• Membrane Journal
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• v.30 no.6
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• pp.433-442
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• 2020

In this study, in order to build a molecular dynamics simulation model of ionomer for water electrolysis, an ionomer model that reflects the characteristics of a water electrolysis system in which excess water molecules exist was compared to an ionomer built according to the conventional simulation method of the fuel cells membrane. The final ionomer MD models have a strong phase separation and water channel that is one of the important characteristics of the perfluorinated ionomer, and are stable and water-insoluble under excessive water and high temperature conditions. In the ionomer MD models built in this study, the excess water molecules decrease an ion conductivity due to the dilution of ions, but increase a hydrogen diffusivity. Therefore, it is necessary to design the molecular structure of ionomers for water electrolysis in experimental studies as well as molecular dynamics studies according to the characteristics of the water electrolysis system reported in this study.

• Membrane Journal
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• v.14 no.3
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• pp.250-257
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• 2004

PEG(poly(ethylene glycol)) acrylate/PPG(poly(propylene glycol)) acrylate (PEG/PPG) was prepared using UV induced photopolymerization method to investigate gas permeation properties of the membrane. The effect of PPG content on the solubility, diffusivity, and permeability of $CO_2$, $O_2$, and $N_2$ in PEG/PPG membrane is reported at $25^{\circ}C$ and $35^{\circ}C$. PEG/PPG (9:1) membrane exhibits $CO_2$ permeability coefficient of 28.9 barrer and $CO_2$/$N_2$ pure gas selectivity of 57.9 at $25^{\circ}C$. Permeability coefficient of increased with increasing with PPG content in the membrane. PEG/PPG (5:5) membrane shows $CO_2$ permeability coefficient of 78.9 barrer and $CO_2$/$N_2$ pure gas selectivity of 33.2 at $25^{\circ}C$.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3140-3141
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• 2008

The output power efficiency of the fuel cell system depends on the demanded current, stack temperature, air excess ratio, hydrogen excess ratio and inlet air humidity. Thus, it is necessary to determine the optimal operation condition for maximum power efficiency. In this paper, we developed a dynamic model of fuel cell system which contains mass flow model, diffusivity gas layer model, membrane hydration and electrochemistry model. In order to determine the maximum output power and minimum use of hydrogen in a certain power condition, response surface methodology (RSM) optimization based on the proposed PEMFC stack model is presented. The results provide an effective method to optimize the operation condition under varied situations.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.3
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• pp.119-125
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• 1998

The modified statistical-mechanical theory for dense fluid mixtures of rigid spheres has been applied to rigid sphere fluids in the nonoverlapping pore model. The resulting expressions for the partition coefficient and diffusivity illustrate the influence of steric hindrance on the thermodynamic and transport properties in such systems. The open membrane model without the size-exclusion and shielding effects shows considerable overestimation of the diffusion flux when the effective mean pore radii of the order of $20{\AA}$ or less are involved. Theoretical predictions investigated here were also compared with experimental data for hydrogen gases in inorganic porous membranes and it was observed a qualitative agreement in the low pressure limit.

• Membrane Journal
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• v.27 no.6
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• pp.499-505
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• 2017

The increasing number of natural disasters resulting from anthropogenic greenhouse gas emissions has prompted the development of a gas separation membrane. Carbon dioxide ($CO_2$) is the main cause of global warming. Organic polymeric membranes with inherent flexibility are good candidates for use in gas separation membranes and poly(dimethyl siloxane)(PDMS) specifically is a promising material due to its inherently high $CO_2$ diffusivity. In addition, poly(vinyl pyrrolidine)(PVP) is a polymer with high $CO_2$ solubility that could be incorporated into a gas separation membrane. In this study, poly(dimethyl siloxane)-poly(vinyl pyrrolidine)(PDMS-PVP) comb copolymers with different compositions were synthesized under mild conditions via a simple one step free radical polymerization. The copolymerization of PDMS and PVP was characterized by FTIR. The morphology and thermal behavior of the produced polymers were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Composite membranes composed of PDMS-PVP on a microporous polysulfone substrate layer were prepared and their $CO_2$ separation properties were subsequently studied. The $CO_2$ permeance and $CO_2/N_2$ selectivity through the PDMS-PVP composite membrane reached 140.6 GPU and 12.0, respectively.

• Membrane Journal
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• v.25 no.5
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• pp.398-405
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• 2015

Facilitated transport is considered to be a possible solution to simultaneously improve permeability and selectivity, which is challenging in normal polymeric membranes based on solution-diffusion transport only. We investigated the effect of adding mesoporous $TiO_2$ ($m-TiO_2$) upon the separation performance of facilitated olefin transport membranes comprising poly(vinyl pyrrolidone), Ag nanoparticles, and 7,7,8,8-tetracyanoquinodimethane as the polymer matrix, olefin carrier, and electron acceptor, respectively. In particular, $m-TiO_2$ was prepared by means of a facile, mass-producible method using poly(vinyl chloride)-g-poly(oxyethylene methacrylate) graft copolymer as the template. The crystal phase of $m-TiO_2$ consisted of an anatase/rutile mixture, of crystallite size approximately 16 nm as determined by X-ray diffraction. The introduction of $m-TiO_2$ increased the membrane diffusivity, thereby increasing the mixed-gas permeance from 1.6 to 16.0 GPU ($1GPU=10^{-6}cm^3$(STP)/($s{\times}cm^2{\times}cmHg$), and slightly decreased the propylene/propane selectivity from 45 to 37. However, both the mixed-gas permeance and selectivity of the membrane containing $m-TiO_2$ rapidly decreased over time, whereas the membrane without $m-TiO_2$ had more stable long-term performance. This difference might be attributed to specific chemical interactions between $TiO_2$ and Ag nanoparticles, causing Ag to lose activity as an olefin carrier.

• Clean Technology
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• v.9 no.4
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• pp.169-177
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• 2003

In order to develope a clean technology by liquid-supported membrane of ionic liquid/PVDF, the solubility of R22 and HFP gases using BMIBF4 as ionic liquid were measured at temperatures from 0 to $30^{\circ}C$, at total pressures up to 4 bars. The solubility of R22 in this ionic liquid was shown a rapid increasing tendency with increases of pressure and decreases of temperature, respectively, whereas the solubility of HFP was showed only a little in the same conditions. Based on these results, liquid-supported membranes of ionic liquid/PVDF were prepared by variables of the deposition amount of ionic liquid in polymer matrix, PVDF and were applied to the separation of fluoro-gases(R22, HFP) including $N_2$ gas. The permeability of R22 was rapidly increased by depending on the deposition amounts of ionic liquid, whereas both of HFP and $N_2$ were just showed so little. Especially, the diffusivity coefficient and solubility parameter of R22 were increased by lower operating temperatures and increased deposition amount of ionic liquid in 1iquid membrane. In conclusion, the selectivity of R22 against HFP was changed to 10-45 times depending on both of operating temperatures and the deposition amount of ionic liquid in BMIBF4/PVDF liquid membrane.

• Membrane Journal
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• v.21 no.3
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• pp.213-221
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• 2011

Using poly(ethylene oxide) (PEO) as a polymer host, poly(ethylene glycol) (PEG) as a plasticizer, potassium iodide and iodine as sources of $I^-/I_3^-$, polymer electrolyte membranes were prepared. Based on the polymer electrolytes, solid-state dye-sensitized solar cell (DSSC)s were fabricated. The content of PEG in the electrolyte was controlled to be 95%. The mole number of KI per 1 mole of EO ([KI]/[EO] ratio) in the electrolyte was changed to be 0.022, 0.044, 0.066 and 0.088. The electrolyte membrane showed wax phase in ambient temperature. The ionic conductivity increased with increasing KI content to reach the maximum value at which [KI]/[EO] ratio is 0.066. After the maximum value, the ionic conductivity decreased with increasing KI content. In the case of DSSC, the Voc decreased continuously with increasing KI content in the polymeric electrolyte membrane. The $J_{SC}$ increased with increasing KI content to show maximum value at which [KI]/[EO] ratio is 0.044. In the higher KI content region, $J_{SC}$ value decreased with increasing KI content.

• Membrane Journal
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• v.20 no.1
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• pp.13-20
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• 2010

Using poly(ethylene oxide) (PEO) as a polymer host, poly(ethylene glycol) (PEG) as a plasticizer, potassium iodide and iodine as sources of $I^-/{I_3}^-$ PEO-PEG-KI/$I_2$ polymer gel electrolytes were prepared. Based on the polymer gel electrolytes, solid-state dye-sensitized solar cell(DSSC)s were fabricated. The content of PEG in the electrolyte was changed from 0 to 85%. The electrolyte showed self-supporting form through whole range of the PEG content. As the PEG content increased, the ionic conductivity and ${I_3}^-$ diffusivity increased and the light-to electrical energy conversion efficiency increased under irradiation of 100 $mWcm^{-2}$ simulated sunlight.

• Membrane Journal
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• v.19 no.3
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• pp.237-243
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• 2009

Polyimides synthesized by using 2,2'-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and 4,4'-diaminodiphenylmethane (DAM) were sulfonated according to reaction times, 5 min to 20 min. And the resulting polyimide membranes were investigated in terms of permeability and separation factor for $N_2$, $O_2$, and $CO_2$ gases. The introduction of bulky group, $-{SO_3}H$, leads to the decreases of both diffusivities and solubilities for all the range of reaction times. At 20 min of sulfonation, the diffusivity and solubility of $N_2$ decrease up to 21% and 26%, respectively. Overall separation efficiencies for $O_2/N_2$ and $CO_2/N_2$ increase as the reaction time increases to 20 min.