized and incorporated into sulfonated poly (ether ether ketone) (SPEEK) to fabricate organic–inorganic hybrid proton exchange membranes. Pristine TiO2 with a uniform particle size of ~200nm were synthesized and functionalized with four kinds of amino acids including oxidized l-cysteine, O-phospho-l-serine, aspartic acid and histidine, designated as TiO2–Scys, TiO2–Pser, TiO2–Asp and TiO2–His, respectively. The effects of amino acid attribute on the membrane properties were investigated. At the filler content of 15wt%, the TiO2–Scys embedded membrane exhibited the highest proton conductivity of about 5.98×10−3Scm−1 (20°C, 100% RH), while the TiO2–His embedded membrane exhibited the lowest conductivity due to the strong acid-base interaction between the basic imidazole groups of histidine and the sulfuric acid groups of SPEEK. The TiO2–Pser embedded membrane exhibited the highest selectivity of 17.10×103Sscm−1. In addition, the methanol crossover of the hybrid membranes was reduced by two folds, and the anti-swelling property and thermal stability of the hybrid membranes were also enhanced.

A novel crosslinking organic–inorganic hybrid proton exchange membrane based on sulfonated poly(arylene ether sulfone) with 4-amino-phenyl pendant group for fuel cell application

A series of novel organic–inorganic hybrid proton exchange membranes were prepared from sulfonated poly(arylene ether sulfone) (Am-SPAES) with 4-amino-phenyl pendant group, (3-isocyanatopropyl)triethoxysilane (ICPTES) and tetraethoxysilane (TEOS) using a sol–gel method. The reactive ICPTES was used to react with the amino pendant groups of Am-SPAES to form covalent bonds between Am-SPAES and SiO2, which could effectively improve the compatibility between the polymer matrix and the inorganic SiO2 phase. The obtained hybrid membranes exhibited excellent thermal and oxidative stability. The mechanical properties of the membranes were enhanced and the swelling ratio of the membranes was reduced by introducing the cross-linking network structure. Especially, these hybrid membranes possessed higher water uptake and proton conductivities compared to the pristine Am-SPAES membrane when the SiO2 content was 3 and 6wt%, whereas the same properties of the obtained hybrid membranes decreased when the SiO2 content was 10wt%. All of the membranes showed much lower methanol permeability than Nafion 117 did. In addition, the dispersion of the inorganic particles (SiO2) in the Am-SPAES matrix could be improved by the strong covalent interactions between Am-SPAES and SiO2.

Facile in situ template synthesis of sulfonated polyimide/mesoporous silica hybrid proton exchange membrane for direct methanol fuel cells

Highly conductive and hydration retentive organic–inorganic hybrid proton exchange membranes for direct methanol fuel cells were synthesized by in situ sol–gel generation of mesoporous silica (mSiO 2) in sulfonated polyimide (SPI) via self-assembly route of organic surfactant templates for the tuning of the architecture of silica. The microstructure and properties of the resulting hybrid membranes were extensively characterized. The mesopores of about 3 nm in silica dispersion phase were formed in the SPI matrix. The existence of the mesoporous structure of silica improved the thermal stability, water-uptake and proton conductivity as well as methanol resistance of the hybrid membranes. The hybrid membrane with 30 wt.% mSiO 2 exhibited the water-uptake of 44.8% at 25 °C, and proton conductivity of 0.214 S cm −1 at 80 °C at RH = 100%, while pure SPI exhibited the values of 40.6% and 0.179 S cm −1 in the same test conditions, respectively. The results suggested that the highly hydrophilic character of Si–OH groups and the large surface area of mSiO 2 should contribute to the improvement of the water-uptake, meanwhile the mesoporous channels may supply the continuous proton conductive pathway in the hybrid membranes.

Polymeric organic–inorganic proton-exchange membranes for fuel cells produced by the sol–gel method

Approaches to the production of polymeric organic–inorganic hybrid proton-exchange membranes for fuel cells by the sol–gel method are summarized, and a classification is proposed for them. Features of the mechanism of conduction in the proton-conducting membranes are considered. Characteristics of the hybrid membranes and of fuel cells using them are presented. The main directions of research in this field are discussed.

Synthesis and characterization of new proton conducting hybrid membranes for PEM fuel cells based on poly(vinyl alcohol) and nanoporous silica containing phenyl sulfonic acid

Organic–inorganic hybrid proton exchange membranes were prepared from poly(vinyl alcohol) (PVA) and various amounts of nanoporous silica containing phenyl sulfonic acid groups. These hybrid membranes were prepared via co-condensation of functionalized nanoporous SBA-15 (SBA-ph-SO 3H) as hydrophilic inorganic modifier, glutaraldehyde (GLA) as cross-linking agent in a PVA matrix. These membranes were characterized for their morphology, thermal stability, electrochemical and physicochemical properties using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and water uptake studies. The SBA-ph-SO 3H/PVA composite membranes have a higher water retention and thermal stability than that of Nafion 117, perhaps because of responsibility of both acidic groups and nanoporous structure of silica additive. This work demonstrates the promising potential of new composite membranes for the development of high-performance and high-stability PEM fuel cells with improved proton conductivity.

Organic–inorganic hybrid proton exchange membranes based on silicon-containing polyacrylate nanoparticles with phosphotungstic acid

A series of silicon-containing polyacrylate nanoparticles (SiPANPs) were successfully synthesized by simple emulsifier-free emulsion polymerization technique. The resulting latex particles were characterized by Fourier transform infrared (FTIR) spectrometry, dynamic light scattering (DLS) analysis, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The SiPANP membranes and SiPANP/phosphotungstic acid (SiPANP/PWA) hybrid membranes were also prepared and characterized to evaluate their potential as proton exchange membranes in proton exchange membrane fuel cell (PEMFC). Compared with the pure SiPANP membrane, the hybrid membranes displayed lower thermal stability. However, the degradation temperatures were still above 190 °C, satisfying the requirement of thermal stability for PEMFC operation. In addition, the hybrid membranes showed lower water uptake but higher proton conductivity than the SiPANP precursor. The proton conductivity of the hybrid membranes was in the range of 10 −3 to 10 −2 S cm −1 and increased gradually with PWA content and temperature. The excellent hydrolytic stability was also observed in the hybrid membranes because of the existence of crosslinked silica network. The good thermal stability, reasonable water uptake, excellent hydrolytic stability, suitable proton conductivity and cost effectiveness make these hybrids quite attractive as proton exchange membranes for PEMFC applications.

Preparation of Exfoliated Zirconium Phosphate/Nafion Organic-Inorganic Hybrid Proton Exchange Membranes

A novel strategy to prepare zirconium phosphate/Nafion nanocomposite proton exchange membrane (PEM) from exfoliated zirconium phosphate and Nafion solution was proposed and investigated. It was found that zirconium phosphate could be well-dispersed and disorderly exfoliated in the membrane. Compared to neat Nafion 117 thin film, methanol permeability was reduced by 77% while the proton conductivity only decreased by 7% in the nanocomposite membrane with 3 wt % zirconium phosphate. Results obtained also showed that the addition of zirconium phosphate could increase the thermal stability of the nanocomposite PEM.