• Membrane Journal
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• v.32 no.5
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• pp.275-282
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• 2022

In contemporary days, hydrogen-based energies including batteries are renowned to be effective. And its effectiveness comes from the fact that it possesses high efficiency as an energy carrier. Eco-friendly and high purity of hydrogens comes out from water electrolysis. And among different types of electrolysis, proton exchange membrane (PEM) water electrolysis is considered the most renewable, cheap, and eco-friendly. It produces oxygen and hydrogens which are feasible in using as energies. Since it has such a number of benefits, increased research is going on in PEM electrolysis. Nafion is widely used as PEM, but high cost and various other disadvantages leads to the exploration of alternative materials. This review is broadly classified into Nafion and non Nafion based PEM for water electrolysis.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.144-149
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• 2005

Sulfonated poly(ether ether ketone) (SPEEK) was blended with poly(ether sulfone) (PES) at various compositions. To investigate the possibility of using the blend membranes as polymer electrolyte membranes for direct methanol fuel cell, the blend membranes were characterized in terms of methanol permeability, proton conductivity, ion exchange capacity, and water content. Both proton conductivity and methanol permeability of SPEEK were relatively high. As the amount of PES increased, methanol permeability decreased more rapidly compared to proton conductivity. The experimental results indicated that the blend membrane with 40 wt% PES was the best choice in terms of the ratio of proton conductivity to methanol permeability.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.332-339
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• 2021

Recently, due to concerns about the depletion of fossil fuels and the emission of greenhouse gases, the importance of hydrogen energy technology, which is a clean energy source that does not emit greenhouse gases, is being emphasized. Water electrolysis technology is a green hydrogen technology that obtains hydrogen by electrolyzing water and is attracting attention as one of the ultimate clean future energy resources. In this study, the surface properties of the porous transport layer (PTL), one of the cell components of the proton exchange membrane water electrolysis (PEMWE), were controlled using a sandpaper to reduce overvoltage and increase performance and stability. The surfaces of PTL were sanded using sandpapers of 400, 180, and 100 grit, and then all samples were finally treated with the sandpaper of 1000 grit. The prepared PTL was analyzed for the degree of hydrophilicity by measuring the water contact angle, and the surface shape was observed through SEM analysis. In order to analyze the electrochemical characteristics, I-V performance curves and impedance measurements were conducted.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.413-422
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• 2015

Proton exchange membrane (PEM), which transfers proton from the anode to the cathode, is the key component of the proton exchange membrane fuel cell (PEMFC). Nafion is widely used as PEM due to its high proton conductivity as well as excellent chemical and physical stabilities. However, its high cost and the environmental hazards limit the commercial application in PEMFCs. To overcome these disadvantages, various alternative polymer electrolytes have been investigated for fuel cell applications. We used densely sulfonated polymers to maximize the ion conductivity of the corresponding membrane. To overcome high swelling, dipole-dipole interaction was used by introducing nitrile groups into the polymer backbone. As a result, physically-crosslinked membranes showed improved swelling ratio despite of high water uptake. All the membranes with different hydrophilic-hydrophobic compositions showed higher conductivity, despite their lower IEC, than that of Nafion-117.

• Membrane Journal
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• v.29 no.5
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• pp.252-262
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• 2019

A sulfonated star branched poly(styrene-b-butadiene-b-styrene) triblock copolymer (SSBS) was synthesized with varying degrees of sulfonation. The effective sulfonation on the butadiene block was confirmed by FT-IR spectroscopy. Ion exchange capacity by titration was used to determine the degree of sulfonation. The synthesized polymer observed enhanced water uptake and proton conductivity. At room temperature, the SSBS with 25 mol% degree of sulfonation showed an outstanding proton conductivity of 0.114 S/cm, similar to that of commercial membrane, Nafion. The effect of temperature at constant relative humidity on conductivity resulted to a remarkable increase in proton conductivity. Methanol permeability studies showed a value lower than Nafion for all the sulfonated membranes. Structural nature observed using AFM showed that the membranes observed microphase separated nanostructures and the connectivity of the interionic channels.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1173-1182
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• 2018

Mesoporous silica allows proper hydration of an ion exchange membrane under low relative humidity due to its strong hydrophilicity and structural characteristic. A mesoporous silica and Nafion composite membrane shows good proton conductivity under low relative humidity. An understanding of ion-channel formation and proton transfer through an ion-channel network in mesoporous silica and Nafion composite membranes is essential for the development and the optimization of ion exchange membranes. In this study, a mesoporous cellular foam $SiO_2/Nafion$ composite membrane is fabricated, and its proton conductivity and performance are measured. Also, the ion-channel distribution is analyzed by using electrostatic force microscopy to measure the surface charge density of the mesoporous cellular foam $SiO_2/Nafion$ composite membrane. The research reveals a few remarkable results. First, the composite membrane shows excellent proton conductivity and performance under low relative humidity. Second, the composite membrane is observed to form ion-channel-rich and ion-channel-poor region locally.

• The Korean Journal of Physiology
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• v.25 no.1
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• pp.49-60
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• 1991

The change of the acridine orange absorbance was used to monitor the formation and/or dissipation of a pH gradient in microvillous membrane vesicles (MVV) isolated from human term placenta. Under $Na^+$ efflux conditions, an acidification of the intravesicular space occured and it was completely inhibited by 0.1 mM amiloride. Under $K^+$ efflux conditions, an acidification of the intravesicular space occured and it was potentiated by valinomycin or FCCP. An inwardly directed chloride gradient also induced a minor intravesicular acidification, but it was not observed in voltage-clampled MVV. The initial rate of the dissipation of a pH gradient was accelerated by pulse injections of $Na^+$ in a saturable manner and $Li^+$ could replace $Na^+$. The kinetic parameter of $Na^+$ in placental $Na^+/H^+$ exchange was similar to that of renal $Na^+/H^+$ exchange. Amiloride was a inhibitor of directly coupled $Na^+/H^+$ exchange and its $IC_{50}$ in placental MVV was about 14-fold higher than that in renal brush border membrane. These results indicate that $Na^+/H^+$ exchanger exists in human placental MVV and that its kinetic characteristics is similar to that of renal $Na^+/H^+$ exchanger but its pharmacological characteristics is different. In placental MVV $K^+,\;H^+$, and, relatively minor chloride conductances are present. The magnitude of $Cl^-/OH^-$ exchange, even though it exists, seems to be smaller than that of $Na^+/H^+$ exchange.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.269-269
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• 2006

The molecular structure of poly(2,6-dimethyl-4,4' -phenylene oxide)-g-poly (styrenesulfonic acid) (PPO-g-PSSA) graft copolymer was designed, and synthesized via living radical polymerization. Obtained graft copolymers were transformed into proton exchange membranes for direct methanol fuel cell (DMFC) application. The performance of the membranes was measured in terms of water uptake, proton conductivity, methanol permeability, and thermal stability. Very low methanol permeability and good proton conductivity were observed by adjusting grafting frequency and PSSA block content.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.167-172
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• 2009

Direct methanol fuel cells(DMFCs) are receiving significant attention in the portable power source and electric vehicular transportation because of its high energy efficiency as liquid fuel, low cost, and no requirement of fuel reforming process. In this study, we synthesized the Sulfonated poly(ether ether ketone) (SPEEK) to evaluate the possibility of use as a proton exchange membrane for DMFC. And poly(vinylidienedifluoride) (PVDF) was used to increase proton conductivity in SPEEK and simultaneously to prevent methanol transport through the cross linked membrane. Furthermore, in order to improve the electrical composite properties for DMFC applications.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.61-64
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• 2004

The proton transport through proton exchange membranes is controlled by the distribution of hydrated structure connected with negative-charged fixed ions such as phosphonic acid, carboxylic acid and sulfonic acid, or water molecules within the membrane.(omitted)