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.     

Dielectric behaviour of UV-crosslinked sulfonated poly (ether ether ketone) with methyl cellulose (SPEEK-MC) as proton exchange membrane

Proton exchange membrane materials based on sulfonated poly ether ether ketone (SPEEK) with Methyl Cellulose (MC) are developed by solution cast technique and exposed to UV radiation with Bezoin Ethyl Ether (BEE) as photoinitiator. The addition of MC into SPEEK polymer enhances the conductivity up to 8.7 × 10^?3 Scm^?1 at 30 °C temperature and 80% relative humidity. This new crosslinked hybrid membrane shows good prospect for the use as proton exchange membrane in fuel cell.     

Sulfonated titania submicrospheres-doped sulfonated poly(ether ether ketone) hybrid membranes with enhanced proton conductivity and reduced methanol permeability

Sulfonated titania submicrospheres (TiO₂-SO₃H) prepared through a facile chelation method are incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate organic-inorganic hybrid membranes with enhanced proton conductivity and reduced methanol permeability for potential use in direct methanol fuel cells (DMFCs). The pristine titania submicrospheres (TiO₂) with a uniform particle size are synthesized through a modified sol-gel method and sulfonated using 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt as the sulfonation reagent. The sulfonation process is confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS). The hybrid membranes are systematically characterized in terms of thermal property, mechanical property, ionic exchange capacity (IEC), swelling behavior, and microstructural features. The methanol barrier property and the proton conductivity of the SPEEK/TiO₂-SO₃H hybrid membranes are evaluated. The presence of the fillers reduces methanol crossover through the membrane. Compared with the unsulfonated TiO₂-doped membranes, the TiO₂-SO₃H-doped ones exhibit higher proton conductivity due to the additional sulfonic acid groups on the surface of TiO₂. The hybrid membrane doped with 15 wt.% TiO₂-SO₃H submicrospheres exhibits an acceptable proton conductivity of 0.053 S cm⁻¹ and a reduced methanol permeability of 4.19 × 10⁻⁷ cm² s⁻¹.     

Synergistic effect of graphene oxide and carbon nanotubes on sulfonated poly(arylene ether nitrile)-based proton conducting membranes

A strategy to prepare graphene oxide (GO)/carbon nano-tubes (CNTs)/sulfonated poly(arylene ether nitrile) (SPEN) composite membranes aimed for the proton exchange membrane is presented herein. GO and CNTs were incorporated into SPEN to improve the performances of proton exchange membrane. To study the synergistic effect of GO and CNTs, GO/SPEN and CNTs/SPEN membranes were also fabricated. The influences of GO and CNTs upon the microstructures, including thermal and mechanical properties, water uptake, swelling, proton conductivity and methanol permeability of composite membranes were investigated in detail. The membranes combining GO and CNTs could effectively avoid the self-agglomeration of GO or CNTs. In such a way, efficient proton transport channels were constructed by homogeneous dispersion of GO and CNTs within SPEN, leading to enhancement of proton conductivity. The proton conductivity of GO/CNTs/SPEN composite membrane with the ratio of 2:2 achieved the highest value of 0.1197 S/cm at 20 °C. Meanwhile, low methanol permeability (2.015 × 10^?7 cm² s^?1) was still maintained. Consequently, the combination of CNTs and GO exhibited a favorable synergistic effect on the selectivity of proton exchange membrane, which is better than pure SPEN, Nafion 117, GO/SPEN, and CNTs/SPEN membranes. This feasibility study could provide an alternative approach to design GO/CNTs-based proton-conducting membranes for DMFC applications.     

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.     

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).     

SnO2 nanoparticles dispersed carboxylated Poly(arylene ether sulfones) nanocomposites for proton exchange membrane fuel cell (PEMFC) applications

The new poly (arylene ether sulfone) (CPAEs) polymer, and carboxylated through simple Thiol Ene reaction, is characterized by FTIR, ¹H NMR. The SnO₂ nanoparticles are synthesized via alkaline and template free, one-pot hydrothermal method and characterized using HRTEM analysis. SnO₂ nanoparticles in dispersed CPAEs polymer is synthesized and examined by PXRD, SEM and TGA analyses. Further, the typical properties of bare CPAEs and 1%, 2% and 3% SnO₂ NPs of dispersed CPAEs nanocomposite membranes such as water uptake, swelling ratio, ion exchange capacity, proton conductivity and oxidative stability are evaluated. The PXRD pattern suggests the successful formation of amorphous natured CPAEs polymer and tetragonal rutile structured in SnO₂ NPs. It is observed that the SEM images indicate SnO₂ NPs, bare CPAEs polymers as spherical and form wavelike morphology. It is also noted that the HR-TEM image has identified SnO₂ NPs as non-uniform in size with an average particle size of 4 nm. 3% SnO₂ NPs loaded with CPAEs nanocomposite membrane exhibits an IEC value at 0.78 mmol/g-1 and a proton conductivity value of around 1.49 × 10^?3 S/cm^?1 at 100 °C. It shows excellent oxidative stability with a value of 12.3% degradation after being exposed to Fenton reagent at 68 °C for 8 h.     

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^®.     

Sulfonated poly(arylene ether nitrile)-based hybrid membranes containing amine-functionalized GO for constructing long-range ionic nanochannels

To simultaneously balance proton conduction and methanol diffusion, the acid-base hybrid membranes based on sulfonated poly(arylene ether nitrile) (SPEN) with 3-aminopropyltriethoxysilane functionalized graphene oxide (NGO) are prepared by solution-casting method. The loading of NGO is varied to explore the influence on cross-sectional morphology, dimensional stability, proton conductivity and methanol permeability of composite membranes. In this way, the interfacial ionic nanochannels are established at the interface of NGO and SPEN, constructing the long-range ionic nanochannels to provide fast proton transfer. Meanwhile, the formation of more zigzag transportation channels could effectively prevent methanol diffusion. The improved properties of the composite membranes can be attributed to the excellent interfacial interactions induced by acid-base and hydrogen bonding interactions. The composite membrane with 1 wt% NGO shows high proton conductivity (0.104 S·cm^?1 at 20 °C) and low methanol permeability (1.74 × 10^?7 cm²·s^?1 at 20 °C), exhibiting higher selectivity (5.977 × 10⁵ S cm^?3s) compared with pure SPEN and Nafion 117 membranes. Therefore, it will provide a feasible pathway to conquer the trade-off effect between proton conductivity and methanol resistance for direct methanol fuel cells (DMFC) applications.     

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.     

Influence of alkaline 2D carbon nitride nanosheets as fillers for anchoring HPW and improving conductivity of SPEEK nanocomposite membranes

In the present study, novel composite membranes were prepared based on sulfonated poly (ether ether ketone)/phosphotungstic acid/carbon nitride nanosheets (SPEEK/HPW/g-C₃N₄). The alkaline ultrathin g-C₃N₄ nanosheets in the membranes behaved like “double-sided adhesive”, forming hydrogen bonds with the HPW molecules to anchor hydrophilic HPW without leaking. Moreover, the amine groups of nanosheets formed acid–base pairs with –SO₃H of the SPEEK polymer matrix, facilitating the Grotthuss-type transport of proton to improve conductivity. The g-C₃N₄ inorganic particles provided tortuous pathways for methanol transport to suppress the methanol permeability coefficient. The selectivity of the SPEEK/HPW/g-C₃N₄-1.0 was 2.3 times higher than that of SPEEK/HPW and 1.5 times higher than that of pristine SPEEK. SPEEK/HPW/g-C₃N₄ hybrid membranes exhibited stable and durable operation for 240 h under 100% RH at 60 °C. Moreover, membranes exhibited superior mechanical property, with maximum elongation at break of 223.3%.     

4-Aminopyridine grafted sulfonated poly(arylene ether ketone sulfone) proton exchange membrane with high relative selectivity for fuel cells

A series of sulfonated poly(arylene ether ketone sulfone)s polymer having a degree of sulfonation of 80% and a carboxyl group in the side chain (C-SPAEKS) were prepared by polycondensation. The 4-aminopyridine grafted sulfonated poly(arylene ether ketone sulfone)s polymer membranes (SPPs) were prepared by amidation reaction with the carboxyl group to immobilize 4-aminopyridine on the side chain. The ¹H NMR results and Fourier transform infrared of SPP membranes demonstrated the successful grafting of the 4-aminopyridine. Proton conductivity, water absorption, swelling ratio, and thermal stability of different proportions of SPP membranes were investigated under the different conditions. With the increase of pyridine grafting content, the methanol permeability coefficient of the membrane decreased significantly from 8.17 × 10⁻⁷ cm²s⁻¹ to 8.92 × 10⁻⁸ cm²s⁻¹ at 25 °C. And, the proton conductivity and relative selectivity of the membrane were positively correlated with the grafted pyridine content. Among them, the SPP-4 membrane exhibited the highest proton conductivity of 0.088 Scm⁻¹ at 100 °C. The relative selectivity increased from 4.73 × 10⁴ S scm⁻³ to 9.84 × 10⁴ S scm⁻³.     

Novel proton exchange membranes based on proton conductive sulfonated PAMPS/PSSA-TiO2 hybrid nanoparticles and sulfonated poly (ether ether ketone) for PEMFC

Nanocomposite membranes based on sulfonated poly (ether ether ketone) (SPEEK) and sulfonated core-shell TiO₂ nanoparticles were prepared. TiO₂ nanoparticles were sulfonated by redox polymerization method by using sodium styrene sulfonate (SSA) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) monomers. The resultant hybrid nanoparticles (PAMPS-gTiO₂ and PSSA-g-TiO₂) were introduced to SPEEK with a sulfonation degree of 68%. Grafting of sulfonated polymers onto TiO₂ nanoparticles enhanced the content of proton transport sites in the membrane, leading to an increase in proton conductivity and power density. Besides, the mechanical and dimensional stabilities of the nanocomposite membranes were also improved compared with pure SPEEK membrane. The maximum power density for membranes containing 7.5 wt% of PAMPS-gTiO₂ and PSSA-g-TiO₂ nanoparticles at 80 °C obtained 283 mW cm⁻² and 245 mW cm⁻², respectively.     

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.     

Influence of mesoporous phosphotungstic acid on the physicochemical properties and performance of sulfonated poly ether ether ketone in proton exchange membrane fuel cell

This study demonstrates the successful development of hybrid mesoporous siliceous phosphotungstic acid (mPTA-Si) and sulfonated poly ether ether ketone (SPEEK) as a proton exchange membrane with a high performance in hydrogen proton exchange membrane fuel cells (PEMFC). SPEEK acts as a polymeric membrane matrix and mPTA-Si acts as the mechanical reinforcer and proton conducting enhancer. Interestingly, incorporating mPTA-Si did not affect the morphological aspect of SPEEK as dense membrane upon loading the amount of mPTA-Si up to 2.5 wt%. The water uptake reduced to 14% from 21.5% when mPTA-Si content increases from 0.5 to 2.5 wt% respectively. Meanwhile, the proton conductivity increased to 0.01 Scm^?1 with 1.0 wt% mPTA-Si and maximum power density of 180.87 mWcm^?2 which is 200% improvement as compared to pristine SPEEK membrane. The systematic study of hybrid SP-mPTA-Si membrane proved a substantial enhancement in the performance together with further improvement on physicochemical properties of parent SPEEK membrane desirable for the PEMFC application.     

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.     

Novel modification method to prepare crosslinked sulfonated poly(ether ether ketone)/silica hybrid membranes for fuel cells

Crosslinked organic-inorganic hybrid membranes are prepared from hydroxyl-functionalized sulfonated poly(ether ether ketone) (SPEEK) and various amounts of silica with the aims to improve dimensional stability and methanol resistance. The partially hydroxyl-functionalized SPEEK is prepared by the reduction of some benzophenone moieties of SPEEK into the corresponding benzhydrol moieties which is then reacted with (3-isocyanatopropyl)triethoxysilane (ICPTES) to get a side chained polymer bearing triethoxysilyl groups. These groups are subsequently co-hydrolyzed with tetraethoxysilane (TEOS) and allow the membrane to form a crosslinked network via a sol-gel process. The obtained hybrid membranes with covalent bonds between organic and inorganic phases exhibit much lower methanol swelling ratio and water uptake. With the increase of silica content, the methanol permeability coefficient of the hybrid membranes decreases at first and then increased. At silica content of about 6 wt.%, the methanol permeability coefficient reaches a minimum of 7.15 × 10⁻⁷ cm² s⁻¹, a 5-fold decrease compared with that of the pristine SPEEK. Despite the fact that the proton conductivity is decreased to some extent as a result of introduction of the silica, the hybrid membranes with silica content of 4-8 wt.% shows higher selectivity than Nafion117.     

Improved proton conduction of sulfonated poly (ether ether ketone) membrane by sulfonated covalent organic framework nanosheets

A type of sulfonated covalent organic framework nanosheets (TpPa-SO₃H) was synthesized via interfacial polymerization and incorporated into sulfonated poly (ether ether ketone) (SPEEK) matrix to prepare proton exchange membranes (PEMs). The densely and orderly arranged sulfonic acid groups in the rigid skeleton of the TpPa-SO₃H nanosheets, together with their high-aspect-ratio and well-defined porous structure provide proton-conducting highways in the membrane. The doping of TpPa-SO₃H nanosheets led to an increased ion exchange capacity up to 2.34 mmol g^?1 but a 2-folds reduced swelling ratio, remarkably mitigating the trade-off between high IEC and excessive swelling ratio. Based on the high IEC and orderly arranged proton-conducting sites, the SPEEK/TpPa–SO₃H–5 membrane exhibited the maximum proton conductivity of 0.346 S cm^?1 at 80 °C, 1.91-folds higher than the pristine SPEEK membrane. The mechanical strength of the composite membrane was also improved by 2.05-folds–74.5 MPa. The single H₂/O₂ fuel cell using the SPEEK/TpPa–SO₃H–5 membrane presented favorable performance with an open voltage of 1.01 V and a power density of 86.54 mW cm^?2.     

In-situ molecular-level hybridization enabling high-sulfonation-degree sulfonated poly(ether ether ketone) membrane with excellent anti-swelling ability and proton conduction

Sulfonated poly(ether ether ketone) (SPEEK) membrane with high sulfonation degree (SD) is a promising substitute of Nafion as proton exchange membrane (PEM), due to the excellent proton conductivity and low cost. However, its widespread application is limited by the inferior structural stability. Here, we report the fabrication of high SD SPEEK membrane with outstanding structural stability through an in-situ molecular-level hybridization method. Concretely, the ionic nanophase of SPEEK membrane is filled with precursors, which are then in-situ converted into polymer quantum dots (PQDs) by a microwave-assisted polycondensation process. In this manner, the micro-phase separation structure of SPEEK membrane is well maintained. PQDs with abundant hydrophilic functional groups together with the inherent –SO₃H groups impart hybrid membrane highly enhanced proton conductivity of 138.2 mS cm⁻¹ at 80 °C, which is comparable to Nafion. This then offers a 116.3% enhancement in device output power. Meanwhile, PQDs act as cross-linkers via generated electrostatic interactions with SPEEK, affording hybrid membrane with SD of 94.1% an ultralow swelling ratio of 1.35% at 25 °C, about 35 times lower than control membrane. More importantly, the in-situ molecular-level hybridization method is versatile, which can also boost the performances of chitosan (CS)-based membranes.     

Synthesis and electrochemical properties of blend membranes of polysulfone and poly (acrylic acid-co-2-(2-(piperazin-1-yl) ethylamino)-2-hydroxyethyl methacrylate) for proton exchange membrane fuel cell

In this work, new piperazine containing copolymer membrane was developed from acrylic acid and 2-(2-(piperazin-1-yl)ethylamino)-2-hydroxyethyl methacrylate through free radical polymerization method by means of AIBN as an initiator, in bulk. The monomer feed ratio was varied to obtain various copolymers having a different composition. The developed copolymer was blended in polysulfone (PSF) at 3 and 6 wt% using N,N′-Dimethylformamide solvent. The FTIR spectra and 1H NMR spectral data have proved the presence of copolymer that has hydrophilic functional group which influences the better proton conductivity. The membranes were characterized by their morphology using scanning electron microscope and x-ray diffraction analysis. The hydrophilic nature of the membranes is proved through high water uptake ratio. The exchangeable proton at the carboxylic acid group has enhanced the high ion exchange capacity. The blend membranes have higher water uptake, low swelling rate and higher ion exchange capacity than that of neat PSF membrane. The fabrication of fuel cell and studies on proton exchange capacity indicates that the prepared membranes have proton conductivity of as high as 8.77 × 10^?4 S cm^?1. Low methanol crossover was obtained about 2.112 × 10^?6 cm²s^?1 when compared to the pristine membrane.