Elucidating the solvent-modulated self-assembly nanostructures of high ion exchange capacity short-side-chain perfluorosulfonic acid dispersions

Lightly cross-linked poly(4-vinyl pyridine) has been synthesized from 4-vinyl pyridine and a small amount of ethylene glycol dimethacrylate (EGDMA) in aqueous medium through micelle technique. The polymer is then quaternized with 1,4-dibromobutane to develop an anion exchange resin with high selectivity and ion exchange capacity at a wide range of pH and temperature. The material exhibits high ion exchange capacity and reverse anion selectivity order compared to commercially available anion exchanger. A method has been designed to separate chromate and sulfate using the synthesized material.

New generation radiation-grafted PVDF-g-VBC based dual-fiber electrospun anion exchange membranes

The unique functions of nanofibers (NFs) are based on their nanoscale cross-section, high specific surface area, and high molecular orientation, and/or their confined polymer chains inside the fibers. The introduction of ion-exchange (IEX) groups on the surface and/or inside the NFs provides de novo ion-exchangers. In particular, the combination of large surface areas and ionizable groups in the IEX-NFs improves their performance through indices such as extremely rapid ion-exchange kinetics and high ion-exchange capacities. In reality, the membranes based on ion-exchange NFs exhibit superior properties such as high catalytic efficiency, high ion-exchange and adsorption capacities, and high ionic conductivities. The present review highlights the fundamental aspects of IEX-NFs (i.e., their unique size-dependent properties), scalable production methods, and the recent advancements in their applications in catalysis, separation/adsorption processes, and fuel cells, as well as the future perspectives and endeavors of NF-based IEMs.

Ionothermal synthesis of aluminophosphates used for ion exchange: Influence of choline chloride/urea ratio

Solid polymer electrolyte electrochemical energy conversion devices that operate under highly alkaline conditions afford faster reaction kinetics and the deployment of inexpensive electrocatalysts compared with their acidic counterparts. The hydroxide anion exchange polymer is a key component of any solid polymer electrolyte device that operates under alkaline conditions. However, durable hydroxide-conducting polymer electrolytes in highly caustic media have proved elusive, because polymers bearing cations are inherently unstable under highly caustic conditions. Here we report a systematic investigation of novel arylimidazolium and bis-arylimidazolium compounds that lead to the rationale design of robust, sterically protected poly(arylimidazolium) hydroxide anion exchange polymers that possess a combination of high ion-exchange capacity and exceptional stability.

This work describes the preparation of the cellulose phosphate with high ion exchange capacity from rice straw and bagasse for removal of heavy metals. In this study, rice straw and bagasse were modified by the reaction with phosphoric acid in the presence of urea. The introduced phosphoric group is an ion exchangeable site for heavy metal ions. The reaction by microwave heating yielded modified rice straw and modified bagasse with greater ion exchange capacities (∼3.62 meq/g) and shorter reaction time (1.5–5.0 min) than the phosphorylation by oil bath heating. Adsorption experiments towards Pb2+, Cd2+, and Cr3+ ions of the modified rice straw and the modified bagasse were performed at room temperature (heavy metal concentration 40 ppm, adsorbent 2.0 g/L). The kinetics of adsorption agreed with the pseudo-second-order model. It was shown that the modified rice straw and the modified bagasse could adsorb heavy metal ions faster than the commercial ion exchange resin (Dowax). As a result of Pb2+ sorption test, the modified rice straw (RH-NaOH 450W) removed Pb2+ much faster in the initial step and reached 92% removal after 20 min, while Dowax (commercial ion exchange resin) took 90 min for the same removal efficiency.

Aluminum ion-activated low-temp pyrolyzed carbon to decontaminate Cr in water and soil.

Reduced graphene oxide/polyaniline conductive anion exchange membranes in capacitive deionisation process

High-performance ion exchange membranes with high ion exchange capacity (IEC), excellent mechanical properties, lower membrane resistance and superior ions conductivity were developed with chemical-induced polymerization in this work. Through a series of synthesizing experiments, structure characterization and properties testing for polyolefin-based cation exchange membrane (CEM) and anion exchange membrane (AEM), LDPE proved to be an optimized backbone material. The CEM with 57.5% styrene, 38.4% LDPE, 3% crosslinking degree and 1% initiator addition yield the highest IEC value (1.72 mol/g) and moderate burst strength. The 10% addition of styrene was found to enhance IEC of 57% to AEM. However, continually increase styrene leaded lower IEC due to the decreasing grafting degree of vinyl benzene chloride (VBC) on polyethylene.

Abnormal phenomena caused by climate change require the realization of carbon neutrality while ensuring a stable supply of energy (energy security). Climate change is mainly caused by environmental pollution from human society, and in recent years, research and development of environmentally friendly materials for practical use has been carried out.Energy devices such as fuel cells, water electrolysis, and RFB have polymer electrolyte components that transport ions, and up until now, fluorine-based electrolytes such as Nafion have been mainly used. However, within the framework aiming to achieve carbon neutrality, the development of materials containing fluorine is thought to be subject to restrictions. Therefore, there is a need for alternative materials to fluorine-based electrolytes.We are conducting research aimed at the practical application of sulfonated PPSU, a hydrocarbon electrolyte, as a non-fluorine electrolyte [1-6]. In this study, we report the synthesis and properties of sulfonated PPSU with high ion exchange capacity (IEC) (calculated value: 5.55meq/g), which has four sulfo groups per repeating unit of PPSU.SPPSU (2S), which has two sulfo groups per repeating unit of PPSU (IEC=3.57meq/g), was obtained by sulfonation of bis(4-fluorophenyl)sulfone using 30% Oleum. Next, polymerization was performed by condensation reaction of sulfonated bis(4-fluorophenyl)sulfone (SFPS) and 4,4'-biphenol (BP). Furthermore, by sulfonating these polymers in sulfuric acid, SPPSU (4S) having four sulfo groups per repeating unit (IEC=5.55meq/g) was synthesized. The molecular weight of SPPSU(4S) was 130,304 – 303,203. Depending on the sulfonation conditions using SPPSU(2S) polymer and sulfuric acid, the viscosity of SPPSU(4S) was 30 to 270 mP·s, which was higher than that of Nafion (D520CS), which was 10 to 40 mPa·s. In addition, the tensile strength, tensile elongation, and flexural modulus of SPPSU (4S) were 22 MPa, 251%, and 296 MPa. Compared to Nafion 212, it exhibited high tensile strength and flexural modulus while having similar tensile elongation properties. Furthermore, the conductivity of SPPSU (4S) was 11.3 mS/cm at 120°C and RH 10%. This value was approximately 4 times higher than the conductivity of Nafion212 (3.2 mS/cm) under the same conditions.References J.D. Kim, A. Donnadio, M. S. Jun, M.L. Di Vona, “Crosslinked SPES-SPPSU membranes for high temperature PEMFCs”, Int. J. Hyd. Ener., 2013, 38, 1517-1523.J.D. Kim, L.-J. Ghil, “Annealing effect of highly sulfonated polyphenylsulfone polymer”, Int. J. Hyd. Ener., 2016, 41, 11794-11800.Y. Zhang, J.D. Kim, K. Miyatake, “Effect of thermal crosslinking on the properties of sulfonated poly(phenylene sulfone)s as proton conductive membranes”, J. Appl. Poly. Sci., 2016, 133(46) 44218-44225.J.D. Kim, A. Ohira, H. Nakao, “Chemically crosslinked sulfonated polyphenylsulfone (CSPPSU) membranes for PEM fuel cells”, membranes, 2020, 10, 31-44.J.D. Kim, A. Ohira, “Crosslinked sulfonated polyphenylsulfone (CSPPSU) membranes for elevated-temperature PEM water electrolysis”, membranes, 2021, 11, 861-873.J.D. Kim, Y. Zhang; Japan patent no. 6548176, EU patent no. EP3340350, US patent no. US1086215.

Polymer electrolyte membrane fuel cells (PEFCs) have attracted considerable attention due to their high efficiency and clean electric generating system. Especially, in terms of the catalytic activity and water management, there is a great demand for operation under high temperature and low relative humidity. Under such situation, we recently succeeded in the development of heat–resistant electrolyte membrane (PI-CLSPES) with high ion exchange capacity (IEC) from porous polyimide (PI) substrates and highly sulfonated polyethersulfones (SPES150: IEC = 4.9meq/g) by using both polymer-filling and thermal cross–linking methods. The PI substrate can be prepared by using the viscolastic phase separation phenomenon: multi-stage solvent replacement of polyammic acid (PAA) cast film into N-methyl-2-pyrrolidone (NMP) and methanol, followed by thermal treatment. We found that the changes in viscosity of PAA solution, thickness of PAA cast film and immersion time afford the PI substrates with various pore sizes. On the other hand, the SPES150 membrane with high IEC is obtained by further sulphonation of sulfonated poly(arylene ether sulfone) (SPES50) in concentrated sulfuric acid, and allowed for impregnation into the pores of the porous PI substrate. The SPES150 inside the PI pores can be cross-linked between the sulfonic acid and phenyl groups by appropriate thermal treatment, and consequently, lead to the high thermal stability and suppression of membrane swelling. Moreover, the pore-filling and cross-linked membranes still retain the high IEC, and displayed the superior proton conductivity under high temperature comparable to that of Nafion. The detailed proton conducting behavior of the polymer electrolyte membranes as well as their structural analysis will be presented.

Facile fabrication of carbon nanotube embedded pore filling ion exchange membrane with high ion exchange capacity and permselectivity for high-performance reverse electrodialysis

Ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties as proton conductive membranes

Widespread of fuel cells are strongly desired from the point of reducing the GHG and for clean environment. In order to achieve these, reducing the cost of the fuel cell vehicle is needed and from this point, higher operating temperatures of PEFC can contribute for designing compact and simple cooling system. We have been developing variety of new Perfluorosulfonic acid (PFSA) ionomers having high ion exchange capacity (IEC) and other properties required for each the membrane and the electrolyte in the electrodes. The ionomer with high proton conductivity was tested by copolymerization of tetrafluoroethylene with a new bifunctional fluorosulfonyl monomer 1. The ion exchange capacity was 1.58 meq/g and the water uptake after immersion in hot water at 80 °C for 16 hours was much lower compared to that of conventional ionomer. Reduction in Pt loading in the cathode is another requirement for PEFC to reduce the cost. Especially at higher temperature and lower RH conditions under which the flux of oxygen to the Pt surface through the ionomer in the electrode could be the rate limiting factor for the oxygen reduction reaction (ORR). In order to increase the oxygen flux to Pt surface, the use of ionomers having higher oxygen permeability can be a solution. We have designed and synthesized various ionomers based on a general rule that the lower the density of a fluorinated polymer, the higher the oxygen permeability. One of the newly prepared ionomer having lower density showed more than 2 times higher the oxygen permeability 2 at low RH conditions. The use of this high oxygen permeable ionomer at cathode showed the possibility of achieving the same cell voltage with half the amount of Pt loading.We see that the ionomer plays an important row in developing PEFC achieving the requirements from the market. The ionomer can also be used in the micro porous layers (MPLs) between the catalyst layers and the Gas diffusion substrate to create hydrophilic MPLs. Conventionally, hydrophobic MPLs were applied between the GDM and the catalyst layer to prevent flooding due to excess water in the electrode. But the hydrophobicity of the MPL is not favorable when the cell is operating under a dry condition. We have been reporting the use of hydrophilic MPL between the GDM and the catalyst layer 3. It can control the water balance in the MEA, achieving higher performance under low RH conditions without facing the low performance due to mass transfer issue at wet conditions. This hydrophilic MPL was used in the cathode in combination with a high proton conductive membrane, and the MEA showed excellent performance under a very dry condition. We are continuously making efforts developing PEFC materials getting into the next stage.

Ionomer network of catalyst layers for proton exchange membrane fuel cell