High Degree Of Sulfonation Research Articles

Imidazolium-Based Sulfonating Agent to Control the Degree of Sulfonation of Aromatic Polymers and Enable Plastics-to-Electronics Upgrading.

The accumulation of plastic waste in the environment is a growing environmental, economic, and societal challenge. Plastic upgrading, the conversion of low-value polymers to high-value materials, could address this challenge. Among upgrading strategies, the sulfonation of aromatic polymers is a powerful approach to access high-value materials for a range of applications, such as ion-exchange resins and membranes, electronic materials, and pharmaceuticals. While many sulfonation methods have been reported, achieving high degrees of sulfonation while minimizing side reactions that lead to defects in the polymer chains remains challenging. Additionally, sulfonating agents are most often used in large excess, which prevents precise control over the degree of sulfonation of aromatic polymers and their functionality. Herein, we address these challenges using 1,3-disulfonic acid imidazolium chloride ([Dsim]Cl), a sulfonic acid-based ionic liquid, to sulfonate aromatic polymers and upgrade plastic waste to electronic materials. We show that stoichiometric [Dsim]Cl can effectively sulfonate model polystyrene up to 92% in high yields, with minimal defects and high regioselectivity for the para position. Owing to its high reactivity, the use of substoichiometric [Dsim]Cl uniquely allows for precise control over the degree of sulfonation of polystyrene. This approach is also applicable to a wide range of aromatic polymers, including waste plastic. To prove the utility of our approach, samples of poly(styrene sulfonate) (PSS), obtained from either partially sulfonated polystyrene or expanded polystyrene waste, are used as scaffolds for poly(3,4-ethylenedioxythiophene) (PEDOT) to form the ubiquitous conductive material PEDOT:PSS. PEDOT:PSS from plastic waste is subsequently integrated into organic electrochemical transistors (OECTs) or as a hole transport layer (HTL) in a hybrid solar cell and shows the same performance as commercial PEDOT:PSS. This imidazolium-mediated approach to precisely sulfonating aromatic polymers provides a pathway toward upgrading postconsumer plastic waste to high-value electronic materials.

Polysulfone with Different Degrees of Sulfonation: Simple Method with Acetyl Sulfate

In this work, the authors present as an innovation, the homogeneous sulfonation of Udel® polysulfone (PSU) with acetylsulfate (ACS) under reflux at 45°C in dichloromethane and inert N2 atmosphere (g) for 1.5 h. Different proportions of ACS were used, obtaining sulfonated products with varying degrees of sulfonation (DS). Confirmation of sulfonated polysulfone (PSU-S), denominated as PSU-SA (high degree of sulfonation) and PSU-SB (low degree of sulfonation), was carried out by FTIR and 1H NMR. Determination of DS was carried out through thermogravimetric analysis (TGA/DSC), varying indexes between 0.883 and 3.022, which correspond to a sulfonated polymer with ion exchange capacity (IEC) from 1.720 to 4.400 meq/g. The evolution of DS related to methods used was monitored and confirmed by 1H NRM. Sulfonation is undertaken to enhance the suitability of this polymer for future applications in the production of biofuels, targeting its utilization in catalytic processes for esterification and transesterification mechanisms of oils and fats.

SPEEK-co-PEK-x proton exchange membranes with controllable sulfonation degree for proton exchange membrane fuel cells

Sulfonated poly(ether ether ketone)-poly(ether ketone) (SPEEK-co-PEK-x) copolymers with controlled degree of sulfonation are synthesized by the polycondensation reaction of varying monomer ratios. Compared with the traditional homopolymer sulfonated poly(ether ether ketone) (H-SPEEK), the SPEEK-co-PEK-x copolymer membrane has a high degree of sulfonation and excellent proton conductivity. Meanwhile, it also has favorable mechanical properties and stability. This is attributed to the introduction of the -PEK- segment. The SPEEK-co-PEK-75 membrane exhibits the highest conductivity (0.285 S cm−1) at 80 °C, 100% RH and when tests at 80 °C with 80% RH, the SPEEK-co-PEK-75 membrane reaches 0.0587 S cm−1. In addition, the tensile strength of the SPEEK-co-PEK-75 membrane reaches 47.66 MPa at room temperature. Moreover, the study investigates the impact of key variables on the single-cell performance of SPEEK-co-PEK-x membranes. The measured peak power densities of the SPEEK-co-PEK-75 membrane are 212 mW cm−2 and 495 mW cm−2 at 70% RH and 100% RH, which are 1.3 times and 1.7 times higher than that of the Nafion 117 membrane, respectively. After the 80 h durability test at 80 °C and 80% RH, the voltage of the SPEEK-co-PEK-75 membrane only drops by 4.8%. The presence of the -PEK- segment results in a more compact and connected distribution of hydrophilic ion clusters in the SPEEK-co-PEK-X membrane. This adjustment greatly enhances the performance of the membrane, making it an excellent candidate for proton exchange membrane in H2/air fuel cells.

Construction of high performance sulfonated aromatic block copolymer/PTFE composite membrane for pervaporation desalination

Pervaporation (PV) has great prospect in desalination of hypersaline water and its application is still limited by lack of high performance membrane with high water flux and good sustainability. This study reported a method of constructing thin film composite (TFC) membrane consisting of sulfonated aromatic polymer (SAP) active layer and porous PTFE substrate for PV desalination. The TFC membrane was fabricated by hydrophilic modification of PTFE support, followed by coating polystyrene-grafted SEBS on the support and post-sulfonation. The modification of PTFE by a strong oxidant introduced oxygen-containing group and tuned its wettability for better adhesion with the active layer. Polystyrene-grafting on SEBS endowed more aromatic groups for sulfonation to attain highly hydrophilic S-SEBS-g-PSt active layer carrying rich sulfonic acid groups. At a higher sulfonation degree (SD) of 60%, the adhesion strength between the active layer and the support was increased to over 1 MPa, and meanwhile the microphase separation of S-SEBS-g-PSt was enhanced with enlarged and more continuous hydrophilic micro-domain and improved water permeation. An ultra-high water permeance of 109, 000–438, 400 GPU was achieved at 45–85 °C. The outstanding performance of this membrane indicates the promising potential of the SAP composite membrane for practical application.

Studying the Effect of Cross-Linking and Sulfonation on the Calcium-Binding Ability of Polystyrene Sulfonate in the Presence of Dodecyl Sulfate

Calcium ions in hard water deteriorate the cleaning performance of detergents by interacting with the anionic surfactants and inducing their precipitation. Polystyrene sulfonate is a common component of cation-exchange resins that adsorb hard ions such as Ca+2 and Mg+2, which adhere to the sulfonate groups. Therefore, understanding the calcium-binding ability of polystyrene sulfonate in the presence of dodecyl sulfate can help in designing novel water-softening agents for applications related to detergency. Studying the association between polystyrene sulfonate and dodecyl sulfate via calcium ion bridges is also important. Since resins contain cross-linked polystyrene sulfonate, degrees of cross-linking and sulfonation are two important parameters. We use molecular dynamics simulations to study the effect of the above parameters on the calcium-binding ability of isotactic polystyrene sulfonate in the presence of dodecyl sulfate. We observe negligible dependence of calcium-ion binding of polystyrene sulfonate on the degrees of cross-linking and sulfonation. The formation of calcium ion bridges between cross-linked polystyrene sulfonate and dodecyl sulfate is strongly affected by the degree of sulfonation. Such bridges are observed more for the intermediate degrees of sulfonation. This is because, at a very low degree of sulfonation, dodecyl sulfate ions align closer to the cross-linking aromatic groups than the sulfonated ones. On the other hand, at high degrees of sulfonation, stronger electrostatic repulsion disfavors the proximity between dodecyl sulfate and polystyrene sulfonate.

Mesoscale Simulation Based on the Dynamic Mean-Field Density Functional Method on Block-Copolymeric Ionomers for Polymer Electrolyte Membranes.

Block copolymers generally have peculiar morphological characteristics, such as strong phase separation. They have been actively applied to polymer electrolyte membranes for proton exchange membrane fuel cells (PEMFCs) to obtain well-defined hydrophilic regions and water channels as a proton pathway. Although molecular simulation tools are advantageous to investigate the mechanism of water channel formation based on the chemical structure and property relationships, classical molecular dynamics simulation has limitations regarding the model size and time scale, and these issues need to be addressed. In this study, we investigated the morphology of sulfonated block copolymers synthesized for PEM applications using a mesoscale simulation based on the dynamic mean-field density functional method, widely applied to investigate macroscopic systems such as polymer blends, micelles, and multi-block/grafting copolymers. Despite the similar solubility parameters of the monomers in our block-copolymer models, very different morphologies in our 3D mesoscale models were obtained. The model with sulfonated monomers, in which the number of sulfonic acid groups is twice that of the other model, showed better phase separation and water channel formation, despite the short length of its hydrophilic block. In conclusion, this unexpected behavior indicates that the role of water molecules is important in making PEM mesoscale models well-equilibrated in the mesoscale simulation, which results in the strong phase separation between hydrophilic and hydrophobic regions and the ensuing well-defined water channel. PEM synthesis supports the conclusion that using the sulfonated monomers with a high sulfonation degree (32.5 mS/cm) will be more effective than using the long hydrophilic block with a low sulfonation degree (25.2 mS/cm).

Impact of polyelectrolyte adsorption on the rheology of concentrated poly(N-isopropylacrylamide) microgel suspensions.

We explore the impact of three water-soluble polyelectrolytes (PEs) on the flow of concentrated suspensions of poly(N-isopropylacrylamide) (PNIPAm) microgels with thermoresponsive anionic charge density. By progressively adding the PEs to a jammed suspension of swollen microgels, we show that the rheology of the mixtures is remarkably influenced by the sign of the PE charge, PE concentration and hydrophobicity only when the temperature is increased above the microgel volume phase transition temperature Tc, namely when microgels collapse, they are partially hydrophobic and form a volume-spanning colloidal gel. We find that the original gel is strengthened close to the isoelectric point, attained when microgels are mixed with cationic PEs, while PE hydrophobicity rules the gel strengthening at very high PE concentrations. Surprisingly, we find that polyelectrolyte adsorption or partial embedding of PE chains inside the microgel periphery occurs also when anionic polymers of polystyrene sulfonate with a high degree of sulfonation are added. This gives rise to colloidal stabilization and to the melting of the original gel network above Tc. Contrastingly, the presence of polyelectrolytes in suspensions of swollen, jammed microgels results in a weak softening of the original repulsive glass, even when an apparent isoelectric condition is met. Our study puts forward the crucial role of electrostatics in thermosensitive microgels, unveiling an exciting new way to tailor the flow of these soft colloids and highlighting a largely unexplored path to engineer soft colloidal mixtures.

Cross-Linked Sulfonated Poly(arylene ether sulfone) Membrane Using Polymeric Cross-Linkers for Polymer Electrolyte Membrane Fuel Cell Applications.

Cross-linked membranes for polymer electrolyte membrane fuel cell application are prepared using highly sulfonated poly(arylene ether sulfone) (SPAES) and polymeric cross-linkers having different hydrophilicities by facile in-situ casting and heating processes. From the advantage of the cross-linked structures made with the use of polymeric cross-linkers, a stable membrane can be obtained even though the polymer matrix with a very high degree of sulfonation was used. In particular, hydrophilic cross-linker is found to be effective in improving physicochemical properties of the cross-linked membranes and at the same time showing reasonable proton conductivity. Accordingly, membrane electrode assembly made from the cross-linked membrane prepared by using hydrophilic polymeric cross-linker exhibits outstanding cell performance under high temperature and low relative humidity conditions (e.g., maximum power density of 176.4 mW cm-2 at 120 °C and 40% RH).

A novel proton exchange membrane derived from trisulfonated poly(arylene ether phosphine oxide) containing diphenyl ether moieties

A series of novel trisulfonated phosphine oxide polymers (tsPEPO-x) with different sulfonation degrees were prepared by intermolecular polymerization of trisulfonated phosphine monomer and 4,4′-dihydroxydiphenyl ether. The properties of these membranes were investigated in detail. The results showed that these membranes, especially those with high sulfonation degree, exhibited excellent overall performance. For example, the conductivity of tsPEPO-120 membrane reaches 0.093 S cm−1 at 80°C, which is higher than that (0.087 S cm−1) of Nafion 117. At the same time, the swelling rate is almost equivalent to that (20%) of Nafion 117. Moreover, the membrane also has good oxidation resistance in Fenton’s reagent. The obtained polymers showed good properties. The trisulfonated moieties and diphenyl ether simultaneously played important roles in improving the properties of the polymer.

Evaluation of radiation stability of electron beam irradiated Nafion® and sulfonated poly(ether ether ketone) membranes

Proton exchange membranes (PEM), which have been commonly used in fuel cells have raised interest for the application in harsh environments involving ionizing radiation. Therefore, radiation stability and ability to sustain their functionality under the radiation environment are of great interest. Within this study, electron beam irradiation in dose range from 50 to 500kGy was used to evaluate the effects of radiation on the physico-chemical and mechanical properties of two types of PEM: commercial Nafion®117 and sulfonated poly(ether-ether-ketone) (SPEEK) with high degree of sulfonation (DS = 0.75±0.5).SPEEK membrane presented higher mechanical and thermal stability compared to that of Nafion® at doses up to 250 kGy, which was evidenced by infrared and electron paramagnetic resonance spectroscopy, thermal analysis, ion chromatography methods. Tensile tests at room temperature and dynamical mechanical analysis of irradiated membranes revealed improved strength, storage modulus at room and elevated temperatures (80°C) for irradiated SPEEK as compared to pristine PEM. For comparison Nafion® exhibited notable deterioration of mechanical properties including elongation at break due to the predominant oxidation and chain scission already at doses exceeding 50 kGy. The study indicated that SPEEK could be perspective replacement of traditional PEM for application in fuel cells exposed to ionising radiation.

Rigidly and intrinsically microporous polymer reinforced sulfonated polyether ether ketone membrane for vanadium flow battery

Ion exchange membranes (IEMs) blending porous materials have shown great potential for the large-scale energy storage technologies, such as flow battery. However, it remains challenging to overcome the compatibility issue between polymer and porous fillers. In this work, the polymer of intrinsic microporosity (PIM) was successfully introduced into sulfonated polyether ether ketone with high degree of sulfonation (HDS-SPEEK) membrane. PIM exhibited desirable compatibility with HDS-SPEEK due to the natural polymer property. Meanwhile, the rigid skeleton structure of PIM effectively solved the problems of HDS-SPEEK involving poor mechanical property and low vanadium resistance. With increasing the doping of carboxyl grafting modified PIM, the tensile strength increased from 15.22 to 29.94 MPa and the vanadium permeability declined from 4.4 × 10−6 to 1.6 × 10−7 cm2 min−1. As a result, the vanadium flow battery equipped with the optimized blend membrane showed significantly enhanced coulombic efficiency from 55% to 99% at the current density of 20 mA cm−2, and had good long-term stability. This work presents a new route to prepare high-performance IEMs based on porous PIM materials for flow battery.

Ionomers Based on Addition and Ring Opening Metathesis Polymerized 5-phenyl-2-norbornene as a Membrane Material for Ionic Actuators.

Two types of poly(5-phenyl-2-norbornene) were synthesized via ring opening metathesis and addition polymerization. The polymers sulfonation reaction under homogeneous conditions resulted in ionomer with high sulfonation degree up to 79% (IEC 3.36 meq/g). The prepared ionomer was characterized by DSC, GPC, 1H NMR and FT-IR. Polymers for electromechanical applications soluble in common polar organic solvents were obtained by replacing proton of sulfonic group with imidazolium and 1-methylimidazlium. Membranes were prepared using the above-mentioned polymers and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), as well as mixtures with polyvinylidene fluoride (PVDF). Mechanical, morphological, and conductive properties of the membranes were examined by tensile testing, SEM, and impedance spectroscopy, respectively. Dry and air-stable actuators with electrodes based on SWCNT were fabricated via hot-pressing. Actuators with membranes based on methylimidazolium containing ionomers outperformed classical bucky gel actuator and demonstrated high strain (up to 1.14%) and generated stress (up to 1.21 MPa) under low voltage of 2 V.

High performance nanofiltration membrane using self-doping sulfonated polyaniline

Herein, an interlayered-enhanced thin film composite (i-TFC) membrane with excellent separation performance was fabricated using self-doping sulfonated polyaniline (SPANI) nanofibers. SPANI nanofibers were synthesized via two kind of sulfonated reagents and used for comparison. Nanofibrous SPANI can generate an excellent interlayer of membrane, which effectively mediates the IP process and promotes the formation of nanostructured polyamide (PA) layers with superior sieving ability. The increase in degree of sulfonation in an interlayer exhibits superior hydrophilicity, which is favorable for the formation of a thinner and defect-free PA layer. The SPANI of high degree of sulfonation also endows the i-TFC membrane with a high water permeance up to 29.35 ± 1.23 L m−2 h−1 bar−1, while maintaining a competitive selectivity of 4.60 for Mg2+/Na+ and 76.01 for SO42−/Cl−, as well as good retention capacities for both Na2SO4 (98.92 ± 0.45%) and MgSO4 (96.21 ± 0.75%).

Thermally cross-linked sulfonated poly(ether ether ketone) membranes containing a basic polymer-grafted graphene oxide for vanadium redox flow battery application

Sulfonated poly(ether ether ketone) (SPEEK) with a very high degree of sulfonation (DS) and poly(2,5-benzimidazole)-grafted graphene oxide (ABPBI-GO) are prepared and used as a polymer matrix and a filler, respectively, to prepare thermally cross-linked membranes for vanadium redox flow battery (VRFB) application. The thermally cross-linked SPEEK membranes containing ABPBI-GO exhibit significantly enhanced physicochemical stabilities due to the formation of the well-developed cross-linked structures by the chemical bonds formed through the solvothermal process and the acid–base interactions between the benzimidazole groups in filler and sulfonic acid groups in polymer chain. In addition, ABPBI-GO in the polymer matrix is found to be effective in decreasing the vanadium ion permeability while retaining high proton conductivity producing a high-performance VRFB membrane. The ionic selectivity of the thermally cross-linked SPEEK membrane containing 0.5 wt% of ABPBI-GO (TC-SPEEK/0.5) is 13.15 × 107 mS min cm−3, which is approximately 8 times larger than that of Nafion 212 (1.57 × 107 mS min cm−3). Accordingly, the VRFB cell fabricated using TC-SPEEK/0.5 membrane exhibits higher coulombic efficiencies (CE: 98.1–99.4%), voltage efficiencies (VE: 92.5–85.2%), and energy efficiencies (EE: 90.7–84.7%) than that using Nafion 212 (CE: 89.2–93.3%, VE: 90.7–81.2%, EE: 80.9–75.7%) at current density of 40–100 mA cm−2. Furthermore, the long-term stability of the VRFB cell using TC-SPEEK/0.5 membrane evaluated by the cycle test under realistic VRFB operation conditions is also found to be much better than that using Nafion 212.

Synthesis of Polystyrene Sulfonate and Its Characterization as a Polymer Electrolyte Membrane

This study aims to synthesize polystyrene sulfonate (PSS) from polystyrene (PS) isolated from waste styrofoam. Sulfonation reaction of polystyrene was conducted using acetyl sulfonate as sulfonating agents with variation times and temperatures. The sulfonated products were characterized using FT-IR spectrophotometer, degree of sulfonation, cation exchange capacity, water uptake and thermal stability. The FTIR spectrums show vibration of O-H streching at wave number 3300-3400 cm-1, S=O streching at the wave number 1050-1200 cm-1 which indicates the presence of sulfonate groups. Sulfonation reaction at 40oC for 2 hours (SPS-40-2) gives the highest degree of sulfonation, cation exchange capacity, water uptake with values 1,960%, 0.1880 meq/gr, 9.04% respectively. Thermal gravimetry analysis shows that polystyrene sulfonate has better thermal stability than polystyrene.

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.

Ionic Transport and Thermodynamic Interaction in Precision Polymer Blend Electrolytes for Lithium Batteries

AbstractSingle‐ion conducting polymer electrolytes are of interest for use with advanced battery electrodes such as lithium metal, but achieving sufficiently high conductivity has been challenging. In this work, a model system containing charged sites that are precisely spaced along the polymer backbone is explored. Precision sulfonated poly(4‐phenylcyclopentene) lithium salt (p5PhS‐Li) with a high degree of sulfonation (> 90%) is synthesized and blended with poly(ethylene oxide) (PEO) to investigate the thermodynamic and transport properties. Melting point depression is measured via differential scanning calorimetry, ionic conductivity,κ, is determined using electrochemical impedance spectroscopy, and the fraction of current carried by Li+is estimated based on steady‐state current measurements. In conjunction with a density measurement, melting point depression is used to find an effective Flory–Huggins interaction parameter,χeff= − 0.21, suggesting miscibility of the blend.κspans a large range from 2 × 10−11to 2 × 10−7S cm−1over the composition and temperature range investigated. The fraction of charge carried by lithium ions also spans a significant range from 0.12 in majority PEO blend to 0.98 in majorityp5PhS‐Li blend. This study addresses several limitations of sulfonated polystyrene and opens up the possibility of precisely controlling the spacing of other anion types.

Synthesis and Characterization of Polystyrene Sulfonic Acid from Expanded Polystyrene Foam as a Catalyst in the Synthesis of Triacetin

In Indonesia, the composition of waste has gradually changed over time. To reduce expanded polystyrene (EPS) foam waste, we converted it into a heterogeneous acid catalyst, namely Polystyrene Sulfonic Acid (PSSA). The catalyst was then used in an esterification reaction to generate triacetin. In this research, the synthesis of PSSA was performed using a sulfonation reaction with silver sulfate (Ag2SO4) as the catalyst. Based on FTIR analysis, the sulfonation reaction was successful. The use of 0.5% and 1% catalysts led to a significant increase in the degree of sulfonation of PSSA, while there was a relatively constant increase when using 1.5–2.5% catalysts. The highest degree of sulfonation (78.63%) was achieved when the reaction was performed using 2% Ag2SO4 catalyst for 25 min. The PSSA with the highest degree of sulfonation was characterized using X-Ray Diffraction (XRD), SEM-EDX, and BET-BJH. This PSSA had a semi-crystalline structure with a crystallinity of 73.83%, a particle size of 1.75 nm, mesoporous pores with a radius of 16.984 Å, and a sulfur content of 15% (% mass).

Biocompatible Sulphonated PEEK Spheres: Influence of Processing Conditions on Morphology and Swelling Behavior

This work aimed to develop and evaluate the influence of processing variables on the morphology and swelling of sulfonated poly(ether ether ketone) (SPEEK) spheres for possible applications as a biomaterial. We used the drip method to obtain spheres with the polymer starting solutions SPEEK-6 (w/v: 6%) and SPEEK-10 (w/v: 10%), drip rates (20 and 30 mL/h), and drip heights (5 and 10 cm) in experimental planning. The samples were characterized by Fourier-transform infrared spectroscopy (FTIR), optical microscopy (OM), the absorption capacity of phosphate-buffered saline (PBS) by swelling (%), and statistical analysis of data through Design of Experiments (DOE). The obtained results evidenced that the processing variables influenced the morphology and swelling. Spheres with a bigger concentration of the polymer solution presented a greater degree of sulfonation (DS). We verified that the diameter of the spheres was directly related to the variable height and the sphericity was associated with the speed and viscosity of the solution. Bigger and more pores in a greater amount were observed in the spheres with a greater DS, influencing the behavior of the swelling in PBS. The better variable combinations with a high DS, regular sphericity, a smaller diameter, and greater swelling were the samples S2-10-20-5 e S10-10-20-5. The cytotoxicity indicated that the best samples obtained in the experimental planning (S2-10-20-5 and S10-10-20-5) were not toxic. In that regard, the evaluated spheres presented cell viability and swelling capacity, suggesting their possible applications as biomaterials.

A review of alternative polymer electrolyte membrane for fuel cell application based on sulfonated poly(ether ether ketone)

A proton exchange membrane (PEM) is a crucial component in a fuel cell application as a proton carrier and separator for the anode and cathode. Sulfonated poly(ether ketone ether) (SPEEK) has been recognized as one of the promising alternatives PEM in fuel cell application due to the advantagious properties of SPEEK, including the high thermal stability, proton conductivity, mechanical strength, low fuel crossover, and easy to operate. The proton conductivity properties of SPEEK are influenced by the degree of sulfonation (DS). In practical, high DS of SPEEK-based membrane will produce high proton conductivity and a high density of sulfonic acid functional groups grafted into the polymer backbone. However, the excessive production of DS will have side effects on the stability of membrane dimensional and chemical properties. Meanwhile, the low DS of SPEEK has reduced the ability to diffuse the proton within the polymeric matrix. Therefore, getting the optimal DS SPEEK is very important to fabricate the alternative of PEM. But this process is hard. Thus, the researchers have modified the SPEEK membrane with various types of nanoparticles as a filler. This is one of the promising efforts to improve the SPEEK membrane properties and fuel cell application performance. This review aimed to discuss eight conductive materials such as silica, clay, metal oxide, heteropolyacids, carbon, graphene, metal organic framework, and zeolite used as fillers to develop the PEM component based on SPEEK for fuel cell applications. This review also comprehensively discusses the characterization of SPEEK-based membrane modification, including mechanical properties, water intake, proton conductivity, thermal properties, fuel permeability, crystal and structural analysis, chemical oxidation stability, and single-cell performance. Thus, this article can serve as a reference for researchers to planning the best strategies to optimize the properties and performance of the SPEEK-based membrane for fuel cell application.