Constructing a long-range proton conduction bridge in sulfonated polyetheretherketone membranes with low DS by incorporating acid-base bi-functionalized metal organic frameworks

Functionalized metal-organic frameworks (MOFs) are being extensively developed as viable fillers to enhance the proton conductivity of proton exchange membranes. Herein, an amino-pendant sulfonic acid bi-functionalized MOFs material (UNCS)-doped SPEEK membrane with low degree of sulfonation (DS) can improve the proton conductivity as well as maintain the membrane dimensional stability. UNCS can act as bridges of proton donors and acceptors to reduce the activation energy barrier and shorten the distance of long-range proton conduction. Among all as-prepared membranes, SPEEK/UNCS-3 exhibited the highest proton conductivity of 186.4 mS·cm^?1 at 75 °C and 100% relative humidity (RH), which is much greater than that of pristine SPEEK and Nafion 117. Benefiting from the acid-base pair interaction between the amino groups of UNCS and the sulfonic acid groups of SPEEK, the dimensional stability and mechanical properties of the composite membranes were enhanced. More interestingly, STEM-HAADF and SAXS characterization consistently revealed that UNCS served as bridges among proton channels in the composite membranes for continuous proton transport.     

Effect of cesium salt of tungstophosphoric acid (Cs-TPA) on the properties of sulfonated polyether ether ketone (SPEEK) composite membranes for fuel cell applications

We have prepared composite membranes for fuel cell applications. Cesium salt of tungstophosphoric acid (Cs-TPA) particles was synthesized by aqueous solutions of tungstophosphoric acid and cesium hydroxide and, Cs-TPA particles and sulfonated (polyether ether ketone) (SPEEK) with two sulfonation degrees (DS), 60 and 70%have been used. We examined both the effects of Cs-TPA in SPEEK membranes as functions of sulfonation degrees of SPEEK and the content of Cs-TPA. The performance of the composite membranes was evaluated in terms of water uptake, ion exchange capacity, proton conductivity, chemical stability, hydrolytic stability, thermal stability and methanol permeability. The morphology of the membranes was investigated with SEM micrographs. Increasing sulfonation degree of SPEEK from 60 to 70 caused agglomeration of the Cs-TPA particles. The methanol permeability was reduced to 4.7 × 10⁻⁷ cm²/s for SPEEK (DS: 60%)/Cs-TPA membrane with 10 wt.% Cs-TPA concentration, and acceptable proton conductivity of 1.3 × 10⁻¹ S/cm was achieved at 80 °C under 100% RH. The weight loss at 900 °C increased with the addition of inorganic particles, as expected. The hydrolytic stability of the SPEEK/Cs-TPA based composite membranes was improved with the incorporation of the Cs-TPA particles into the matrix. We also noted that SPEEK60/Cs-TPA composite membranes were hydrolytically more stable than SPEEK70/Cs-TPA composite membranes. On the other hand, Methanol, water vapor, and hydrogen permeability values of SPEEK60 composite membranes were found to be lower than that of Nafion^®.     

Effect of functionality of polyhedral oligomeric silsesquioxane [POSS] on the properties of sulfonated poly(ether ether ketone) [SPEEK] based hybrid nanocomposite proton exchange membranes for fuel cell applications

Organic–inorganic hybrid nanocomposite membranes were prepared using three different types of POSS i.e., PEG POSS^® cage mixture (PPOSS), trisilanol phenyl POSS^® (TSP POSS) and trisulfonic acid isobutyl POSS^® (SPOSS) at a fixed loading of 2% (w/w) as filler and SPEEK with degree of sulfonation (DS) 55% as polymer matrix. The influence of POSS functionality on hybrid membrane's thermo-mechanical properties, morphology, water uptake and proton conductivity was investigated. Thermal and mechanical stability of hybrid membranes increased upon incorporation of POSS. The size and distribution of POSS particles into SPEEK matrix was studied using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) and it was found that TSP POSS and PPOSS based membranes showed smaller particle size and uniform distribution as compared to SPOSS based membranes which consequently affect the water uptake and proton conductivity of these hybrid membranes. The water uptake studies were carried out at three different temperatures i.e. 30, 80, 100 °C for 24 h and POSS based composite membranes showed higher water uptake and proton conductivity compared to neat SPEEK membranes. The highest proton conductivity (64.6 mS/cm) was observed for TSP POSS containing membrane which is more than double of neat SPEEK (31.3 mS/cm) membrane. The composite membrane containing TSP POSS can be considered as suitable membrane for PEMFCs applications.     

Evaluation of SPEEK/PBI blend membranes for possible direct borohydride fuel cell (DBFC) application

Direct Borohydride Fuel Cell (DBFC) is one of the most promising liquid fuel cell technologies. However, similar to the other classes of fuel cells, there are technical problems to be solved and new materials specific to the technology should be developed for each component. The electrolyte membrane is one of the key components for its success similar to the other FC types. Commercial perfluorosulfonic acid type membranes namely Nafion^® is still the first choice in relatively less number of DBFC studies. In this study, less costly blend membranes were fabricated and characterized for comparison of the key properties with Nafion^® especially for DBFC application. For this purpose, the selected base polymer poly ether-ether-ketone (PEEK) was sulfonated up to high degrees of sulfonation (DS) and blended with another base polymer polybenzimidazole (PBI) at various ratios. Key electrolyte membrane properties such as DS, water uptake, ionic conductivity, BH₄⁺ fuel crossover, mechanical strength and glass transition temperature (T_g) were investigated by proton nuclear magnetic resonance spectroscopy (H NMR), electrochemical impedance spectroscopy (EIS), voltammetry, universal testing machine and Differential Scanning Calorimetry (DSC) respectively. Finally single cell test performances were investigated in a DBFC test system. Results showed that the mechanical strength of SPEEK which has a good ionic conductivity value could be improved well beyond the value of Nafion 117 without sacrificing too much of the conductivity. It has been observed that there is a trade-off between the important properties such as ionic conductivity, fuel (borohydride) permeability and mechanical strength at the first sight. The peak power densities obtained for blend membranes are close to the value of the commercial Nafion^® 117 membrane. These results show that these blend membranes have a potential that can be improved for direct borohydride fuel cells.     

Cross-linked membranes based on sulfonated poly (ether ether ketone) (SPEEK)/Nafion for direct methanol fuel cells (DMFCs)

A series of cross-linked membranes based on SPEEK/Nafion have been prepared to improve methanol resistance and dimension stability of SPEEK membrane for the usage in the direct methanol fuel cells (DMFCs). Sulfonated diamine monomer is synthesized and used as cross-linker to improve the dispersion of Nafion in the composite membranes and decrease the negative effect of cross-linking on proton conductivity of membranes. FT-IR analysis shows that the cross-linking reaction is performed successfully. The effects of different contents of Nafion on the properties of cross-linked membranes are investigated in detail. All the cross-linked membranes show lower methanol permeability and better dimensional stability compared with the pristine SPEEK membrane. SPEEK-N30 with the 30 wt % Nafion shows a methanol permeability of 0.73 × 10⁻⁶ cm² s⁻¹ and a water uptake of 24.4% at 25 °C, which are lower than those of the pristine membrane. Meanwhile, the proton conductivity of SPEEK-N30 still remains at 0.041 S cm⁻¹ at 25 °C, which is comparable to that of the pristine SPEEK membrane. All the results indicate that these cross-linked membranes based on SPEEK/Nafion show good prospect for the use as proton exchange membranes.     

Improving the proton conductivity of sulfonated poly (ether ether ketone) membranes by incorporating a crystalline nanoassembly of trimesic acid and melamine

A novel proton exchange membrane was synthesized by embedding a crystalline which was nano-assembled through trimesic acid and melamine (TMA·M) into the matrix of the sulfonated poly (ether ether ketone) (SPEEK) to enhance the proton conductivity of the SPEEK membrane. Fourier transform infrared indicated that hydrogen bonds existed between SPEEK and TMA·M. XRD and SEM indicated that TMA·M was uniformly distributed within the matrix of SPEEK, and no phase separation occurred. Thermogravimetric analysis showed that this membrane could be applied as high temperature proton exchange membrane until 250 °C. The dimensional stability and mechanical properties of the composite membranes showed that the performance of the composite membranes is superior to that of the pristine SPEEK. Since TMA·M had a highly ordered nanostructure, and contained lots of hydrogen bonds and water molecules, the proton conductivity of the SPEEK/TMA·M-20% reached 0.00513 S cm⁻¹ at 25 °C and relative humidity 100%, which was 3 times more than the pristine SPEEK membrane, and achieved 0.00994 S cm⁻¹ at 120 °C.     

Effects of sulfonated polyether-etherketone (SPEEK) and composite membranes on the proton exchange membrane fuel cell (PEMFC) performance

Sulfonated polyether-etherketone (SPEEK) has a potential for proton exchange fuel cell applications. However, its conductivity and thermohydrolytic stability should be improved. In this study the proton conductivity was improved by addition of an aluminosilicate, zeolite beta. Moreover, thermohydrolytic stability was improved by blending poly-ether-sulfone (PES). Sulfonated polymers were characterized by H-NMR. Composite membranes prepared were characterized by Electrochemical Impedance Spectroscopy (EIS) for their proton conductivity. Degree of sulfonation (DS) values calculated from H-NMR results, and both proton conductivity and thermohydrolytic stability was found to strongly depend on DS. Therefore, DS values were controlled time in the range of 55–75% by controlling the reaction time. Zeolite beta fillers at different SiO₂/Al₂O₃ ratios (20, 30, 40, 50) were synthesized and characterized by XRD, EDX, TGA, and SEM. The proton conductivity of plain SPEEK membrane (DS = 68%) was 0.06 S/cm at 60 °C and the conductivity of the composite membrane containing of zeolite beta filled SPEEK was found to increase to 0.13 S/cm. Among the zeolite Beta/SPEEK composite membranes the best conductivity results were achieved with zeolite beta having a SiO₂/Al₂O₃ ratio of 50 at 10 wt% loading.     

An effective strategy to enhance the performance of the proton exchange membranes based on sulfonated poly(ether ether ketone)s

We report an effective and facile approach to enhance the dimensional and chemical stability of sulfonated poly(ether ether ketone) (SPEEK) type proton exchange membranes through simple polymer blending for fuel cell applications, using commercial available materials. The polymeric blends with sulfonated poly(aryl ether sulfone)s (SPAES) were simply fabricated by a three-component system, which contained SPEEK (10–50 wt%, 1.83 mmol/g), and SPAES-40 (1.72 mmol/g)/SPAES-50 (2.04 mmol/g) at 1:1 in weight. The SPAES-40 was selected for mechanical and dimensional stability reinforcing, while SPAES-50 for the good polymer compatibility. The obtained SPEEK/SPAES blend membranes showed depressed water uptake, better dimensional and oxidative stability, together with higher proton conductivity beyond 70 °C than the pristine SPEEK membrane. The apparent improvements in membrane properties were associated with the homogeneous dispersion of SPEEK and both SPAES copolymers inside the membranes as well as the rearrangements of the polymeric chains. The SPEEK content should be properly controlled in the range of 10–40% (B10 to B40). In a H₂/O₂ fuel cell test, B30 showed a maximum power density of 700 mW/cm², which was 1.6 times as high as that of B40 at 80 °C under 100% RH. The further cross-linking treatment produced more ductile and enduring blend membranes, indicating an appreciable prospective for fuel cell applications.     

Enhanced properties of SPEEK with incorporating of PFSA and barium strontium titanate nanoparticles for application in DMFCs

Novel blend nanocomposite proton‐exchange membranes were prepared using sulfonated poly (ether ether ketone) (SPEEK), perfluorosulfonic acid (PFSA), and Ba_0.9Sr_0.1TiO₃ (BST) doped‐perovskite nanoparticles. The membranes were evaluated by attenuated total reflection, X‐ray diffraction spectroscopy, water uptake, proton conductivity, methanol permeability, and direct methanol fuel cell test. The effect of two additives, PFSA and BST, were investigated. Results indicated that both proton conductivity and methanol barrier of the blend nanocomposite membranes improved compared with pristine SPEEK and the as‐prepared blend membranes. The methanol permeability and the proton conductivity of the blend membrane containing 6 wt% BST obtained 3.56 × 10^?7 cm² s^?1 (at 25 °C) and 0.110 S cm^?1 (at 80 °C), respectively. The power density value for the optimum blend nanocomposite membrane (15 wt% PFSA and 6 wt% BST) (54.89 mW cm^‐2) was higher than that of pristine SPEEK (31.34 mW cm^‐2) and SPF15 blend membrane (36.12 mW cm^‐2).     

Sulfonated poly(ether ether ketone)/poly(ether sulfone) composite membranes as an alternative proton exchange membrane in microbial fuel cells

Custom-made proton exchange membranes (PEM) are synthesized by incorporating sulfonated poly(ether ether ketone) (SPEEK) in poly(ether sulfone) (PES) for electricity generation in microbial fuel cells (MFCs). The composite PES/SPEEK membranes at various composition of SPEEK are prepared by the phase inversion method. The membranes are characterized by measuring roughness, proton conductivity, oxygen diffusion, water crossover and electrochemical impedance. The conductivity of hydrophobic PES membrane increases when a small amount (3–5%) of hydrophilic SPEEK is added. The electrochemical impedance spectra shows that the conductivity and capacitance of PES/SPEEK composite membranes during MFC operation are reduced from 6.15 × 10⁻⁷ to 6.93 × 10⁻⁵ (3197 Ω–162 Ω) and from 3.00 × 10⁻⁷ to 1.56 × 10⁻³ F, respectively when 5% of SPEEK added into PES membrane. The PES/SPEEK 5% membrane has the highest performance compared to other membranes with a maximum power density of 170 mW m⁻² at the maximum current density of 340 mA m⁻². However, the interfacial reaction between the membrane and the cathode with Pt catalyst indicates moderate reaction efficiency compared to other membranes. The COD removal efficiency of MFCs with composite membrane PES/SPEEK 5% is nearly 26-fold and 2-fold higher than that of MFCs with Nafion 112 and Nafion 117 membranes respectively. The results suggest that the PES/SPEEK composite membrane is a promising alternative to the costly perfluorosulfonate membranes presently used as separators in MFC systems.     

Enhancement of proton conductivity of polymer electrolyte membrane enabled by sulfonated nanotubes

Proton exchange membrane (PEM) with high proton conductivity is crucial to the commercial application of PEM fuel cell. Herein, sulfonated halloysite nanotubes (SHNTs) with tunable sulfonic acid group loading were synthesized and incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix to prepare nanocomposite membranes. Physicochemical characterization suggests that the well-dispersed SHNTs enhance the thermal and mechanical stabilities of nanocomposite membranes. The results of water uptake, ionic exchange capacity, and proton conductivity corroborate that the embedded SHNTs interconnect the ionic channels in SPEEK matrix and donate more continuous ionic networks. These networks then serve as proton pathways and allow efficient proton transfer with low resistance, affording enhanced proton conductivity. Particularly, incorporating 10% SHNTs affords the membrane a 61% increase in conductivity from 0.0152 to 0.0245 S cm⁻¹. This study may provide new insights into the structure-properties relationships of nanotube-embedded conducting membranes for PEM fuel cell.     

SPEEK proton exchange membranes modified with silica sulfuric acid nanoparticles

In order to increase both of the water uptake and conductivity, the proton exchange membranes were fabricated by sulfonated poly(ether ether ketone) (SPEEK) doped with varied contents of silica sulfuric acid (SSA) which is obtained by treating SiO₂ nanoparticles with more volatile SO₂Cl₂. SEM images of the composite membranes show that SSA nanoparticles are dispersed within the membranes uniformly, indicating the good organic compatibility of SSA particles. TEM images show that the composite membranes have improved ionic clusters distribution. The water uptakes of the composite membranes in water and under low relative humidities are all higher than that of the pristine SPEEK membrane. The addition of SSA enhances the conductivity obviously. The composite membrane containing 5wt.% SSA exhibits the highest conductivity of 0.13 Scm⁻¹ at 80 °C, approximately 18.6% higher than that of the pristine SPEEK membrane and 8.6% higher than that of Nafion117. The composite membranes also show good thermal stability. These results imply the potential application of the SPEEK/SSA composite membranes as improved PEMs in PEMFC.     

Experimental Investigation of boron phosphate Incorporated speek/pvdf blend membrane for proton exchange membrane fuel cells

The recent studies focused on the blend membranes to a great extent due to their capability of gathering some important polymer characteristic features. In this survey, boron phosphate (BP) doped sulfonated poly (ether ether ketone)/Poly (vinylidene fluoride) (SPEEK/PVDF) blend membrane having high ionic conduction capability was synthesized. The boron phosphate doping to the membrane matrix enhanced the membrane properties in terms of proton exchange membrane conditions. The sol-gel and casting method was used to synthesise the SPEEK/PVDF blend membrane. The characterization tests to observe the structure of the membrane, such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), FT-IR and mechanical/thermal stability tests were conducted. The membrane ionic transportation and water retention were improved directly by the addition of boron phosphate. The highest power density (242 mW cm^?2) and current density (400 mA cm^?2) at 0.6 V were obtained by SPEEK/PVDF/10BP, respectively. Additionally, the proton conductivity value of 39 mS cm^?1 was obtained for SPEEK/PVDF/10BP sample at 80 °C. The authors concluded that both boron phosphate additive and SPEEK/PVDF blend membrane have promising results for fuel cell future operations.     

Investigation of the effects of AMPS-modified nanoclay on fuel cell performance of sulfonated aromatic proton exchange membranes

Here we describe preparation and characterization of a series of nanocomposite polyelectrolytes based on partially sulfonated poly (ether ether ketone) (SPEEK) and organically modified montmorillonite (MMT). Optimum degree of sulfonation for SPEEK is selected based on its transport properties. MMT is modified via ion exchange reaction using a 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as a functional modifier. AMPS-MMT at different loadings is introduced into the SPEEK matrices via the solution intercalation technique. Also, the nanocomposite membranes are fabricated using SPEEK and commercially available nanoclays like Cloisite Na (Na-MMT) and Cloisite 15A. Transport properties, proton conductivity and methanol permeability of the fabricated composite membranes are evaluated. Presence of AMPS-MMT significantly decreases the activation energy needed for proton conductivity. A membrane based on SPEEK/AMPS-MMT-3 wt% is selected as an optimum formulation which exhibits a high selectivity and power density at the elevated methanol concentrations. Moreover, it is found that the optimum nanocomposite membrane not only provides higher power output compared to the neat SPEEK and Nafion^®117 membranes, but also exhibits a higher open circuit voltage (OCV) in comparison with pristine SPEEK and commercial Nafion^® 117 membranes. Owing to the desirable transport and electrochemical properties SPEEK/AMPS-MMT nanocomposite can be considered as an alternative membrane for direct methanol fuel cell applications.     

Composite membrane by incorporating sulfonated graphene oxide in polybenzimidazole for high temperature proton exchange membrane fuel cells

The objective of this work is to examine the polybenzimidazole (PBI)/sulfonated graphene oxide (sGO) membranes as alternative materials for high-temperature proton exchange membrane fuel cell (HT-PEMFC). PBI/sGO composite membranes were characterized by TGA, FTIR, SEM analysis, acid doping&acid leaching tests, mechanical analysis, and proton conductivity measurements. The proton conductivity of composite membranes was considerably enhanced by the existence of sGO filler. The enhancement of these properties is related to the increased content of –SO₃H groups in the PBI/sGO composite membrane, increasing the channel availability required for the proton transport. The PBI/sGO membranes were tested in a single HT-PEMFC to evaluate high-temperature fuel cell performance. Amongst the PBI/sGO composite membranes, the membrane containing 5 wt. % GO (PBI/sGO-2) showed the highest HT-PEMFC performance. The maximum power density of 364 mW/cm² was yielded by PBI/sGO-2 membrane when operating the cell at 160 °C under non humidified conditions. In comparison, a maximum power density of 235 mW/cm² was determined by the PBI membrane under the same operating conditions. To investigate the HT-PEMFC stability, long-term stability tests were performed in comparison with the PBI membrane. After a long-term performance test for 200 h, the HT-PEMFC performance loss was obtained as 9% and 13% for PBI/sGO-2 and PBI membranes, respectively. The improved HT-PEMFC performance of PBI/sGO composite membranes suggests that PBI/sGO composites are feasible candidates for HT-PEMFC applications.     

Proton conduction of novel calcium phosphate nanocomposite membranes for high temperature PEM fuel cells applications

This work describes the synthesis and evaluation of nanocomposite membranes based on calcium phosphate (CP)/ionic liquids (ILs) for high-temperature proton exchange membrane (PEM) fuel cells. Several composite membranes were synthesized by varying the mass ratios of ILs with respect to the CP and all supported on porous polytetrafluoroethylene (PTFE). The membranes exhibit high proton conductivities. Two ionic liquids were investigated in this study, namely, 1-Hexyl-3- methylimidazolium tricyanomethanide, [HMIM][C₄N₃⁻], and 1-Ethyl-3-methylimidazolium methanesulfonate, [EMIM][CH₃O₃S⁻]. At room temperature, the CP/PTFE/[HMIM][C₄N₃⁻] composite membrane possessed a high proton conductivity of 0.1 S cm⁻¹. When processed at 200 °C, and fully anhydrous conditions, the membrane showed a conductivity of 3.14 × 10⁻³ S cm⁻¹. Membranes based on CP/PTFE/[EMIM][CH₃O₃S⁻] on the other hand, had a maximum proton conductivity of 2.06 × 10⁻³ S cm⁻¹ at room temperature. The proton conductivities reported in this work appear promising for the application in high-temperature PEMFCs operated above the boiling point of water.     

Nafion/Pd–SiO2 nanofiber composite membranes for direct methanol fuel cell applications

One of the major challenges for direct methanol fuel cells is the problem of methanol crossover. With the aim of solving this problem without adverse effects on the membrane conductivity, Nafion/Palladium–silica nanofiber (N/Pd–SiO₂) composite membranes with various fiber loadings were prepared by a solution casting method. The silica-supported palladium nanofibers had diameters ranging from 100 nm to 200 nm and were synthesized by a facile electro-spinning method. The thermal properties, ionic exchange capacities, water uptake, proton conductivities, methanol permeabilities, chemical structures, and micro-structural morphologies were determined for the prepared membranes. It was found that the transport properties of the membranes were affected by the fiber loading. All of the composite membranes showed higher water uptake and ion exchange capacities compared to commercial Nafion 117 and proved to be thermally stable for use as proton exchange membranes. The composite membranes with optimum fiber content (3 wt%) showed an improved proton conductivity of 0.1292 S cm⁻¹ and a reduced methanol permeability of 8.36 × 10⁻⁷ cm² s⁻¹. In single cell tests, it was observed that, the maximum power density measured with composite membrane is higher than those of commercial Nafion 117.     

Sulfonic acid functionalized graphene oxide paper sandwiched in sulfonated poly(ether ether ketone): A proton exchange membrane with high performance for semi-passive direct methanol fuel cells

Sulfonated poly(ether ether ketone) (SPEEK) membranes have been deposited on the both sides of a sulfonic acid functionalized graphene oxide (SGO) paper to form a proton exchange membrane (PEM) with a sandwiched structure. The obtained SPEEK/SGO/SPEEK membrane could exhibit proton conductivity close to Nafion^® 112 and lower methanol permeability. The use of this SPEEK/SGO/SPEEK membrane greatly improves the performance of the semi-passive direct methanol fuel cell (DMFC). The semi-passive DMFC with the SPEEK/SGO/SPEEK membrane is found to be capable of delivering the peak power density 60% higher than that with the commercial Nafion^® 112. This, along with its comparable durability to Nafion^® 112, strongly suggests the great promise of using the SPEEK/SGO/SPEEK membrane as the PEM.     

Conductivity of aromatic-based proton exchange membranes at subzero temperatures

Stable proton exchange membrane (PEM) with good proton conductivity at subzero temperatures is important for the development of PEM fuel cell cold start. In this work, subfreezing conductivity was reported for several aromatic-based PEMs including sulfonated polyimides (SPIs) with three values of ion-exchange capacity (IEC), sulfonated poly(ether ether ketone) (SPEEK) and disulfonated poly(arylene ether sulfone) copolymer (SPSU) as well as Nafion^® 212. Measurements were performed using the electrochemical impedance spectroscopy (EIS) technique. The results showed that only fully hydrated SPEEK (IEC, 1.75) and SPSU (IEC, 2.08) had comparable conductivities with Nafion^® 212 at subzero temperatures. Considering implement of gas purge before subzero storage of PEM fuel cell, the conductivity for those PEMs humidified by water vapor at activity of 0.75 was also investigated. The state of water in aromatic-based PEMs was quantified by differential scanning calorimetry (DSC), and its correlation with conductivity of the membrane was also discussed.     

Enhancement of fuel cell properties in polyethersulfone and sulfonated poly (ether ether ketone) membranes using metal oxide nanoparticles for proton exchange membrane fuel cell

The proton exchange membrane (PEM) was synthesized using polyethersulfone (PES), sulfonated poly (ether ether ketone) (SPEEK) and nanoparticles. The metal oxide nanoparticles such as Fe₃O₄, TiO₂ and MoO₃ were added individually to the polymer blend (PES and SPEEK). The polymer composite membranes exhibit excellent features regarding water uptake, ion exchange capacity and proton conductivity than the pristine PES membrane. Since the presence of sulfonic acid groups provides by added SPEEK and the unique properties of inorganic nanoparticles (Fe₃O₄, TiO₂ and MoO₃) helps to interconnect the ionic domain by the absorption of more water molecules thereby enhance the conductivity value. The proton conductivity of PES, SPEEK, PES/SPEEK/Fe₃O₄, PES/SPEEK/TiO₂ and PES/SPEEK/MoO₃ membranes were 0.22 × 10^?4 S/cm, 5.18 × 10^?4 S/cm, 3.57 × 10^?4 S/cm, 4.57 × 10^?4 S/cm and 2.67 × 10^?4 S/cm respectively. Even though the blending of PES with SPEEK has reduced the conductivity value to a lesser extent, hydrophobic PES has vital role in reducing the solvent uptake, swelling ratio and improves hydrolytic stability. Glass transition temperature (T_g) of the membranes were determined from DSC thermogram and it satisfies the operating condition of fuel cell system which guarantees the thermal stability of the membrane for fuel cell application.