Sulfonated Polyether Ether Ketone Membrane Research Articles

Anchoring of Fe-MIL-101-NH2 to the Polymer Membrane Matrix through the Hinsberg Reaction to Promote Conductivity of SPEEK Membranes.

SCPEEK@MOF proton exchange membranes, where SCPEEK is sulfinyl chloride polyether ether ketone and MOF is a metal-organic framework, were prepared by doping Fe-MIL-101-NH2 into polymers. The amino group in the MOF and the -SOCl2 group in thionyl chloride polyether ether ketone cross-link to form a covalent bond through the Hinsberg reaction, and the prepared composite membrane has stronger stability than other electrostatic interactions and simple physical doping composite membranes. The formation of covalent bonds improves the water absorption of the composite membrane, which makes it easy for water molecules to form hydrogen bonds. Moreover, SPEEK as a proton conductive polymer and the synergy of MOFs improve the proton conductivity of composite membranes. The composite membranes were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The swelling rate, water absorption, mechanical stability, ion exchange capacity, and proton conductivity of the pure sulfonated polyether ether ketone (SPEEK) membrane were compared with those of the mechanically doped SPEEK/MOF membrane and the composite membrane SCPEEK@MOF doped with different ratios of Fe-MIL-101-NH2, and all of the SCPEEK@MOF showed superior performance. When the Fe-MIL-101-NH2 loading rate of the composite membrane is 2%, the proton conductivity of the composite membrane can reach 0.202 S cm-1 at 363 K and a 98% relative humidity, which is much higher than that of the SPEEK/MOF membrane obtained by simple physical doping under the same conditions.

Development of Aqueous Organic Flow Battery Using SPEEK Membrane and Eco-Friendly Electrolytes

Aqueous organic redox flow batteries (AORFBs) are a type of flow battery that offers a promising solution for energy storage, and one of the main issues is selecting low-cost membranes with high ion conductivity to enhance performance and efficiency. In this study, low-cost sulfonated poly ether ether ketone (SPEEK) membranes were fabricated using the casting method, with the polymer/solvent ratios of SPEEK and N,N'-dimethylformamide (DMF) being varied. The Nafion 117 membrane was used as a benchmark for comparison. The performance of aqueous organic redox flow batteries employing anthraquinone-2-sulfonic acid (AQS) and 1,2-benzoquinone-3,5-disulfonic acid (BQDS) as electrolytes was evaluated. The SPEEK membranes were determined to have dense, homogeneous surfaces with no flaws and a thickness of 60 microns. In addition, their physicochemical properties, such as water uptake, swelling ratio, ion exchange capacity, and degree of sulfonation, were investigated. The results showed that the SPEEK membranes had better rate performance and cycle stability when compared to the Nafion117 membrane during charge-discharge cycles. Additionally, the SPEEK membranes exhibited slower potential drops and higher power density during constant current mode operation, despite showing no significant differences in energy efficiency and power density. These findings demonstrate the potential of SPEEK membranes for use in AORFBs and as a benchmark for future research and development.

Review of SPEEK Amphoteric Proton Exchange Membranes in All Vanadium Flow Batteries

Sulfonated polyether ether ketone (SPEEK) membranes have been widely used in the field of all vanadium flow batteries (VFRB) due to their simple structure, convenient preparation, good thermal and mechanical stability, low cost, and easy modification. However, its membrane performance largely depends on the degree of sulfonation. As the degree of sulfonation increases, the proton conductivity increases, but it also increases water uptake, leading to excessive swelling and vanadium ion penetration, thereby reducing the stability of the membrane and the performance of the battery. The introduction of alkaline functional groups can serve as proton acceptors to promote proton transport through the Grotthus mechanism, and on the other hand, they can form acid-base pairs with sulfonic acid groups. The resulting hydrogen bonds, acid-base interactions, ion bonds, and other interface interactions are beneficial for reducing the swelling rate of SPEEK membranes, and can also adjust the size of proton transport channels, constructing efficient proton transport channels that are both conducive to proton transport and can hinder the passage of vanadium ions, Improve the ion selectivity of membranes. Therefore, this article reviews the basic research and practical development status of SPEEK amphoteric membranes in VRFB, including the latest progress in various modification strategies. And evaluated the challenges and potential future research directions faced by the development of SPEEK membranes.

Construction of thermal, chemical and mechanically stable ion exchange membranes with improved ion selectivity for vanadium redox flow batteries applications

As an alternative to expensive Nafion membrane, SPEEK (Sulfonated Poly Ether Ether Ketone) membrane reinforced with hydroxylated boron nitride is investigated as a potential proton exchange membrane for vanadium redox flow battery (VRFB). SPEEK based hybrid membranes are characterized for their thermal, mechanical and chemical stability along with proton conductivity and vanadium permeability. The results reveal that the hydroxylated boron nitride enhances the physicochemical properties of SPEEK and shown to improve selectivity of ions (52.629 *103. S.cm−3.min) with better stability. The improved properties are attributed to hydrogen bond formation between hydroxyl moieties of born nitride and sulfonic acid group in SPEEK. Among the hybrid membrane, SPEEK reinforced with 0.05 wt % of hydroxylated boron nitride exhibits a higher coulombic efficiency of 93.6 % (91.8 % for Nafion), higher self-discharge time of 14.21 h (11.36 h for Nafion) in VRFB single cell performance study. Cyclic performance study in VRFB with hybrid membrane shows stable characteristics during 50 cycles and it reaffirms the structural, thermal and chemical stability of hybrid membranes. Thus, this study provides insight into replacing commercial Nafion with hydroxylated boron nitride reinforced SPEEK hybrid membrane for vanadium redox flow battery.

Cost estimation and performance evaluation of 3D printed membranes for vanadium redox flow batteries

AbstractThe membrane is a central component in the commercialization of vanadium redox flow batteries (VRFB), with Nafion being the preferred material for those membranes. Nafion suffers however from high vanadium crossover and high cost, thus limiting its wider commercial application in VRFB. To address this, studies have focused on sulfonated polyether ether ketone (SPEEK) as an alternative material. This work presents an economic study on the production costs of 3D printed SPEEK (3D‐SPEEK) membranes for VRFB, with multiple production scenarios evaluated. This analysis relies on the performances of 3D‐SPEEK membranes prepared in our laboratory, which have shown higher Coulombic efficiency and lower vanadium ions diffusion than Nafion membranes. Results from the economic analysis revealed that the cost of the 3D‐SPEEK membrane varies from 567.77 to 79.35 €/m2 depending on the production scheme and scale used. Production costs lower than commercial Nafion membranes are achieved when a large production scheme is used. Further analysis shows that 3D‐SPEEK membranes might even be cheaper than conventional SPEEK membranes if their printing time is reduced.

In Situ-Doped Sulfonated Schiff-Base Networks in SPEEK Composite Membranes with Enhanced Proton Conductivity.

Sulfonated polyether ether ketone (SPEEK) has been widely investigated in proton exchange membrane fuel cells (PEMFCs) due to its excellent thermal stability, chemical stability, and low cost compared with Nafion. However, excessive degree of sulfonation will easily lead to the decrease in thermal stabilities and mechanical properties of SPEEK membranes, which limits the enhancement of proton conductivity. In this work, a series of Schiff-base networks (SNWs) with different contents are in situ synthesized in the SPEEK membrane by a Schiff-base co-condensation reaction, and then, the composite membranes are soaked in sulfonic acid for further improvement of proton conductivity. The highest doping amount of the SNW filler in SPEEK can reach 20 wt %. High loading and low leaching rate of H2SO4 are easily achieved owing to the similar size between sulfuric acid molecules and micropores in SNW. Moreover, abundant amino and imine groups in SNW networks contribute to the anchoring of H2SO4 into the pores by acid-base interactions. The proton conductivity of the SPEEK/S-SNW-15 composite membrane can reach 115.53 mS cm-1 at 80 °C and 100% RH. Meanwhile, the composite membrane also exhibits satisfied stability and mechanical property.

Surface modification, counter-ion exchange effect on thermally annealed sulfonated poly (ether ether ketone) membranes for vanadium redox flow battery

In this work, we report new approaches to sulfonated poly ether ether ketone (SPEEK) membranes to improve its inhibition to vanadium ions along with polymer reinforcement. First approach includes facile thermal annealing of SPEEK membrane (SPEEK-T) which could reinforce the polymer matrix. Second approach was to exchange the labile proton of SPEEK with benzimidazole to protect the hydrolytic decomposition of sulfonic acid followed by thermal annealing (SPEEK-Benz), and third approach focused on creating barrier layer for vanadium ions by coating polyethyleneimine on SPEEK membrane followed by thermal treatment (SPEEK-PEI). The chemical stability study of the membranes revealed acceptable dimension change and VO2+ electrolyte sorption for all the membranes with least dimension change and weight gain of 5 % and 12 %, respectively, for SPEEK-PEI. Amongst four prepared membranes, SPEEK-PEI membrane displayed least diffusion coefficient of 8.04 × 10−7, 8.94 × 10−7, 4.20 × 10−7 cm2 min−1 for V3+, VO2+, and VO2+ ions respectively. VRFB assembled with SPEEK-PEI resulted highest Coulombic efficiency (CE) of 97 % and energy efficiency (EE) of 66 % over 50 charge/discharge cycles at 100 mA cm−2. Peak power density of 255, 248, 240 and 235 mW cm−2 at current density of 300 mA cm−2 was observed for SPEEK-PEI, SPEEK-Benz, SPEEK-T, and SPEEK-48, respectively; these values were higher than 225 mW cm−2 for Nafion®117 in identical experimental conditions. The excellent VRFB performance suggest that the developed new approaches have pronounced effect on the membrane properties and can be further improved to obtain an ideal VRFB separator. Furthermore, the surface modification approaches adopted in this work is facile, reproducible and scalable and can be further designed to develop high performance ion exchange membranes for separation/purification and energy.

Sulfonated polyether ether ketone composite proton exchange membranes incorporated with a novel hierarchical‐structure hybrid nanofiller consisting solid superacid zirconium phosphate and CNTs

AbstractHow to simultaneously improved the proton conductivity and mechanical strength is a key problem facing currently used proton exchange membranes (PEMs). Herein, a solid inorganic superacid‐zirconium phosphate (ZrP) with a two‐dimensional layer structure was combined with one‐dimensional carbon nanotubes (CNTs) to prepare hybrid nanofiller ZrP‐CNTs by an in situ chemical deposition method. The new hybrid nanofiller was then applied to modify sulfonated polyether ether ketone (SPEEK), a widely used PEM matrix, to obtain a series of composite membranes. The structure and properties of the membranes were fully characterized by SEM, XRD, FTIR, TG, tensile properties, and proton conductivity. The results showed that the proton conductivities of the membranes were significantly improved due to the addition of super solid acid‐ZrP that has abundant proton sources or proton sites. Moreover, the composite membranes exhibited better mechanical properties and thermal stability than those of pure SPEEK membrane, owing to the great interface interaction and good compatibility between ZrP‐CNTs and SPEEK. The composite membrane (2 wt% ZrP‐CNTs) demonstrated the optimal comprehensive performance. Its proton conductivity was 36.63 mS cm−1 and its tensile strength was 37.56 MPa, which was 70% and 10%, respectively, higher than those of the pure SPEEK membrane under the same condition.

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.

Modification of sulfonated poly (etherether ketone) composite polymer electrolyte membranes with 2D molybdenum disulfide nanosheet-coated carbon nanotubes for direct methanol fuel cell application

Fabrication of novel proton exchange membrane (PEM) is crucial to the development of direct methanol fuel cells (DMFCs). Here, molybdenum disulfide (MoS2) nanosheets were anchored onto carbon nanotubes (CNTs) via a facile in-situ growth method, and then a series of composite PEMs were fabricated via embedding MoS2-coated CNTs (MoS2@CNTs) in the sulfonated polyether ether ketone (SPEEK) matrix. The coating of MoS2 nanosheets improved the dispersibility and compatibility with the polymer matrix and enhanced the mechanical properties of the composite membranes. Owing to the unique one-dimensional structure of CNTs and the hydrophilic MoS2 coating, channel-like ion transport pathways (water channels) could be constructed, which would enhance the ionic conductivity of the composite membrane. It is worth noting that the incorporation of 1 wt% MoS2@CNTs at 80 °C resulted in 1.7-fold proton conductivity relative to pristine SPEEK membrane, and substantially decreased its methanol permeability. As a result, the SPEEK/MoS2-1 composite membrane exhibited excellent fuel cell performance with a high peak power density of 98.5 mW cm−2 at 70 °C, which was 73.7% higher than that of the SPEEK membrane and Nafion-115 membrane. Finally, the durability test further validated the potential of SPEEK/MoS2@CNTs composite membrane to be used as an alternative for Nafion membrane.

Fabrication of a cost-effective cation exchange membrane for advanced energy storage in a decoupled alkaline-neutral electrolyte system

Herein, a cost-effective cation exchange membrane (CEM), sulfonated polyether ether ketone membrane (SPEEK-M), is prepared through heat sulfuric acid treatment followed by evaporation induced thermal phase separation. Negative charged sulfonic acid functional groups can be grafted on the polymer chains during this process. Exchange of cations, and repulsion of anions are hence realized using this membrane. To further improve the performance of the SPEEK-M, SiO2 is introduced in. It is found that ionic conductivity is increased to 46.79 mS·cm−1 for the SiO2-SPEEK-M from 19.17 mS·cm−1 for the SPEEK-M. Compared with commercial CEMs, such as DuPont N117 and Huamotech, volume expansion of the SPEEK-M is rather small after immersed in water. The membranes are then used as separators in Zn-ion hybrid capacitors (ZIHCs) with decoupled aqueous electrolytes, which includes a Zn foil anode in an alkaline electrolyte, and an activated carbon (AC) cathode in a neutral electrolyte. The electrolyte decoupling strategy maximizes the operating window of this system to 0.5 ∼ 2.2 V. The specific capacity of the AC can reach 390.0C·g−1 at a current density of 0.5 A·g−1. An energy density of 46.2 Wh·kg−1 at a power density of 3416.1 W·kg−1 can be achieved (counting the weight of AC). After gelation of the electrolytes, the growth of Zn dendrite is successfully eliminated, and capacity retention along cycling is increased to 94.3 % using the SiO2-SPEEK-M, which is better than that using the commercial DuPont N117 and Huamotech. The raw materials used here to prepare the CEMs are cheap and eco-friendly, which makes the membranes promising candidates as separators for decoupled electrolyte systems.

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. • Incorporation of porous HPA in SPEEK membrane used as electrolyte layer in PEMFC. • Physical and chemical properties are being characterized to get the best membrane. • The performance analysis concluded the highest performing membrane.

Enhanced performance of novel carbon nanotubes - sulfonated poly ether ether ketone (speek) composite proton exchange membrane in mfc application

Sulfonated poly ether ether ketone (SPEEK) nanocomposite proton exchange membrane (PEM) was prepared by incorporating multi-walled carbon nanotubes (CNT) at different weight percentages for microbial fuel cell (MFC) applications. Physico-chemical, thermal, mechanical and morphological characteristics of the prepared CNT-SPEEK composite membranes were analyzed using various techniques. Further, the water uptake capacity, Ion exchange capacity (IEC) and MFC performance of the CNT-SPEEK composite membranes were evaluated and compared with the pristine SPEEK membrane. Results show that incorporation of CNTs in SPEEK membranes exhibited a better water uptake capacity (34.18%–36.02%) and IEC (1.94–2.15 meq/g) compared to the SPEEK membrane. Improvement in membrane properties resulted in 2-fold higher power density compared to SPEEK membrane. Composite membrane with 0.75% CNT-SPEEK produced the higher power density (1.77 W/m2) in comparison with all the membranes evaluated. Chemical oxygen demand (COD) removal efficiency values of the MFC with SPEEK composite membranes were also found to be around 90%. Overall, the results reveal that CNT-SPEEK composite membrane as a potential PEM for MFC applications.

Functionalized carbon black modified sulfonated polyether ether ketone membrane for highly stable vanadium redox flow battery

Sulfonated polyether ether ketone (SPEEK) membranes have attracted much attention as ion exchange membranes for vanadium redox flow batteries (VRFBs) owing to their affordability and low vanadium permeability. It's noted that they suffer from poor proton conductivity at low degree of sulfonation (DS) while poor mechanical stability at high DS. Therefore, it is a challenge to balance their performance and DS. In this work, functionalized carbon black (FCB) particles with sulfonic acid substituents were prepared and used as fillers to obtain advanced SPEEK composite membranes. This kind of SPEEK/FCB composite membranes show outstanding ion selectivity, low vanadium permeability, high proton conductivity and excellent stability. The VRFB cell with the optimized SPEEK/FCB composite membrane shows high energy efficiency (94.26%, at 50 mA cm−2), low-capacity fade rate (0.052% per cycle, at 120 mA cm−2) and long cycle life.

An overview on the progress and development of modified sulfonated polyether ether ketone membranes for vanadium redox flow battery applications

Vanadium redox flow batteries (VRFB) are among the most promising approaches to efficiently store renewable energies. In such battery type, Nafion is commonly used as membrane material but suffers from high vanadium crossover and cost. These drawbacks negatively influence the widespread commercial application of VRFBs. Alternative membrane materials with high performance and low cost are thus being developed to address these shortfalls. Among those, possible materials for the VRFB membrane is sulfonated polyether ether ketone (SPEEK), which recently attracted considerable attention due to its low cost, combined with mechanical and chemical stability, and ease of preparation. This review summarizes the research activities related to the development of SPEEK-based membranes for VRFB applications and gives an overview of the properties of PEEK and its sulfonated form. A critical analysis on the challenges of SPEEK-based membranes is also discussed.

Mesoscale Simulation on the Hydrated Morphologies of SPEEK Membrane

AbstractProton transport in proton exchange membrane is considered to depend on the hydrophilic domain formed by the microphase separation between hydrophobic and hydrophilic segments of the membrane. Therefore, the study of hydrated morphologies is crucial to understand proton transport. Here, the mesoscopic structure of sulfonated polyether ether ketone (SPEEK) membrane and SPEEK/polyethersulfone (PES) blend membrane is investigated by dissipative particle dynamics (DPD) simulation. The degree of sulfonation, water content, and PES content are considered to affect proton transport. Results show that the hydrophilic particles combine with water and are separated from hydrophobic particles to form clusters of different sizes. For the SPEEK membrane, with the increase in the sulfonation degree, clusters become large and begin to connect. Compared with isolated clusters at low water content, water clusters become large with increased water content. When water content λ = 16, the cluster size is the largest. The addition of PES accelerates the phase separation in the membrane and increases the size of water clusters. When SPEEK/PES = 4:6, the cluster size is the largest and provides the best proton transport pathway.

Sulfonated poly ether ether ketone (SPEEK) based composite cation exchange membranes for salt removal from brackish water

Availability of fresh water is a serious concern due water pollution in these days. Several efforts have been made for water desalination where membrane based technology is considered prominently. Here, we synthesised sulfonated poly ether ether ketone (SPEEK) based functionalized hexagonal boron nitride (SBN) composite cation exchange membranes for water desalination. The morphology of BN and presence of sulfonic acid group are confirmed by TEM analysis. Ionic conductivity for SPEEK membrane is found to be 2.02 × 10−2 S. cm−1, which reaches to 4.05 × 10−2 S. cm−1 for SBN-10/SPEEK composite membrane. Ion exchange capacity of the SBN-10/SPEEK composite membrane also increased by 40 % and reaches to 1.66 meq.g-1 as compared to SPEEK membrane. Incorporation of SBN in membrane matrix not only improve the ion exchange capacity and ionic conductivity as well as expand the stability of the membranes. SEM micrograph confirm the uniform distribution of SBN in SPEEK membrane matrix. The composite membranes show the better ion transport properties in term of current efficiency and power consumption during salt removal from brackish water by electrodialysis. For SBN-10/SPEEK composite membrane power consumption was 0.75 kW h.Kg-1 with 98.5 % current efficiency.

Improved performance of sulfonated poly ether ether ketone/three-dimensional hierarchical molybdenum disulfide nanoflower composite proton exchange membrane for fuel cells

As one of the most essential components of fuel cells, the commercialized Nafion-based proton exchange membranes(PEMs) suffer from several drawbacks like high cost and methanol permeability. The aim of this work is to fabricate a high performance PEM with combined low cost and methanol permeability together with high proton conductivity. Three-dimensional hierarchical molybdenum disulfide (MoS2) nanoflower is synthesized via a facile one-pot hydrothermal method, and then was embedd into sulfonated poly ether ether ketone (SPEEK) matrix to prepare composite PEM. The three-dimensional hierarchical architectures of MoS2 nanoflower can not only avoid the aggregation of MoS2 nanosheets but also provide abundant surface area and active sites, which are of benefit to fully take advantage of the intrinsic water absorption and methanol diffusion resistance ability of MoS2 nanosheets. The formed hydrogen bond network with water passway contributes to the improvement in proton conduction of composite membrane. As a consequence, composite membrane with 1 wt% MoS2 nanoflower loading content achieves optimized proton conductivity (0.123 S cm−1, 80 °C) and methanol permeability (21.5 × 10–7 cm2 s−1, 70 °C), which is 59.7% higher and 79.1% lower than that of SPEEK control membrane. Owing to increased proton conductivity and decreased methanol permeability, the maximum power density of the SPEEK/MoS2-1 composite membrane is 82.7 mW cm−2 at 70 °C, which is nearly 64.7% higher than that of pure SPEEK membrane (only 50.2 mW cm−2). Furthermore, the durability test confirms that the SPEEK/MoS2 composite membrane still possesses satisfactory stability even after continuous operation at 70 °C for 100 h.

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

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

Performance of the sulfonated poly ether ether ketone proton exchange membrane modified with sulfonated polystyrene and phosphotungstic acid for microbial fuel cell applications

AbstractIn this research, the preparation of low cost proton exchange membranes (PEMs) based on sulfonated poly ether ether ketone (SPEEK) for application in the microbial fuel cells (MFCs) is studied. Sulfonated polystyrene (SPS) and phosphotungstic acid (PWA) were employed to improve the performance of PEM through the creation of more proton pathways. At first, the sulfonation of PEEK and polystyrene were performed through two modified methods to obtain uniform and high degree of sulfonation (DS) of the polymers and then, the PEMs were prepared through the solution casting method. Accordingly, the formation of uniform skin layer was confirmed by the SEM micrographs. Blending the aforementioned additives to the SPEEK polymer solution significantly enhanced the proton conductivity, water uptake and durability of the modified membranes. The proton conductivities of SPEEK/SPS and SPEEK/PWA membranes at additive/SPEEK weight ratio of 0.15 were 45.3% and 26.2% higher than that of the commercial Nafion117 membrane, respectively. Moreover, the degradation times for the abovementioned modified membranes were 140 and 350 min which indicated satisfactory oxidation stability. Besides, the aforementioned membranes exhibited two times more water uptake compared to the neat SPEEK membrane. Finally, SPEEK/SPS and SPEEK/PWA membranes produced 68% and 36% higher maximum power in the MFC, compared to the commercial Nafion117 membrane. Therefore, the fabricated PEMs are potentially suitable alternatives to be used in the fuel cell applications.