SPEEK Membrane Research Articles

Cross-linked sulfonated poly(ether ether ketone) membranes formed by poly(2,5-benzimidazole)-grafted graphene oxide as a novel cross-linker for direct methanol fuel cell applications

Cross-linked sulfonated poly (ether ether ketone) (C-SPEEK) membranes for direct methanol fuel cell (DMFC) applications are prepared using SPEEK with chloromethyl side groups (SPEEK-Cl) and poly (2,5-benzimidazole)-grafted graphene oxide (ABPBI-GO) as a cross-linker. The C-SPEEK membranes exhibit remarkably improved physicochemical stability and decreased methanol permeability compared to a pristine SPEEK membrane and SPEEK composite membranes composed of SPEEK and GO based fillers such as GO and ABPBI-GO. Although the proton conductivities of the C-SPEEK membranes are smaller than those of the pristine SPEEK and SPEEK composite (SPEEK/GO and SPEEK/ABPBI-GO) membranes, cell performances of the membrane electrode assemblies (MEAs) using the C-SPEEK membranes with the optimized contents of ABPBI-GO (cross-linker) are better than those using the pristine SPEEK and SPEEK composite membranes due to the well dispersion of ABPBI-GO by forming an effectively covalent bonded network structure with SPEEK-Cl resulting in the decreased methanol permeability. The maximum power density of the MEA with the C-SPEEK membrane (86 mW cm−2) is larger than those with the pristine SPEEK (71 mW cm−2) and SPEEK composite (69 mW cm−2) membranes at 60 °C with 1.5 M methanol/air feed condition.

Capacitive performance of carbon-based supercapacitors using sulfonated poly(ether ether ketone) membranes as separators: influences of casting solvents

Sulfonated poly(ether ether ketone) (SPEEK) membranes are prepared by various casting solvents. They are adopted as separators for carbon-based electrical double-layer capacitors (EDLCs). The cyclic voltammetric curves, galvanostatic charge/discharge curves, electrochemical impedance spectroscopy and cycling performance of EDLCs are evaluated. It is found that the residual solvents in SPEEK membranes have important effects on the performances of EDLCs with SPEEK membranes due to the different interactions between residual solvents and -SO3H groups of SPEEK. After SPEEK membranes are treated in 60 °C water, the EDLC with an optimum SPEEK membrane shows a specific capacitance of 37.5 F g−1 at a current density of 1 A g−1, higher than that (30 F g−1 @ 1 A g−1) of the EDLC with a porous polypropylene membrane. Furthermore, the EDLC reveals an excellent cycling stability with capacitance retention of ∼100% after 5000 cycles at a current density of 1 A g−1. These results suggest that SPEEK membranes prepared by suitable casting solvent and activation processing can serve as a class of promising compact separators for EDLCs.

Amphoteric Membranes Based on Sulfonated Polyether Ether Ketone and Imidazolium‐Functionalized Polyphenylene Oxide for Vanadium Redox Flow Battery Applications

AbstractAmphoteric membranes were obtained from imidazolium‐functionalized polyphenylene oxide (ImPPO) and sulfonated poly(ether ether ketone) (SPEEK) for an all‐vanadium redox flow battery (VRFB) application. The SPEEK/ImPPO amphoteric membranes showed a considerably lower swelling degree and water uptake compared to those of pure SPEEK membranes, owing to the formation of ionic bonds between the cationic imidazolium groups of ImPPO and the anionic sulfonate groups of SPEEK. The cationic imidazolium groups of the ImPPO exhibited a Donnan exclusion effect on vanadium ions; therefore, the amphoteric membranes showed a much lower vanadium permeability than the pure SPEEK membrane. In addition, the vanadium permeability of the amphoteric membranes deceased with an increase in the ImPPO content. SPEEK‐ImPPO20 with 20 wt% ImPPO showed a vanadium permeability of 0.43×10−9 cm2 s−1 at room temperature, which is 17 times lower than that of Nafion 212 (8×10−9 cm2 s−1). The VRFB assembled with SPEEK‐ImPPO20 showed a coulombic efficiency of 97.2 % and a voltage efficiency of 85.8 % at a current density of 60 mA cm−2, whereas the values for Nafion 212 were 92.4 % and 86.7 % under the same conditions. In addition, the VRFB assembled with SPEEK‐ImPPO20 exhibited much better capacity retention than that assembled with Nafion 212. These results indicate that the SPEEK‐ImPPO amphoteric membrane is a promising material for VRFB applications.

Molecular dynamics simulations of microstructure and transport properties of sulfonated poly-p-phenoxybenzoyl-1,4-phenylene membrane and their comparisons to sulfonated poly(ether ether ketone) membrane

Molecular simulation techniques have been used to study the microstructure and dynamic properties of sulfonated poly-p-phenoxybenzoyl-1,4-phenylene (sPPBP) membrane, and the results have been compared with those for the sulfonated poly(ether ether ketone) (sPEEK) membrane. It is shown that the phase-segregated morphology of the hydrated membranes was mostly affected by the hydration level, while the temperature had a limited effect. The sPPBP membrane had more phase segregation and higher values of proton conductivity than the sPEEK membrane. While the sPPBP membrane displayed higher H2 permeability, its conductivity in contact with diffused H2 still exceeded that of the sPEEK membrane. The results indicate that the presence of the flexible pendant side chain in the sPPBP membrane had a determining effect on its microstructure, and brought about an improvement of its dynamic properties.

The influence of ionic liquids cation on the properties of sulfonated poly (ether ether ketone)/polybenzimidazole blends applied in PEMFC

Blends modified with ionic liquid (IL) can have their conductivity improved at elevated temperatures and low relative humidity (RH) making them suitable for proton exchange membrane fuel cells (PEMFCs) applications. This study explores the synthesis and characterization of sulfonated poly (ether ether ketone)/polybenzimidazole/3-triethylammonium hydrogen sulfate (TEA-PS.HSO4) or 1-butylimidazole hydrogen sulfate (BImH.HSO4) ionic liquids blends to be applied as a novel proton exchange membranes (PEM). The oxidative stability augments with the increase of PBI content, and the membrane conductivity enhances with the increase of the IL content. Additionally, the H bond formed between the acid proton of the IL cation and the amine group of PBI avoids the IL leaching. In the PEMFC applications, the best results were obtained using the SP10/TEA5 membrane (10 and 5 wt% of PBI and TEA-PS.HSO4 respectively) at 100 °C. A high Open Circuit Potential (OCP) value was achieved (0.97 V) and an increase of 126% of the density current (1.83 A cm−2) when compared with a pure SPEEK membrane (0.81 A cm−2). These results indicate that these composite membranes have a high potential for PEMFC 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.

Non-invasive macroscopic and molecular quantification of water in Nafion® and SPEEK Proton Exchange Membranes using terahertz spectroscopy

Hydration of Proton Exchange Membranes (PEM) is vital in PEM fuel cells as it is critical in determining the overall proton conductivity. Traditional gravimetric analysis to quantify PEM's hydration is cumbersome, demands contact and importantly cannot differentiate the nature of water - bulk, bound or free water. As terahertz spectroscopy probes bulk and free water relaxations' contributions, it is an attractive non-invasive technique for studying membrane hydration dynamics - water uptake and retention. Here, THz spectroscopy measurements for hydrated Nafion® and sulphonated Polyether Ether Ketone (sPEEK) membranes in ambient atmosphere have been carried out for 100 minutes. Variation in THz absorption by the hydrated membranes with time is used for non-invasive estimation of percentage water content demonstrating good agreement with gravimetric measurements. In addition, proportion of bulk, bound and free water with time has been estimated by fitting the complex permittivity using double Debye model. Results show that % water content in hydrated sPEEK at 0th minute is 2.36 times than hydrated Nafion due to its higher porosity. Further, sPEEK has better water retention capability, especially higher bound water proportion at longer time intervals (85% more at 100th minute) than Nafion due to the presence of widely distributed small pores and comparatively stronger hydrogen bonding between the sulphonic acid and water. Thus, THz spectroscopy can be employed as an effective non-invasive tool for macroscopic and molecular quantification of water in hydrated PEMs.

Understanding of Nanophase Separation and Hydrophilic Morphology in Nafion and SPEEK Membranes: A Combined Experimental and Theoretical Studies.

The understanding of the relationship between the chemical structure and the hydrophilic structure is crucial for the designing of high-performance PEMs. Comparative studies in typical Nafion and sulfonated poly (ether ether ketone) (SPEEK) were performed using a combined experimental and theoretical method. SPEEK showed suppressed fuel crossover and good mechanical property but low water uptake, weak phase separation, and inadequate proton conductivity. Molecular dynamics (MD) simulation approaches were employed to get a molecular-level understanding of the structure–property relationship of SPEEK and Nafion membranes. In SPEEK membranes, the local aggregation of hydrophilic clusters is worse, and much stronger electrostatic interaction between Os–Hh was verified, resulting in less delocalized free H3O+ and much lower DH3O+. In addition, the probability of H2O–H3O+ association varied with water content. Particularly, SPEEK exhibited much lower H9O4+ probability at various relative water contents, leading to lower structural diffusivity than Nafion. Eventually, SPEEK possessed low vehicular and structural diffusivities, which resulted in a low proton conductivity. The results indicated that the structure of hydrated hydronium complexes would deform to adapt the confining hydrophilic channels. The confinement effect on diffusion of H2O and H3O+ is influenced by the water content and the hydrophilic morphologies. This study provided a new insight into the exploration of high-performance membranes in fuel cell.

A sulfonated PEEK/PCL composite nanofibrous membrane for periosteum tissue engineering application

The favorable mechanical property and regenerative capacity of bone graft are extremely important for the reconstruction of the large bone defect. Polyetheretherketone (PEEK) has tailored elastic modulus to natural cortical bone, while its application is limited by bio-inert surface. Tissue-engineered periosteum exhibits improved osteogenesis-inducing capacity. However, the present artificial periosteum is difficult to effectively anchor to bone grafts. The use of PEEK-based nanomembrane may be a promising candidate to integrate with PEEK bone graft without anchor problem, which has not been reported until now. In this work, a series of fluorinated PEEK polymers were successfully synthesized and electrospun into nanofibers. The chemical structure, morphology, thermal stability, wettability and mechanical strength of s-PEEK membranes were investigated. Then, a novel flexible nanocomposite membrane for tissue-engineered periosteum based on fibrous sulfonated PEEK (s-PEEK) and polycaprolactone (PCL) was prepared. The functional properties were evaluated accordingly. The s-PEEK/PCL composite membranes showed superior hydrophilic and better ductility than pure s-PEEK film. The capacity of protein adsorption was also evaluated, suggesting the elevated bioactivity of s-PEEK/PCL composite membranes. Finally, the composite membranes were successfully mineralized by a homogenous and thinner calcium phosphate layer, indicating its potential to improve the osteogenic response.

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 Ba0.9Sr0.1TiO3 (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).

High degree sulfonated poly(ether ether ketone) blend with polyvinylidene fluoride as a potential proton-conducting membrane fuel cell

Sulfonated poly(ether ether ketone) (sPEEK) membrane is a promising proton-conducting membrane for fuel cell. However, the performance and lifetime of sPEEK membrane depend on the degree of sulfonation (DS). High DS of sPEEK increases the performance, but the mechanical properties could deteriorate progressively which affect its lifetime. Thus, this study investigated the effect of adding polyvinylidene fluoride (PVDF) into high DS (80%) of sPEEK through solution blending method toward its physicochemical properties and morphology structures. The PVDF concentration was varied to 5, 10, 15, and 20 wt% relative to the sPEEK content. The existence of hydrophobic PVDF in 80% sPEEK improved the mechanical properties where the water uptake and swelling degree of membrane decreased, whereas the tensile strength increased. The sPEEK/PVDF 15 exhibited the highest proton conductivity (46.23 mS cm−1) at 80°C. Incorporating PVDF into high DS of sPEEK enhanced the mechanical properties which can be used as a proton-conducting membrane for fuel cell that may improve the performance and prolong the lifetime of the cell.

Interface engineering of mixed matrix membrane via CO2-philic polymer brush functionalized graphene oxide nanosheets for efficient gas separation

A facile method to improve CO2 separation performance of polymer is to incorporate CO2-philic particles. In this study, sulfonated polymer brush functionalized graphene oxide nanosheets (S-GO) as fillers, with sulfonated polymer brush as CO2-philic chain anchored on GO were introduced into SPEEK membrane at nanoscale level to enhance CO2 selectivity of the membrane. The S-GO enhanced the interface compatibility as shown by SEM, and the “sieve-in-a-cage” morphology in MMMs disappeared by the introduction of CO2-philic polymer brush. Benefiting from the introduction of brush at the interface, on one hand, the CO2-philic brush on S-GO helped to widen CO2 transport pathways verified by the increased radius of free volume cavity (r3) and the fractional free volume (FFV), which resulted in the increase in gas permeability. On the other hand, the addition of the polymer brush on GO increased CO2-philic sites, which imparted enhancement in the CO2 solubility selectivity. Besides, the transport of gases through the GO nanosheets created the increment in CO2 diffusion selectivity. SPEEK/S-GO MMMs showed pronounced enhancements in both CO2 permeability and CO2/CH4(N2) selectivity. Specifically, for the SPEEK/S-GO membrane doped with 8 wt% S-GO nanosheets, the CO2 permeability reached 1327 Barrer, and CO2/CH4 selectivity increased by 179% in comparison with the SPEEK control membrane, surpassing the 2008 Robeson upper bound. The distinctive virtues of polymer brush functionalized filler may be extended to fabricate a series of MMMs for efficient molecule separation.

Sulfonated poly(ether ether ketone) membrane for quinone-based organic flow batteries

Over the past few years, organic flow batteries have gained immense attention owing to their potential for large-scale energy storage applications and modifiable properties. Organic redox couples usually involve only one type of counter-ion for ion exchange membranes, and hence provide opportunities to use low-cost membranes in organic flow batteries. In this study, we prepared a sulfonated poly (ether ether ketone) (sPEEK) membrane for application in acidic flow batteries of 1,2-dihydroxybenzene-3,5-disulfonic acid/anthraquinone-2-sulfonic acid. The proton conductivity of the prepared sPEEK membrane was 50% lower than that of Nafion-212 membrane. However, the Coulombic efficiency of the sPEEK cell was similar to that of Nafion cell, and the voltage efficiency was 0.99%–2.66% higher than that of Nafion cell at different current densities. The cell using the sPEEK membrane also exhibited long-term stability, retaining 96.93% reversible capacity after 100 charge/discharge cycles at the current density of 100 mA cm−2. The results of symmetric cell cycling indicated that the decay of reversible capacity in this organic flow battery system was mainly due to the instability of organic compounds in the positive electrolyte, which was also confirmed by the self-discharge measurements of the sPEEK cell. These results demonstrate that the sPEEK membrane is highly suitable for organic flow batteries. These results will be helpful for realizing cost-effective energy storage systems.

The Effects of Sulfonated Graphene Oxides (sGO) on Ion Conductivity and Permeability of the Vanadium Redox Flow Batteries Membranes Based on Sulfonated Poly(Ether Ether Ketone) Composite

Sulfonated graphene oxide (sGO) was used as a filler to enhance performance of sulfonated poly(ether ether ketone)(sPEEK) membrane. The sGO was firstly prepared by treating graphene oxides (GO) with sulfanilic acid at 70 °C for 20 h. The sGO was characterized by FTIR and XPS techniques. Composite membranes of various amount of sGO were fabricated via solution casting method. The properties of composite membranes were investigated by measuring ion exchange capacity (IEC), water uptake, ion conductivity and vanadium ion permeability. From the results, it was found that the IEC and water uptake of the membranes increased after adding the sGO. Ion conductivity of the sPEEK membrane also increased from 8.94*10-3 Scm-1 to 10.55*10-3 Scm-1. Moreover, permeability of vanadyl sulfate (VOSO4) through the composite membranes were decreased. These composite membranes exhibit great potential for vanadium redox flow batteries application.

A comparative study of Nafion and sulfonated poly(ether ether ketone) membrane performance for iron-chromium redox flow battery

A low-cost sulfonated poly(ether ether ketone) (SPEEK) membrane with optimized degree of sulfonation (DS) has been successfully synthesized and applied in iron-chromium redox flow battery (ICRFB) in comparison with Nafion membrane. The SPEEK membrane with an optimum DS of 55% exhibits the cell performance of CE 98.53% and EE 79.13% at 80 mA cm−2 due to its longer charge retention and lower metallic ion crossover, while Nafion 115 membrane exhibits the cell performance of CE 95.97% and EE 82.33%. In addition, the SPEEK membrane demonstrates stable cell performance with slower discharge capacity decline, lower self-discharge rate, and highly stable efficiency. SPEEK membrane performs superior chemical stability in the highly oxidizing electrolytes as well, which is comparable to Nafion 115. Furthermore, the capital cost of ICRBF with SPEEK membrane occupies 5% of the overall system cost, which is 34% lower than that of ICRFB with Nafion membrane for 1 MW-8 h energy storage system.

Silica/montmorillonite nanoarchitectures and layered double hydroxide-SPEEK based composite membranes for fuel cells applications

Anionic and cationic clays were here evaluated as nanofillers of low sulfonated polyetheretherketone (SPEEK, DS = 56%) for preparation of nanocomposite electrolyte membranes for PEMFC (Proton Exchange Membrane Fuel Cells) applications. A synthetic MgAl layered double hydroxide (LDH) exchanged with sulfate anions and a porous SiO2-montmorillonite heterostructured material containing delaminated clay particles, were added to SPEEK polymer for preparation of composite membranes with different nanofiller content (3, 6 and 9%). The resulting membranes were characterized concerning their structure, morphology and electrical conductivity performance. The incorporation of the MgAl LDH and the SiO2-motmorillonite fillers into the SPEEK seems to enhance water retention and the thermal stability of the resulting composite electrolyte membranes. Moreover, the composite electrolyte membranes show higher proton conductivity than the neat SPEEK membrane (0.023 S cm−1) after incorporation of the LDH and the SiO2-motmorillonite fillers (0.070 and 0.158 S cm−1 respectively) at 120 °C and 100% relative humidity, which can be relevant for increasing the performance at high temperature of this type of membranes in fuel cell applications.

Sulfonation of blocky brominated PEEK to prepare hydrophilic-hydrophobic blocky copolymers for efficient proton conduction

Hydrophilic-hydrophobic blocky copolymers of poly(ether ether ketone) (PEEK) were prepared using a two-step post-polymerization technique. First, PEEK was brominated in the semicrystalline gel state to create a blocky BrPEEK template, which was subsequently functionalized by sulfonating the remaining runs of unfunctionalized PEEK units. The resultant degree of sulfonation of the blocky brominated, sulfonated PEEK (BrSPEEK) copolymers was inversely related to the degree of bromination, and degrees of sulfonation ranging from 26 to 71 mol% were obtained for degrees of bromination between 27 and 144 mol%. Thermal analysis using DSC and DMA revealed distinct multi-phase behavior for blocky BrSPEEK copolymers at degrees of sulfonation up to 40 mol%, suggesting phase separation between the densely brominated blocks and the sulfonated blocks into hydrophobic and hydrophilic domains, respectively. This phase separation contributed to improved dimensional stability upon swelling and enhanced proton transport at lower water content for blocky BrSPEEK membranes compared to random SPEEK membranes. Finally, morphological analysis using SAXS demonstrated that ionic aggregate size remained relatively unchanged for blocky BrSPEEK at all degrees of sulfonation, and the ionic aggregates became more closely spaced with increasing degree of sulfonation. Overall, this work demonstrates a facile, post-polymerization technique to prepare hydrophilic, hydrophobic blocky copolymers with excellent dimensional swelling and transport properties that rival those of directly polymerized block copolymers.

Bilayer Designed Hydrocarbon Membranes for All-Climate Vanadium Flow Batteries To Shield Catholyte Degradation and Mitigate Electrolyte Crossover.

The use of low-cost hydrocarbon membranes in vanadium flow batteries (VFBs) still remains a great challenge because of the strong oxidation of VO2+ catholyte and rapid capacity fading. Here, we report a bilayer design strategy using an antioxidant and dense cross-linked sulfonated polyimide (cSPI) layer as a protective layer for a sulfonated poly(ether ether ketone) (SPEEK) membrane to shield catholyte degradation and mitigate electrolyte crossover. A scalable process is developed to fabricate an integrated bilayer SPEEK/cSPI membrane without delamination by spraying a SPEEK transition layer between the two polymers. The tightly bridged cSPI layer not only protects the SPEEK membrane from degradation but also enhances its mechanical strength, puncture resistance, and proton/vanadium-ion selectivity. When assembled in a VFB, the bilayer SPEEK/cSPI membrane demonstrates excellent rate performance under current densities of 40-200 mA cm-2, high adaptability at a wide temperature range of -15 to 60 °C, very slow capacity decay rate of 0.054% per cycle at 160 mA cm-2, and a maximum power density of 480 mW cm-2. These merits make the bilayer SPEEK/cSPI membrane a promising candidate for the next-generation VFB to achieve low-cost, high-rate, and all-climate energy storage.

Sandwiching h-BN Monolayer Films between Sulfonated Poly(ether ether ketone) and Nafion for Proton Exchange Membranes with Improved Ion Selectivity.

Two-dimensional (2D) hexagonal boron nitride (h-BN) has attracted great interest due to its excellent chemical and thermal stability, electrical insulating property, high proton conductivity, and good flexibility. Integration of 2D h-BN into commercial proton exchange membranes (PEMs) has the potential to improve ion selectivity while maintaining the proton conductivity of PEMs simultaneously, which has been a longstanding challenge in membrane separation technology. Until now, such attempts are only limited in mechanically exfoliated small area h-BN and in proof-of-concept devices, due to the difficulty of growing and transferring large area uniform h-BN monolayers. Here, we develop a space-confined chemical vapor deposition approach and achieve the growth of wafer-scale uniform h-BN monolayer films on Cu rolls. We further develop a Nafion functional layer assisted transfer method which effectively transfers as-grown h-BN monolayer films from the Cu roll to sulfonated poly(ether ether ketone) (SPEEK) membrane. The as-fabricated Nafion/h-BN/SPEEK sandwich structure is used as the membrane and compared with the pure SPEEK membrane for flow batteries. Results show that the sandwich membrane exhibits ion selectivity 3-fold greater than that of a pure SPEEK membrane ( i.e., 32.1 × 104 vs 9.7 × 104 S min cm-3). In addition, we fabricate vanadium flow batteries using the Nafion/h-BN/SPEEK sandwich membrane and find that the sandwich structure does not affect the proton transport but inhibits vanadium crossover at low current density (<120 mA cm-2) due to the selective blocking of vanadium ions by 2D h-BN. As a result, the sandwich membrane exhibits a significantly improved Coulombic efficiency and energy efficiency, ∼95% and ∼91%, respectively. Our results suggest that a functional layer/2D film/target substrate-based sandwich structure shows clear potential for future 2D material-based membranes in separation technologies.

Improvement of sulfonated poly(ether ether ketone)/Y zeolite -SO3H via organo-functionalization method for direct methanol fuel cell

Sulfonated poly (ether ether ketone) (S-PEEK) and sulfonated Y zeolite (S-Y) composite membranes were prepared and characterized to be used as alternative materials for direct methanol fuel cell (DMFC). PEEK was sulfonated with a concentrated sulfuric acid at 60 °C. The degree of sulfonation was determined by the 1H NMR analysis. Organo-functionalized Y Zeolite was prepared by the silanization and graft copolymerization method using poly(2-acrylamido-2-methylpropanesulfonic acid) (pAMPS). The sulfonated Y zeolite was characterized and confirmed by FTIR and XRD. The structures of the composite membranes were characterized by SEM, TGA, and by mechanical properties. SEM results showed the uniform distributions of the sulfonated Y zeolite within the S-PEEK matrix. In this work, the existence of the sulfonated Y zeolite at various amounts (5, 10, and 15%v/v) improved the water uptake, proton conductivity, mechanical properties, methanol permeability, and oxidative stability relative to the pristine S-PEEK membrane. The proton conductivity values of the composite membranes were higher than the commercial perfluorsulfonic acid polymer namely Nafion 117 by an order of magnitude.