• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1763-1770
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• 2013

A series of the block copolymers were successfully synthesized from post-sulfonated hydrophilic and hydrophobic macromers via three-step copolymerization. The degrees of sulfonation (DS) of the copolymers (10%, 30%, or 50%) were controlled by changing the molar ratio of the hydrophilic and hydrophobic parts. The resulting block copolymers were characterized by $^1H$ NMR and other technologies. The membranes were successfully cast using dimethyl sulfoxide (DMSO) solution at $100^{\circ}C$. The copolymers were characterized to confirm chemical structure by $^1H$ NMR and FT-IR. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated that all sulfonated block copolymers exhibited good thermal stability with an initial weight loss at temperatures above $240^{\circ}C$. The membranes showed acceptable ion exchange capacity (IEC) and water uptake values in accordance with DS. The maximum proton conductivity was 184 mS $cm^{-1}$ in block copolymer-50 at $60^{\circ}C$ and 100% relative humidity, while the conductivity of Nifion-115 was 160 mS $cm^{-1}$ under the same measurement conditions. AFM images of the block copolymer membranes showed well separated the hydrophilic and hydrophobic domains. From the observed results it is that the prepared block membranes can be considered as suitable polymer electrolyte membranes for the application of polymer electrolyte membrane fuel cells (PEMFC).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.316-317
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• 2009

The ion-exchange membrane, Nafion, remains as the benchmark for a majority of research and development in IPMC technology. In this research, we employed a novel ionomer named by sulfonated poly(styrene-ran-ethylene) (SPSE) that is crosslinked by UV irradiation. The sulfonic acid groups were stable during the UV irradiation crosslinking process. Water uptake, ion exchange capacity, and proton conductivity are characterized for both pure SPSE and crosslinked SPSE membrane. The bending responses of SPSE actuators under both direct current (DC) and alternating current (AC) excitations were investigated. The voltage-current behaviors of the actuators under AC excitations are also measured. Results showed the crosslinked SPSE actuators have better electromechanical performance than that of pure SPSE actuator with regard to tip displacement as a novel smart material.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.98.1-98.1
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• 2011

We present here an isothermal, one-dimensional, steady-state model for a solid alkaline fuel cell (SAFC) with an anion exchange membrane. The conducting ions now move from the cathode to the anode in SAFC. The water is produced at the anode and is also a stoichiometric reactant at the cathode as well as hydrogen and oxygen. In the present model, a net-water-per-proton flux ratio can be predicted and the water transport in the SAFC is explained for various operating conditions.

• Membrane Journal
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• v.18 no.3
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• pp.234-240
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• 2008

This work demonstrates the preparation of proton conducting crosslinked polymer electrolyte membranes by blending polystrene-b-poly(hydroxyethyl acrylate) (PS-b-PHEA) and poly(vinyl alcohol) (PVA) at 1 : 1 wt ratio. The PHEA block of the diblock copolymer was crosslinked with PVA using sulfosuccinic acid (SA) via the esterification reaction between -OH of membrane and -COOH of SA, as confirmed by FT-IR spectroscopy. Ion exchange capacity (IEC) continuously increased from 0.14 to 0.91 meq/g with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. In contrast, the water uptake increased up to 20.0 wt% of SA concentration above which it decreased monotonically. The membrane also exhibited a maximum proton conductivity of 0.024 S/cm at 20.0 wt% of SA concentration. The maximum behavior of water uptake and proton conductivity is considered to be due to competitive effect between the increase of ionic sites and the crosslinking reaction according to the SA concentration.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.149-157
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• 2006

Hydrogen as new energy sources is highly efficient and have very low environmental emissions. The proton exchange membrane fuel cell (PEMFC) is an emerging technology that can meet these demands. Therefore, the preparation of stable polymeric membranes with good proton conductivity and durability are very important for hydrogen production via water electrolysis with PEM at medium temperature above $80^{\circ}C$. Currently Nafion of Dupont and Aciflex of Asahi, etc., solid polymer electrolytes of perfluorosulfonic acid membrane, are the best performing commercially available polymer electrolytes. However, these membrane have several flaws including its high cost, and its limited operational temperature above $80^{\circ}C$. Because of this, significant research efforts have been devoted to the development of newer and cheaper membranes. In order to make up for the weak points and to improve the mechanical characteristics with cross -linking, acid-base complexes were prepared by the combination PSf-co-PPSS-$NH_2$ with PEEK-$SO_3H$. The results showed that the proton conductivity decreased in 17.6% and 40% but tensile strength increased in 78% and 98%, about $20.65\;{\times}\;10^6N/m^2$, in comparison with SBPSf/HPA and SPEEK/HPA complex membrane.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.230-234
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• 2005

Fabrication of MEA is important factor for proton exchange membrane fuel cell (PEMFC). MEA of PEMFC with hot pressing and direct coating method were prepared, and performances were evaluated and compared each other. The effect of MEA preparation methods, hot pressing methods and direct coating methods, on the cell performance was analyzed by impedance spectroscopy and SEM. The performance of PEMFC with direct coating method was better than with hot pressing method because membrane internal resistance and membrane-interfacial resistance were reduced by elimination of hot pressing process in MEA fabrication. In addition the micro structure of MEA with direct coating method reveals uniform interface between membrane and catalyst layer.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.681-686
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• 2010

Two different MFC designs were evaluated in batch mode: single compartment combined membrane-electrodes (SCME) design and twin-compartment brush-type anode electrodes (TBE) design (single chamber with two air cathodes and brush anodes at each side of the reactor). In SCME MFC, carbon anode and cathode electrodes were assembled with a proton exchange membrane (PEM). TBE MFC was consisted of brush-type anode and carbon cloth cathode electrodes without the PEM. A brush-type anode was fabricated with carbon fibers and was placed close to the cathode electrode to reduce the internal resistance. Substrates used in this study were glucose, leachate from cattle manure, or sucrose at different concentrations with phosphate buffer solution (PBS) of 200 mM to increase the conductivity thereby reduce the internal resistance. Hydrogen generating bacteria (HGB) were only inoculated in TBE MFC. The peak power densities ($P_{peak}$) produced from the SCME systems fed with glucose and leachate were 18.8 and $28.7mW/m^2$ at external loads of 1000 ohms, respectively. And the $P_{peak}$ produced from TBE MFC were 40.1 and $18.3mW/m^2$ at sucrose concentration of 5 g/L and external loads of 470 ohms, with a mediator (2-hydroxy-1, 4-naphthoquinone) and without the mediator, respectively. The maximum power density ($P_{max}$) produced from mediator present TBE MFC was $115.3mW/m^2$ at 47 ohms of an external resistor.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.391-398
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• 2007

The covalently cross-linked sulfonated polyetheretherketone (CL-SPEEK) membrane was prepared by four-step synthesis of sulfonation-sulfochlorination, partial reduction, lithiation, and cross-linking, and its electrochemical and mechanical properties were investigated for water electrolysis application. The prepared ion exchange membranes showed good electrochemical and mechanical properties; proton conductivity of 0.116 S/cm at $80^{\circ}C$, water uptake of 44.6%, ion exchange capacity of 1.75 meq/g-dry-memb., tensile strength of 64.25 MPa and elongation of 61.11%. The membrane electrode assembly (MEA) with homemade membranes were prepared by non-equilibrium impregnation-reduction (I-R) method. Especially, the electrochemical surface area (ESA) and roughness factor of CL-SPEEK electrolyte by cyclic voltammetry method were 23.46 $m^2/g$ and 307.3 $cm^2-Pt/cm^2$, respectively. The prepared MEA was used in the unit cell of water electrolysis and the cell voltage was 1.81 V at 1 A/$cm^2$ and $80^{\circ}C$, with platinum loadings of 1.31 mg/$cm^2$.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.302-306
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• 2017

Humidity affect performance and durability of proton exchange membrane fuel cell (PEMFC). High humidity of gases generally enhance the performance, but high humidity have the danger of flooding. I-V performance, linear sweep voltammetry, cyclo voltammetry, and impedance of micro-channel cell measured with change of relative humidity (RH). Flooding phenomena started at RH 70%. Ion conductivity of membrane reached maximum value at RH 80%. Maximum current density of $1,700mA/cm^2$ (at 0.6 V) was obtained at RH 80%. Therefore the effect of ion conductivity increasement was higher than that of mass transfer decrease by flooding at RH 80%.