• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.135-141
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• 2020

Although the graphene is regarded as a promising material for the electrode of the supercapacitor, its electrochemical performance is still less enough to satisfy the current demand raised in real applications. Here, using a home laser engraver, firstly we performed the prompt and selective reduction of the graphene oxide to produce multilayered and highly porous graphene maintaining high electrical conductivity. Subsequently, the resulting graphene was conformally deposited with pseudocapacitive thin VO_x using atomic layer deposition in order to enhance specific capacitance of graphene. We observed that various forms of VO_x exist in the VO_x/graphene hybrid through XPS analysis. The hybrid showed highly improved specific capacitance (~189 F/g) as compared to the graphene without VO_x. We expect that our approach is accepted as one of the alternatives to produce the graphene-based electrode for various energy storage devices.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.359-366
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• 2002

The purpose of this study is to investigate the properties of LSGM electrolyte and LSM cathode. The unit cell based on the optimum conditions and processing for high performance was fabricated and measured. The single phase of $LaGaO_3$ was obtained on sintering at $1500^{\circ}$ for 6h with composition of $(La_{0.85}Sr_{0.15})(Ga_{0.8}Mg_{0.2})O_{3-\delta}와 (La_{0.8}Sr_{0.2})(Ga_{0.8}Mg_{0.2})O_{3-\delta}$ and $(La_{0.85}Sr_{0.15})(Ga_{0.8}Mg_{0.2})O_{3-\delta}$. The grain size of the sintered body was about $10∼30{\mu}m$ and electrical conductivity was 0.13 S/cm measured at $800^{\circ}$. The single phase of $LaMnO_3$ structure in $(La1-xSrx)MnO_3$ system was obtained at x=0∼0.2 and the particle size of the synthesized powder was about 40 nm. The unit cell was prepared by firing at $1200^{\circ}$ for 1h with $(La_{0.9}Sr_{0.1})MnO_3$ cathode and 0.9NiO-0.1YSZ anode screen-printed on surfaces of $(La_{0.8}Sr_{0.2})(Ga_{0.8}Mg_{0.2})O_{3-\delta}$ electrolyte. The grain size of the electrode was close to $1{\mu}m$ and the electrode had porous structure. The maximum power density of unit cell showed $0.3W/cm^2$ at $800^{\circ}$.

• Composites Research
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• v.35 no.6
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• pp.394-401
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• 2022

Two polymer precursors, polyvinylidene chloride-resin (PVDC-resin) and polyvinylidene fluoride (PVDF), are assembled into the microporous carbon by pyrolysis. Microporous carbon is advantageous as an electrode for supercapacitors that store electric charges through ion adsorption/desorption. The pyrolysis also turns the various heteroatoms of two precursors into functional groups, contributing to the additional charge storage. The analysis of the porous structure and function group during carbonization are important to develop the carbon for energy storage. Here, we analyzed the functional groups of two polymer-derived carbons through X-ray photoelectron spectroscopy. The electrochemical properties of the functional groups were explored in various pH electrolytes. The specific capacitance of two carbons in the acidic electrolyte (1 M H₂SO₄) was improved compared to that in the neutral electrolyte (0.5 M Na₂SO₄) due to the faradaic charge/discharge reaction of the quinone functional group. In particular, the carbon electrode derived from PVDC-resin exhibits a lower capacity than the carbon from PVDF due to the small micropores. In the alkaline electrolyte (6 M KOH), the highest specific capacitance and rate capability were obtained among the three electrolytes for both electrodes based on the facile adsorption of the constituent electrolyte ions (K⁺, OH^-).

• Journal of the Korean Electrochemical Society
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• v.25 no.4
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• pp.174-183
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• 2022

Polymer electrolyte fuel cells and water electrolysis are attracting attention in terms of high energy density and high purity hydrogen production. The catalyst layer for the polymer electrolyte fuel cell and water electrolysis is a porous electrode composed of a precious metal-based electrocatalyst and an ionomer binder. Among them, the ionomer binder plays an important role in the formation of a three-dimensional network for ion conduction in the catalyst layer and the formation of pores for the movement of materials required or generated for the electrode reaction. In terms of the use of commercial perfluorinated ionomers, the content of the ionomer, the physical properties of the ionomer, and the type of the dispersing solvent system greatly determine the performance and durability of the catalyst layer. Until now, many studies have been reported on the method of using an ionomer for the catalyst layer for polymer electrolyte fuel cells. This review summarizes the research results on the use of ionomer binders in the fuel cell aspect reported so far, and aims to provide useful information for the research on the ionomer binder for the catalyst layer, which is one of the key elements of polymer electrolyte water electrolysis to accelerate the hydrogen economy era.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.303-308
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• 2024

Currently, lithium secondary batteries have been used as medium- or large-sized energy sources such as electric vehicles and energy storage system (ESS) due to their high energy and eco-friendly characteristics. Currently commercialized lithium secondary batteries do not fully meet the demands for high energy density and safety. Many studies on solid electrolytes are being conducted to satisfy these requirements. In order to commercialize a solid electrolyte, it is important to supplement the low ion conductivity and high interface resistance with an electrode compared to the organic liquid electrolyte. Therefore, in this study, oligo(3,4-ethylenedioxythiophene (EDOT)) is added to poly(vinyl alcohol) (PVA), which is a polymer matrix with ion conductivity and sticky characteristics, to decrease the interfacial resistance with the same type of polythiophene (PTh)-based electrode. In addition, the addition of porous silicon dioxide (SiO₂) filler improves lithium salt dissociation ability and increases ionic conductivity. And the electrochemical stability of the solid electrolyte, which has been lowered due to additives, is improved by introducing a cross-linked structure using boric acid (BA).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.157-163
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• 2010

Solid oxide fuel cells (SOFCs) are commonly composed of ceramic compartments, and it is known that the physical properties of the ceramic materials can be changed according to the operating temperature. Thus, the physical properties of the ceramic materials have to be properly predicted to develop a highly reliable simulation model. In this study, several physical properties that can affect the performance of SOFCs were selected, and simulation models for those physical properties were developed using our own code. The Gibbs free energy for the open circuit voltage, exchange current densities for the activation polarization, and electrical conductivity for the electrolyte were calculated. In addition, the diffusion coefficient-including the binary and Knudsen diffusion mechanisms-was calculated for mass transport analysis at the porous electrode. The physical property and electrochemical reaction models were then simulated simultaneously. The numerical results were compared with the experimental results and previous works studied by Chan et al. for code validation.

• Polymer(Korea)
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• v.36 no.6
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• pp.739-744
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• 2012

In this work, we prepared the carbons from synthesized styrene-acrylonitrile carbon precursor. The prepared carbons were chemically activated, and then the activated SAN-based carbons were named as A-SANs. The activations were carried out at different temperatures to investigate the effect of activation temperature on the surface and electrochemical properties of the activated SAN-based carbons for using as an electrode of electric double layer capacitors (EDLC). The characteristics of A-SAN were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area and pore size analysis. Also, the electrochemical behaviors were observed by cyclic voltammetry and galvanostatic charge-discharge method. From the results, the A-SAN 700 showed excellent electrochemical property and the highest specific capacitance, but these properties decreased when the activation temperature was above $700^{\circ}C$. This is due to the fact that the activation at a temperature over $700^{\circ}C$ causes deformation of micropore structures.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.3
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• pp.245-251
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• 2014

Pyroprocess for treating spent nuclear fuels has been developed based on electrochemical principles. Process simulation is one of the important methods for process development and experimental data analysis and it is also a necessary approach for pyroprocessing. To date, process simulation of pyroprocessing has been focused on electrorefining and there have been not so many investigations on electrolytic reduction. Electrolytic reduction, unlike electrorefining, includes specific features of gas evolution and porous electrode and, thus, different equations should be considered for developing a model for the process. This study summarized required concepts and equations for electrolytic reduction model development from thermodynamic, mass transport, and reaction kinetics theories which are necessitated for analyzing an electrochemical cell. An electrolytic reduction cell was divided and equations for each section were listed and, then, boundary conditions for connecting the sections were indicated. It is expected that those equations would be used as a basis to develop a simulation model for the future and applied to determine parameters associated with experimental data.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.495-499
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• 2010

The biocatalytic capture of $CO_2$, and its precipitationas $CaCO_3$, over bovine carbonic anhydrase (BCA) immobilized on a pore-expanded SBA-15 support was investigated. SBA-15 was synthesized using TMB as a pore expander, and the resulting porous silica was characterized by XRD, BET, IR, and FE-SEM analysis. BCA was immobilized on SBA-15 through various approaches, including covalent attachment (BCA-CA), adsorption (BCA-ADS), and cross-linked enzyme aggregation (BCA-CLEA). The immobilization of BCA on SBA-15 was confirmed by the presence of zinc metal in the EDXS analysis. The effects of pH, temperature, storage stability, and reusability on the biocatalytic performance of BCA were characterized by examining para-nitrophenyl acetate (p-NPA) hydrolysis. The $K_{cat}/K_m$ values for p-NPA hydrolysis were 740.05, 660.62, and $680.11M^{-1}s^{-1}$, respectively, where as $K_{cat}/K_m$ for free BCA was $873.76M^{-1}s^{-1}$. The amount of $CaCO_3$ precipitate was measured quantitatively using anion-selective electrode and was found to be 12.41, 11.82, or 11.28 mg $CaCO_3$/mg for BCA-CLEA, BCA-ADS, or BCA-CA, respectively. The present results indicate that the immobilized BCA-CLEA, BCA-ADS, and BCA-CA are green materials, and are tunable, reusable, and promising biocatalysts for $CO_2$ sequestration.

• Membrane Journal
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• v.25 no.1
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• pp.60-66
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• 2015

To investigate the performance of the composite carbon electrodes which the ion exchange polymers were directly casted onto porous carbon electrode surfaces, the adsorption/desorption experiments were carried out by varying the feed concentration, feed flow rate, and desorption voltages for the NaCl solution. When the feed concentration was 100 mg/L, the increase of the adsorption time led to the increase of the salt removal due to the increase of the residence time inside the cell while the increase of the feed flow rate from 15 mL/min to 23 mL/min gave the decrease of the salt removal efficiency, 12% because of the short residence time. When the feed concentration was 200 mg/L, the salt removal was shown 10~15% low because of the incomplete desorption within the desorption intervals.