Increase In Proton Conductivity Research Articles

Investigation of thermo-mechanical behavior, proton transfer and methanol permeation of polymer electrolyte membrane in low sulfonated state modified with thermally stable surface functionalized graphene oxide nanosheets

Sulfonated polyether ether ketone is currently under investigation to replace the expensive Nafion® as polymer electrolyte membrane. Sulfonic acid group is hydrophilic in nature and plays a key role in proton transfer in polymer electrolyte membranes. The higher the degree of sulfonation the higher proton conductivity in sPEEK based polymer exchange membrane is achieved; however, high degree of sulfonation causes severe dimensional instability due to higher water uptake which in turn affects membrane fuel retention capabilities as well as thermo-mechanical strength. Graphene oxide nanosheets were functionalized with aryl dizonium salt of p-Aminobenzene sulfonic acid for modification of sPEEK in low sulfonated state (DS = 53%) to improve its proton conductivity and suppress fuel crossover. The functionalization was carried out to compensate for the possible dilution of proton exchangeable sites by fillers. The resulting membranes were characterized in terms of morphology, thermo-mechanical behavior, methanol permeability, water uptake, and proton conductivities. The results proved that sulfonated GO not only improved thermo-mechanical behavior of the membrane but also dramatically increased proton conductivity (47 mS cm−1) than pristine sPEEK (25 mS cm−1). The composite membranes showed highly reduced methanol crossover compared with pristine sPEEK. The electrochemical selectivity increased from 9.5 × 104 Scm−3s (pristine sPEEK) to 26.9 × 104 Scm−3s.

Enhanced proton conductivities of chitosan-based membranes by inorganic solid superacid SO42−–TiO2 coated carbon nanotubes

To increase proton conductivity of chitosan (CS) based polymer electrolyte membranes, a novel nanofiller-solid superacide SO42--TiO2 (STi) coated carbon nanotubes (STi@CNTs) are introduced into CS matrix to fabricate membranes for polymer electrolyte membrane fuel cells (PEMFCs). Owing to the STi coating, the dispersion ability of CNTs and interfacial bonding are obviously improved, hence, CNTs can more fully play their reinforcing role, which makes the CS/STi@CNTs composite membranes exhibit better mechanical properties than that of pure CS membrane. More importantly, STi possesses excellent proton transport ability and may create facile proton transport channels in the membranes with the help of high aspect ratio of CNTs. Particularly, the CS/STi@CNTs-1 membrane (1 wt% STi@CNTs loading) obtains the highest proton conductivity of 4.2 × 10−2 S cm–1 at 80 °C, enhancing by 80% when compared with that of pure CS membrane. In addition, the STi@CNTs also confer the composite membranes low methanol crossover and outstanding cell performance. The maximum power density of the CS/STi@CNTs-1 membrane is 60.7 mW cm−2 (5 M methanol concentration, 70 °C), while pure CS membrane produces the peak power density of only 39.8 mW cm−2.

KARAKTERISTIK MEMBRAN KOMPOSIT BERBASIS KITOSAN/PVA TERMODIFIKASI LEMPUNG DARI BABAKAN MADANG BOGOR

The use of natural polymers as membranes of DMFC from chitosan was developed because it is more environmentally friendly and has high thermal stability, but the proton conductivity is low. The Clay from Babakan Madang, which contained of SiO2 50% was expected to increase proton conductivity and improve the characteristics of the polymer membrane. Chitosan / PVA based membrane synthesis was carried out by adding clay weight variations of 0.3, 0.6 and 0.9 g. The spectra of membranes investigated by FT-IR confirmed the presence of functional groups from chitosan/PVA/clay. Morphological analysis using SEM showed that there were granules of clay dispersed on the membrane. The determination of membran conductivity using EIS showed the highest proton conductivity value was a membrane with the addition of 0.6 g clay, it was 6.96 x 10-7 S / cm. The membrane water swelling produced on the three membranes tended to be high, with the smallest value of 56.69% on the membrane with the addition of 0.9 grams of clay. The methanol uptake data found that the conductivity of membrane with the addition of 0.6 grams of clay was 346.11%.

The effect of grain size on the hydration of BaZr0.9Y0.1O3-δ proton conductor studied by ambient pressure X-ray photoelectron spectroscopy.

Three BaZr0.9Y0.1O3-δ (BZY10) pellets were prepared using different sintering processes, resulting in samples with different grain sizes, from 0.3 to 5 microns. Ambient pressure X-ray photoelectron spectra were recorded in argon, steam and oxygen atmospheres (100 mTorr) in the 300-500 °C temperature range. Deconvolution of O 1s peaks reveals 4 distinct contributions: sub-surface lattice oxide, termination layer oxides, OH- and gas-phase steam in wet environments. The OH- contribution of the O 1s peak includes sub-surface incorporation of protonic defects in the lattice related to hydration as well as surface hydroxylation and molecular water adsorption. The OH- concentration increases with grain size and with decreasing the analysis depth. These results suggest that grain boundaries associated with the larger grains adsorbed water more effectively. Thus, larger grains, which increase proton conductivity in BZY10, may also enhance catalytic activity for carbonaceous fuel oxidation by facilitating increased hydration and surface carbon removal.

Improvement of cell performance in catalyst layers with silica-coated Pt/carbon catalysts for polymer electrolyte fuel cells

Carbon-supported Pt catalysts (Pt/Cs) for use of cathode catalyst layers (CLs) for PEFCs were covered with silica layers in order to improve performance. CLs with low ratio of ionomer to carbon (I/C) for Pt/C and silica-coated Pt/C were fabricated using an inkjet printing (denoted as Pt/C(IJ) and SiO2-Pt/C(IJ)) to reduce oxygen diffusion resistance. Compared to Pt/C(IJ), SiO2-Pt/C(IJ) ink maintained good dispersion and high stability under the lower I/C. The performance of SiO2-Pt/C(IJ) was significantly higher than Pt/C(IJ) at 0.6 V under all humidity conditions. In particular, the performance of SiO2-Pt/C(IJ) under low humidity conditions showed noticeable improvement regardless of current density area. From FIB-SEM, it was confirmed that the morphologies and porosities of both catalysts were the same. Thus, these results indicate that oxygen diffusion resistance, related to structure of CLs, hardly affects the performance, whereas improved performance is attributed to increased proton conductivity by silica layers containing hydrophilic groups.

Synthesis and characterisation of PVDF-co-HFP/sTiO2 composites polymer electrolyte membranes

The Polyvinylidene fluoride (PVDF) can be combined with hexafluoropropilene (HFP) as to manifest a co-polymer called PVDF-co-HFP polymer. The PVDF-co-HFP polymer can be used as a proton exchange membrane due to its excellent mechanical strength, chemical resistance and thermal stability. It is, however, necessarily to modify the PVDF-co-HFP polymer, as an alternative to Nafion polymer membrane, by adding sulphonate groups via sulfonation and inorganic oxides such as TiO2 via oxide mixture. The research aimed to make a fuel cell membrane using PVDF-co-HFP polymer and study the effect of sulfonated TiO2 (sTiO) on the membrane to increase proton conductivity. PVDF-co-HFP membrane was prepared by which adding sTiO2 particles before it was sulfonated using 97% H2SO4. The sulfonation degree value was determined using the titration method while the proton conductivity was determined using the four-line probe. The membranes were characterised using SEM-EDX to see surface morphology and membrane composition, FTIR to confirm the presence of the -SO3H group. The results of SEM show that TiO2 particles are scattered on the surface of the membrane. EDX and FTIR results showed that sulfonation was successful in the presence of S elements by 0.77% and wavelengths 1143.2 and 1208.8 cm−1 by confirming the presence of the S=O group. The PVDF-co-HFP membrane with the addition of 3% sTiO2 particles with a sulphonation time of 6 h at 80 °C gave the best result with a proton conductivity value of 4.3 × 10−3 S cm−1 and a saturation grade of 19.37%. Thus, the PVDF-co-HFP/sTiO2 membrane can be used as a proton exchange membrane in the fuel cell.

Development of Water Vapor Transport Resistance Protocol and Analysis

W. L. Gore and Associates, Inc. (Gore) supports the lowest $/kW fuel-cell systems through development of thin, reinforced membranes, ca. 10 µm or less. Thin membranes decrease cost by reducing material content and facilitate higher performance through increased proton conductance and faster water transport. However, it has been postulated that an interfacial water transport resistance, significantly different than the bulk resistance, will dominate for thin membranes. For example, in a previous study, the interfacial effect accounted for half of the total transport resistance for a 10 µm membrane at 30% RH1. Understanding water transport through the membrane is necessary for system-level models to design optimal operation strategies. Gore implemented a protocol and analysis method for characterizing water transport properties of cation exchange membranes. Water flux is driven across the membrane by a chemical-potential gradient at different water activity levels. The water balance is tracked by monitoring the dew point at cell inlet and outlet and closes within 10%. Fick’s law is used to normalize flux data by the activity gradient across cell and inverted to calculate a total transport resistance. Cell hardware with 5 cm2 active area and straight-channel flow field configuration was used. Further details will be discussed in this presentation. Using this method, the bulk permeability of extrusion cast Nafion 11x films is 0.16 µmol/cm/s at 30% relative humidity (RH) and 95 °C, which is in agreement with literature at similar conditions1. An Evaluating the Measurement Process (EMP) study was used to quantify the amount of variation arising from measurement device and operator. With a sample size of 4, the protocol is able to detect a difference in total water transport resistance greater than 0.3 m2-s/mol. The protocol was used to study a series of 700 EW cast film thicknesses from 7 – 70 µm to separate individual contributions to the total water transport resistance, RTotal = RGas + RBulk + RInterfacial. The gas-phase transport resistance, RGas, was separated using hydrogen and nitrogen carrier gasses. The bulk water transport resistance, RBulk, is equal to thickness divided by bulk permeability. Figure 1a shows bulk permeability increases with higher water content, as expected due to the percolating network of water conducting channels2. Typically, any residual resistance is attributed to an interfacial effect, which has been rationalized by the orientation of the hydrophobic backbone toward surface2. In this study, the interfacial resistance is indistinguishable from zero. The equivalent thickness of membrane interface is shown in Figure 1b as a function of RH. ACKNOWLEDGMENTS The authors gratefully acknowledge the contribution of the Electrochemical Products team of W. L. Gore and Associates, Inc. REFERENCES Kienitz, B., Yamada, H., Nonoyama, N. & Weber, A. Z. Interfacial Water Transport Effects in Proton-Exchange Membranes. J. Fuel Cell Sci. Technol. 8, 011013-1-011013-7 (2011).Kusoglu, A. & Weber, A. Z. New Insights into Perfluorinated Sulfonic-Acid Ionomers. Chem. Rev. 117, 987–1104 (2017). Figure 1

Anomalous Appearance of a Distinct Glass Transition in Perfluoroimide Acid Ionomers

Perfluorosulfonic acid ionomers (PFSAs) are the benchmark materials used as proton exchange membranes in fuel cells due to their exceptional proton conductivity and chemical and mechanical stability. Typical PFSAs consist of a PTFE backbone with perfluoroether sidechains bearing pendant sulfonic acid groups. PFSAs of different ion contents and sidechain compositions have been developed in an effort to optimize functionality while maintaining mechanical stability. One such ionomer is 3M’s perfluoroimide acid (PFIA) containing a sulfonimide acid group in addition to the sulfonic acid on each sidechain to increase proton conductivity while preserving TFE backbone segments to maintain sufficient crystallinity. In this study, we investigate the effect of this additional acidic site on the thermomechanical properties and morphology of PFIA compared to the single acid PFSA. Utilizing alkylammonium counterions we are able to systematically manipulate the strength of the physically crosslinked network in the perfluorinated ionomers to probe the origins of thermomechanical transitions. The addition of the sulfonimide in PFIA leads to interesting differences in the morphology and thermomechanical properties including the appearance of an anomalous glass transition that is not observed in single acid PFSAs. Techniques including dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and variable temperature small angle x-ray scattering (SAXS) are utilized to probe the anomalous glass transition and assign it to the true glass transition temperature for PFIA. Figure 1

Fast Proton Conduction in Denatured Bovine Serum Albumin-Coated Nafion Membranes.

Bovine serum albumin (BSA) is a globular soluble protein, which has been extensively used in biochemical engineering. BSA materials possess abundant hydrophilic charged amino acids, H-bonded networks, and various secondary structures, which has great potential in facilitating proton transfer. Herein, BSA-N117 (BSA-Nafion 117) membranes are conveniently and eco-friendly prepared by utilizing the adsorption and denaturation of BSA on the Nafion 117 surface. The morphology and secondary structures of the BSA layer are studied with field-emission scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy. BSA-N117 membranes show highly increased proton conductivity under various conditions, which could be attributed to the improved wettability, water uptake, and the denaturation of BSA. The in-plane proton conductivity of BSA-N117-5 reaches 0.3 and 0.06 S cm-1 under 80 °C-95% RH and 100 °C-40% RH, respectively. The denaturation of BSA leads to the unfolding of α-helix structures and the formation of β-sheet structures. β-Sheet structures are more beneficial to proton conduction since β-sheet structures have stronger interactions with water molecules and protons could transport more directly in the parallel H-bonded network. Moreover, the denatured BSA modification layer could effectively help BSA-N117 membranes to possess higher selectivity and overcome the "trade-off" effect between proton conductivity and methanol resistance. The methanol permeability of BSA-N117 membranes is 1 order of magnitude lower than that of Nafion 117.

Proton Conductor-bearing Material for Enhanced Catalytic Performance of Oxygen Electrode in Unitized Regenerative Fuel Cells

There is little study on the preparation of non-conductive silica support for the fuel cell. It is expected that the sulfonation site in sulfonated silica (sSiO2) support can enhance the proton transfer property rather than the electron transfer. Therefore, we synthesize the sulfonated silica-supported Pt electrocatalyst for a bifunctional oxygen electrode in unitized regenerative fuel cell (URFC). A novel catalyst based on platinum on sulfonated SiO2 support aims for stabilizing cycle performance of URFC. It means that the usage of alternative sSiO2 is focused on suppressing the corrosion of support, whereas carbon support for the conventional oxygen electrode shows significant degradation in electrolyzer mode. In this study, the nano-morphology of our catalyst is confirmed by XRD and TEM. Electrochemical performances are analyzed by cyclic voltammetry (CV). Our new catalyst (46.1%) shows higher and stable performance during cyclic process due to the enhanced proton conduction property and low corrosion of the sulfonated silica support rather than the conventional Pt/C catalyst (45.3%). This means that the sulfonic acid functional group on the silica support can increase proton conductivity in the catalyst layer. Therefore, the ohmic resistance can decrease in the unit cell. Therefore, the sulfonated silica supported Pt electrocatalyst can be a promising candidate for bifunctional electrocatalyst in URFC.

Nafion/sulfonated poly(indene) polyelectrolyte membranes for fuel cell application

Abstract Sulfonated poly(indene) (SPInd), with 35% and 45% degree of sulfonation, was blended with Nafion to prepare blended membranes with 10, 15 and 20 wt.% of SPInd. Membranes were evaluated by infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and X-ray diffraction. Water uptake (WU), ion exchange capacity (IEC) and through-plane proton conductivity were measured. The membranes presented similar thermal stability to Nafion. WU was slightly higher for Nafion/SPInd membranes (19-21% at RT and 40-44% at 90 °C) compared with recast Nafion (16% and 34%, respectively), and IEC values showed a similar trend. Blended Nafion membranes had increased proton conductivity of 2.41 x 10-2 and 2.37 x 10-2 Scm-1 (20 wt. % of SPInd 35% and 45%, respectively), compared with 1.16 x 10-2 Scm-1 for recast Nafion. The results show that the addition of SPInd to Nafion is a potential route towards improving the performance of Nafion in proton conductivity for use in fuel cells devices.

Electrochemical methanol reformation (ECMR) using low-cost sulfonated PVDF/ZrP membrane for hydrogen production

Polymer electrolyte membrane (PEM)-based electrochemical methanol reformation has gained interest as a practical way to produce hydrogen than water electrolysis due to its low operating voltages. Development of alternative PEM for this application is of considerable interest in order to reduce the cost as well as increase the system efficiency. Presently, a novel SPVDF/ZrP composite membrane was synthesized as proton exchange membrane for hydrogen production using electrochemical methanol reformation (ECMR). PVDF-co-HFP granules were defluorinated by alkali treatment followed by sulfonation using chlorosulfonic acid to prepare sulfonated polymer. Inorganic zirconium phosphate (ZrP) was further added to increase proton conductivity. The membranes were characterized for their physicochemical properties, mechanical strength, and thermal stability. The enhancement in proton exchange capacity and water uptake with adequate dimensional stability was observed with dehydrofluorination and impregnation of ZrP. A novel electrolyzer consisting of Pt-Ru/C as anode electrode, same format as anode as cathode electrode and the SPVDF/ZrP composite membrane was assembled and its performance was tested for hydrogen production. It was found that SPVDF/ZrP composite membrane showed good electrochemical cell performance of 0.65 V at 0.15 A cm−2 current density at ambient temperature and gives scope for operating ECMR cell at higher current densities for to increase the hydrogen production rate which is comparable to the performance of commercial Nafion® 117 membrane.

Stable nanofibrous poly(aryl sulfone ether benzimidazole) membrane with high conductivity for high temperature PEM fuel cells

Novel electrospun nanofiber poly(aryl sulfone ether benzimidazole) (SO2-OPBI) membrane is synthesized for enhanced the proton conductivity and chemical stability. Incorporation of the flexible aryl sulfone- and ether-linkages in the polymer backbone are improved the physico-chemical properties of membranes. We prepared different types of membranes, namely dense SO2-OPBI membrane, nanofiber SO2-OPBI and m-PBI membrane and evaluated their physico-chemical properties for suitability application of high temperature PEM fuel cells. Interestingly, the nanofiber membranes possessed a greatly increased proton conductivity (0.0667 S cm−1 at 160 °C and acid doped level of 338%), which is comparable to that of the dense membrane (0.033 S cm−1 at 160 °C and 221% acid doping). The nanofiber and dense membrane shows good oxidative stability under Fenton reagent.

Enhancing proton conductivity via sub-micron structures in proton conducting membranes originating from sulfonated PVDF powder by radiation-induced grafting

We report here submicron-structured proton conducting poly(vinylidene fluoride)-graft-poly(styrene sulfonic acid) (PVDF-g-PSSA) membranes for polymer electrolyte membrane fuel cells (PEMFC). Highly conductive proton exchange membranes were obtained by single-step radiation grafting of sodium styrene sulfonate (SSS) to powder-form PVDF, followed by casting and subsequent solvent evaporation. The obtained submicron structure of membrane through solvent evaporation led to the arrangement of ionic channels proving increasing proton conductivity with the increase in graft level. In addition, a temperature above melting point of PVDF was used for solvent evaporation to allow melted PVDF to fill the formed pores, providing denser structure resulting in improved mechanical properties of the membranes. SSS grafting to PVDF powder was verified by NMR spectroscopy, and resultant membranes were characterized for proton conductivity, water up-take, morphology, mechanical and thermal properties, and fuel cell performance. According to preliminary tests, proton conductivities which were observed to increase with graft level were found to be around 70mScm2 at 35% graft level. Thus, this led to a promising power density of 250mW/cm2 at 650mA/cm2.

Quantifying Site-Specific Proton Dynamics in Phosphate Solid Acids by 1H Double Quantum NMR Spectroscopy

Solid-state magic angle spinning (MAS) NMR was used to investigate changes in proton dynamics in phosphate solid acids that exhibited increased proton conductivity between room temperature and 110 °C. Double quantum dipolar recoupling methods were used to quantify site-specific changes in proton–proton dipolar coupling as a function of temperature. The static dipolar coupling and motionally induced changes to it were compared. This was accomplished by calculating (from crystal structures) and measuring (from the initial parts of the DQ recoupling curves) the root-sum-square of the dipolar coupling, a geometry-independent measure of dipolar coupling strength referred to as the “apparent dipolar coupling”, Dapp. The analysis of KH2PO4 and RbH2PO4 showed that the experimentally determined apparent dipolar couplings were reduced from the calculated values at increased temperatures in dynamic systems. Higher proton conductivity was associated with greater reduction of the apparent dipolar coupling as measured ...

Interfacial Water Drives Improved Proton Transport in Siliceous Nanocomposite Nafion Thin Films.

Nafion proton exchange membranes dehydrate when they are used in the gas phase and in high-temperature applications, such as fuel cells and (photo)electrolysis. Retaining a high level of membrane hydration under such conditions can be achieved by using inorganic fillers, but has never been demonstrated for thin films. Herein, several types of siliceous nanoparticles were incorporated for the first time into Nafion thin films. For composite Nafion materials, increased water uptake does not always induce increased proton conductivity. Here, increased water uptake did result in higher proton conductivity due to a synergistic effect within the composite film. The nanocomposites displayed a higher water uptake than could be expected based on the water uptake of the individual materials. Excess water present at the Nafion-filler interface was found to cause the proton conductivity of nanocomposite Nafion/Ludox AS-40 thin films to double compared with pristine Nafion at low relative humidity (from 2 to 4 mS cm-2 ). Knowledge about the properties of such interfaces will allow for the better design of self-humidifying nanocomposite Nafion membranes, films, and catalyst layers.

Low permeable composite membrane based on sulfonated poly(phenylene oxide) (sPPO) and silica for vanadium redox flow battery

The proton conductivity and vanadium permeability of organic-inorganic (sulfonated poly (phenylene oxide) (sPPO)-nano sized sulfonated silica (sSiO2)) hybrid membrane were investigated for application in a vanadium redox flow battery (VRFB) system. Significant attention is being paid to PPO polymers as a replacement for Nafion® membranes due to their relatively low cost and ease of sulfonation. The attachment of a sulfonic acid (SO3H) functional group to PPO and SiO2 was confirmed using Fourier Transform Infrared Spectroscopy (FTIR). The hybrid membrane (sPPO-2% sSiO2) exhibited increased thermal stability, water uptake (WU), ion exchange capacity (IEC) and proton conductivity (IC) compared with a conventional organic sPPO membrane. The proton conductivity of the hybrid membrane increased considerably compared to sPPO alone, resulting from the 2% sSiO2 nanoparticles added homogeneously to the polymer matrix. The proton conductivities of the sPPO and hybrid membranes were 0.050 and 0.077 S/cm, respectively. The increased proton conductivity of the hybrid membrane was attributed to the enhanced hydrophilic properties of SO3H in the membranes. In addition, inorganic particles in the polymer matrix acted as a barrier for vanadium ion crossover. During VRFB unit cell operation, vanadium ion (VO2+) crossovers were measured as 14.66, 1.955 and 0.173 mmol L−1 through Nafion®212, sPPO and hybrid membranes, respectively, and VO2+ permeability were 2.22 × 10−7, 2.50 × 10−8 and 4.76 × 10−9 cm2 min−1 for Nafion®212, sPPO and hybrid membranes, respectively. Based on our experimental results, low cost organic-inorganic hybrid membranes as prepared provide an efficient alternative membrane material for advanced VRFB systems.

Novel proton exchange membrane nanocomposites based on sulfonated tungsten trioxide for application in direct methanol fuel cells

Novel sulfonated poly (phthalazinone ether ketone) (SPPEK)/sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (SPVdF-co-HFP)/sulfonated tungsten trioxide (SWO3) nanocomposite blend membranes were fabricated as alternative proton exchange membranes (PEM) for application in direct methanol fuel cell (DMFC). PPEK and PVdF-co-HFP were sulfonated using sulfuric acid and chlorosulfonic acid, respectively. The degree of sulfonation (DS) of produced SPPEK and SPVdF-co-HFP were determined by titration method and found to be 68% and 30%, respectively. The dominant characteristics of the prepared membranes, such as water uptake, membrane swelling, proton conductivity, methanol permeability, selectivity and DMFC performance were investigated. The membranes containing SWO3 nanoparticles indicated higher proton conductivity and lower methanol permeability compared with pristine SPPEK and blend membranes. This improvement is attributed to presence of the sulfonated groups of nanoparticles that increases proton conductivity with Grotthus and vehicle mechanisms. The catalytic properties of SWO3 nanoparticles increase kinetic of reaction in interface surface of membrane and electrode and improve performance of DMFCs. Well optimized nanocomposite blend membrane (MSSW5) showed proton conductivity of 0.071 S cm−1, methanol permeability of 9.5 × 10−8 cm2 S−1 and power density of 63.60 mW cm−2 at room temperature, thus it can be a suitable candidate for DMFC application.

Characterization of highly sulfonated PEEK based membrane for the fuel cell application

In this study, poly(bisphenol-A-ether ketone) (PBAEK) is synthesized via nucleophilic aromatic substitution poly condensation between bisphenol A and 4,4-difluorobenzophenone, and the synthesized polymers are sulfonated using chlorosulfuric acid and suitable synthesis conditions for the temperature and sulfonating reagent content. The sulfonation degree of polymer is calculated using element analyses. The prepared sulfonated polymers are characterized for potential fuel cell applications through determining their water uptake, proton conductivity, and thermal stability. The significant advantage of the synthesized sulfonated PBAEK (sPBAEK) is its better solubility relative to commercial PEEK in various solvents, because sPBAEK backbones contain bisphenol A. The water uptake of the membrane increases with increases in the sulfonation degree. The sPBAEK membrane exhibits increased proton conductivity compared with the PBAEK membrane at 100% relative humidity conditions. As the sulfonation degree increases, the proton conductivity increases due to the increasing content in the hydrophilic domain. This property allows the prepared membranes to be potential candidates for proton exchange membrane fuel cells.

X-ray diffraction investigations of structural modifications in In-doped tin pyrophosphates

Laboratory and synchrotron x-ray powder diffraction were used to investigate the structural modifications that occur upon indium doping of tin pyrophosphate. The data collected under air, vacuum, and inert gas sample environments at temperatures (T) from 50 °C to 300 °C show that regardless of the In-doping level (0 ≤ x ≤ 0.18) all InxSn1-xP2O7 samples are isomorphic (have the same P a -3 cubic crystal structure) at all temperatures and under all the conditions investigated. The cubic lattice parameter (a) increases linearly with T at all doping levels, but the “a vs. x|T“ isotherms exhibit a robust peak at x = 0.1 when data are collected on samples measured in air. On the other hand, Rietveld refinements against data collected on InxSn1-xP2O7 samples yield values of OO bond lengths and POP bond angles that show no major changes at x = 0.1 at any temperature. This is significant, as the Sn0.9In0.1P2O7 (x = 0.1) compound is known to exhibit the highest proton conductivity within the series, but the microscopic details responsible for the increased proton conductivity are not understood. Finally, the peak observed in the “a vs. x|T“ curves vanishes if the measurements are taken on samples kept either under vacuum or in an inert gas environment. This is a remarkable behavior as it lends further support to our hypothesis that a key microscopic feature responsible for the large proton conductivity of the Sn0.9In0.1P2O7 compound is the enlargement of the lattice constant at x = 0.1.