• Transactions of the Korean hydrogen and new energy society
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• v.29 no.5
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• pp.458-465
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• 2018

This study reports the fabrication of anion exchange membranes (AEMs) containing two kinds of functional groups: i) trimethylphosphite (TMP) and ii) trimethylamine (TMA). We carried out the synthesis of polymers to enhance thermal stability and ion conductivity. The alternative polymer was prepared using 2,2-bis(4-hydroxy-3-methylphenyl)propane and decafluorobiphenyl. The membrane was fabricated by solution casting method. The thermal stability of membranes was examined by TGA. The physiochemical properties of membranes were also investigated in terms of water uptake, swelling ratio, ion exchange capacity, and ion conductivity. The hydroxide ion conductivity of the membranes reached about 20.2 mS/cm for quaternary ammonium poly(arylene ether) (QA-PAE) containing TMA moiety and 5.1 mS/cm for quaternary phosphonium PAE (QP-PAE) containing TMP moiety at $90^{\circ}C$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.5
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• pp.299-308
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• 2022

This study was conducted to predict the tendency for heat exchange and boil-off gas (BOG) in a liquefied hydrogen tank under sloshing excitation. First, athe fluid domain excited by sloshing was modeled using a multiphase-thermal flow domain in which liquid hydrogen and hydrogen gas are in the saturated state. Both the the volume of fluid (VOF) and Eulerian-based multi-phase flow methods were applied to validate the accuracy of the pressure prediction. Second, it was indirectly shown that the fluid velocity prediction could be accurate by comparing the free surface and impact pressure from the computational fluid dynamics with those from the experimental results. Thereafter, the heat ingress from the external convective heat flux was reflected on the outer surfaces of the hydrogen tank. Eulerian-based multiphase-heat flow analysis was performed for a two-dimensional Type-C cylindrical hydrogen tank under rotational sloshing motion, and an inflation technique was applied to transform the fluid domain into a computational grid model. The heat exchange and heat flux in the hydrogen liquid-gas mixture were calculated throughout the analysis,, whereas the mass transfer and vaporization models were excluded to account for the pure heat exchange between the liquid and gas in the saturated state. In addition, forced convective heat transfer by sloshing on the inner wall of the tank was not reflected so that the heat exchange in the multiphase flow of liquid and gas could only be considered. Finally, the effect of sloshing on the amount of heat exchange between liquid and gas hydrogen was discussed. Considering the heat ingress into liquid hydrogen according to the presence/absence of a sloshing excitation, the amount of heat flux and BOG were discussed for each filling ratio.

• Journal of the Korean institute of surface engineering
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• v.55 no.3
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• pp.180-186
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• 2022

The production of hydrogen via water electrolysis (i.e., green hydrogen) using renewable energy is key to the development of a sustainable society. However, most current electrocatalysts are based on expensive precious metals and require the use of highly purified water in the electrolyte. We demonstrated the preparation of a non-precious metal catalyst based on CuCo₂O₄ (CCO) via simple electrodeposition. Further, an optimization process for electrodeposition potential, solution concentration and electrodeposition method was develop for a catalyst-substrate integrated electrode, which indicated the highly electrocatalytic performance of the material in electrochemical tests and when applied to an anion exchange membrane water electrolyzer.

• New & Renewable Energy
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• v.18 no.2
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• pp.50-59
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• 2022

The Korean government announced the "1st Basic Plan for the Transition to Hydrogen Economy" in 2021 and declared the establishment of a hydrogen industry ecosystem by 2040. To build a low-carbon power system, resources that can efficiently accommodate renewable energy are required, and green hydrogen is considered a potential solution. This study analyzed the economic feasibility of green hydrogen-based sector coupling to reduce curtailment of renewable generation in the Jeju power system by 2025 under the scenario of with or without HVDC#3. The result showed that HVDC#3 significantly reduced the frequency of curtailment from 16.1% to 3.0%. In addition, green hydrogen-based sector coupling was an economically feasible option as result showed an IRR of 4.86% when HVDC#3 was connected and 11.45% when it was not under the condition of achieving 50% curtailment reduction. This study shows that the higher the level of renewable energy deployment, the more delayed the HVDC connection between Jeju and the main land, and the lower the SMP, the more economically feasible the green hydrogen-based sector coupling is. Furthermore, this study suggests that the policy goal of completely reducing curtailment is not economically efficient.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.319-327
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• 2022

Ion exchange membranes have been developed from laboratory tools to industrial products with significant technical and trade impacts in the last 70 years. Today, ion exchange membranes are successfully applied for water and energy for different electro-membrane processes. Hydrogen could be produced by electrochemical water splitting using renewable energy, for example, solar, biomass, geothermal and wind energy. This review briefly summarizes the recent studies reporting the state-of-the-art anion-exchange membrane water electrolysis, especially focusing on the enhancement of the durability of anion-exchange membranes. Anion-exchange membrane water electrolysis could be used as inexpensive non-noble metal electrocatalysts that are capable of producing low cost of hydrogen. However, the main challenge of anion-exchange membrane water electrolysis is to increase the performance and durability. In this mini review, the limiting factors of the durability and the technology enhancing the durability will be discussed for anion exchange membrane water electrolysis.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.2
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• pp.226-234
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• 2018

Even though the nuclear power plants has many advantages, safety issues of nuclear power plants are crucial factors of reliable operation. A tritium detector is a useful sensor to analyze amount of exposed radiation from the nuclear power plants. Currently, concentration of underwater tritium is measured precisely but it takes very long time. Since electrolysis is extracted hydrogen from the coolant of nuclear power plant, it can motivate to develop new type of real-time sensor. In this study, Proton Exchange Membrane (PEM) electrolyzer is studied for candidate as preprocessor of real-time tritium detector. Characteristics of the unit PEM electrolyzer were experimentally investigated. A simulation model is developed to understand physical behavior of unit PEM electrolyzer under dynamic operation.

• BMB Reports
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• v.41 no.1
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• pp.35-40
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• 2008

The molten globular conformation of V26A ubiquitin (valine to alanine mutation at residue 26) was studied by nuclear magnetic resonance spectroscopy in conjunction with amide hydrogen/deuterium exchange. Most of the amide protons that are involved in the native secondary structures were observed to be protected in the molten globule state with the protection factors from 1.2 to 6.7. These protection factors are about 2 to 6 orders of magnitude smaller than those of the native state. These observations indicate that V26A molten globule has native-like backbone structure with marginal stability. The comparison of amide protection factors of V26A ubiquitin molten globule state with those of initial collapsed state of the wild type ubiquitin suggests that V26A ubiquitin molten globule state is located close to unfolded state in the folding reaction coordinate. It is considered that V26A ubiquitin molten globule is useful model to study early events in protein folding reaction.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.410-415
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• 1996

It is well known that the heavy water separation process using hydrogen isotope exchange reaction over the platinum catalyst is the most efficient. In this study, the Pt/silicalite catalysts were prepared and characterized by hydrogen adsorption in order to develop the hydrophobic platinum catalyst for hydrogen isotope exchange reaction. Silicalite was synthesized as support material and it was verified that silicalite is more hydrophobic than activated carbon and ZSM-5. Also the platinum was loaded on silicalite by conventional impregnation and ion-exchange method respectively. The platinum dispersion of Pt/silicalite catalysts was measured through hydrogen adsorption experiment. The dispersion is very low in the catalyst prepared by the impregnation method while it is very high with limited platinum content in the catalyst prepared by the ion-exchange method.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.3
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• pp.209-218
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• 2022

Recently, research on the development of anion exchange membranes (AEMs) has received considerable attention from the scientific community around the world. Here, we fabricated a series of AEMs with branched structures with different alkyl spacers and conducted comparative evaluations. The introduction of these branched structures is an attempt to overcome the low ionic conductivity and stability problems that AEMs are currently facing. To this end, branched polymers with different spacer lengths were synthesized and properties of each membrane prepared according to the branched structure were compared. The chemical structure of the polymer was investigated by proton nuclear magnetic resonance, Fourier transform infrared, and gel permeation chromatography, and the thermal properties were investigated using thermogravimetric analysis. The branched anion exchange membrane with (CH₂)₃ and (CH₂)₆ spacers exhibited ionic conductivities of 8.9 mS cm^-1 and 22 mS cm^-1 at 90℃, respectively. This means that the length of the spacer affects the ionic conductivity. Therefore, this study showing the effect of the spacer length on the ionic conductivity of the membrane in the polymer structure constituting the ion exchange membrane is judged to be very useful for future application studies of AEM fuel cells.

• Journal of the Korean Magnetic Resonance Society
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• v.23 no.3
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• pp.61-66
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• 2019

RNAs exhibit distinct structural and dynamic features required for proper function. The hydrogen-bonded imino protons of RNAs are a probe of the conformational transition and dynamic feature. MicroRNAs originate from primary transcripts containing hairpin structures. The levels of mature miR156 influence the flowering time of plants. To understand the molecular mechanism of biological function of $miR156:miR156^*$ duplex, we performed hydrogen exchange study on the model RNAs mimicking two phenotypes of $miR156:miR156^*$, $miR156:miR156^*$ (m-miR156a) and $miR156:miR156^*$ (m-miR156g) duplexes. This study found that the internal bulge of m-miR156a destabilized the neighboring base-pairs, whereas the bulge structure of m-miR156g did not affect the thermal stabilities of the neighboring base-pairs.