• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.139-147
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• 2019

Lithium-ion battery (LiB) with high energy density and efficiency has been utilized for the electric vehicle (EV) and energy storage system (ESS) as well as portable devices. However, as explosion accidents have frequently happened till lately, all-solid-state lithium secondary battery (ALSB) began to get in a spotlight because it can secure a very high safety and energy density by substituting flammable organic liquid electrolyte to nonflammable inorganic solid electrolyte. In spite of ALSB's certain merits, it has shown much poorer performance of cells than one of LiB due to some challenges, which have been small or never dealt with in the LiB system. Hence, although plenty of studies made progress to solve them, an approach about design of all-solid-state electrode (ASSE) has been limited on account of difficulty of ALSB's experiments. That is why the virtual 3D structure of an all-solid-state electrode has to be built and used for the prediction of cell performance. In this study, we elucidate how to form the 3D ASSE structure and what to be needed for the simulation of characteristics on ALSB. Furthermore, the ultimate orientation of 3D modeling and simulation for the study of ALSB are briefly suggested.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.5
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• pp.196-201
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• 2023

In order to improve the efficiency of the water splitting system for hydrogen energy production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds (hydroxide, sulfide, etc.) are attracting attention as catalyst materials to replace currently used precious metals such as platinum. In this study, Ni foam, an inexpensive metal porous material, was used as a support and β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, changes in the crystal morphology, crystal structure, and water splitting characteristics of β-Ni(OH)₂ microcrystals synthesized by doping Fe to improve electrochemical properties were observed, and applicability as a catalyst in a commercial water electrolysis system was examined.

• Journal of the Korean Chemical Society
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• v.50 no.6
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• pp.454-463
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• 2006

refractory organic compounds in aqueous solution are not readily removed by the existing conventional wastewater treatment process. In recent years, the sonolysis and electrochemical oxidation process had been shown to be promising for wastewater treatment due to the effectiveness and easiness in operation. This study was performed to investigate the characteristics of sonolytic and electrolytic decomposition as the basic data for development of the wastewater treatment process. Trichloroethylene(TCE) and 2,4- dichlorophenol(2,4-DCP) were used as the samples, and their destruction efficiency were measured with various operating parameters, such as initial solution concentration, initial solution pH, reaction temperature, sonic power and current density. Also, the decomposition mechanism conformed indirectly with the effect of NaHCO3 as a radical scavenger on the decomposition reaction. Thermal decompositon reaction is predominant for TCE but thermal and radical decompositon reactions were dominant for 2,4-DCP. Results showed that the destruction efficiencies of all samples were above 65% within 120 minutes by sonolysis and electrolysis at the same time, and were increased with increasing initial concentration, sonic power and current density. Destruction efficiency of TCE was high in the acidic solution, but 2,4-DCP showed high destruction efficiency in basic solution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5728-5735
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• 2015

This study attempts to verify the applicability of ceramic membrane as a separator by comparing the power generation characteristics in single-chamber MFCs using ceramic membranes to those in the MFCs using nafion membrane. The generated power in MFCs by using acetate as a substrate was more stable than that by using formate, propionate and butyrate, respectively. It was shown that the generated power by using formate substrate in MFCs was unstable and a little higher than that by using acetate, and the power generated by using propionate and butyrate were lower than that by using acetate. In order to find out the Pt catalyst effect, it was compared the power generated in MFCs using Pt-coated carbon cloth as electrode to that power using normal carbon cloth. The power generated in MFCs using Pt-coated carbon cloth as electrode was 1.2 times higher than that using normal carbon cloth. The Pt-coated carbon cloth was about 5 times more expensive than normal carbon cloth. It is suggested that both power generation efficiency and cost together should be considered in selecting electrodes of MFCs. It was found that the ceramic membrane was superior to nafion membrane by comparing to the power generation characteristics obtained. It was shown that average voltage values were $523.67mV{\pm}49.41mV$ by using synthetic wastewater, in MFCs of ceramic membrane as a separator. While average voltage values were $424.09mV{\pm}79.95mV$ by using synthetic wastewater, in MFCs of nafion membrane as a separator. The organic removal efficiency, 41.7% by using ceramic membrane was a little bit higher than 40.8% by using nafion membrane. This research implies ceramic membrane can be a valid alternative to nafion membrane as a separator when considering the power generation and the efficiency of organics removal.

• Clean Technology
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• v.9 no.3
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• pp.133-144
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• 2003

In this study, Insoluble catalyst electrode for oxide systems were manufactured, by using of them, carried out experiments on electrolytic treatment of dyeing wastewater containing persistent organic compounds, and then made a comparative study of the efficiency of treatment for environmental pollutants and whether each of them is valuable of not as an electrode for soluble electrode(Fe, Al) and insoluble electrode(SUS, R.C.E; Replaced Catalyst Electrode) which were used in the electrolytic system. Besides, it was investigated the conditions for electrolytic treatment to find the maximum efficiency of electrolytic treatment. As the result of this study, by using of insoluble catalyst electrode for oxide can solved the stability of electrode that is one of the greatest problems in order to put to practical use of electrolysis process in the treatment of the sewage and wastewater and the result runs as follows; 1. The durability of insoluble catalyst electrode(R.C.E) can be verified the most favorable when the molar ratio of $RuO_2-SnO_2-IrO_2-TiO_2$(4 compounds system) is 70/20/5/5. 2. The efficiency of treatment was obtained a more than 90% goodness for CODMn and also a good results for T-N removal in the experimental conditions of the distance of electrode 5 mm, time of electrolysis 60 minutes, permissible voltage 10V, processing capacity $0.5{\ell}$.

• Journal of Wetlands Research
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• v.20 no.3
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• pp.263-271
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• 2018

In this study, we analyzed the removal efficiency of ammonia nitrogen and phosphate dependant on the column depths using various absorbents such as zeolite silica sand, and activated carbon through the column test. In addition, we analyzed electrochemical adsorption behaviors of ammonia nitrogen and phosphate through the quantum mechanical calculation based on density functional theory calculation. Experimental results represent the removal efficiency of ammonia nitrogen and phosphate are zeolite > activated carbon > silica sand, and activated carbon > zeolite > silica sand, respectively. Zeolite shows high adsorption property for ammonia nitrogen over 90%, regardless of the column depth, while activated carbon exhibits high adsorption property for both ammonia nitrogen and phosphate as the column depth for filter media increases. Theoretical findings using DFT calculation for the adsorption behaviors of adsorbents (activated carbon and silica sand) and nutrients ($PO_4{^{3-}}$, $NH_4{^{+}}$) show that activated carbon represented narrower HOMO-LUMO band gap with high adsorption energy, and even more favorable environment for electron adsorption than silica sand, which leads to the effective removal of nutrients.

• Clean Technology
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• v.27 no.3
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• pp.223-231
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• 2021

In order to address many issues associated with large volume changes of silicon, which has very low electrical conductivity but offers about 10 times higher theoretical capacity than graphite (Gr), a silicon nanoparticles/hollow carbon (SiNP/HC) composite having bimodal-mesopores was prepared using silica nanoparticles as a template. A control SiNP/C composite without a hollow structure was also prepared for comparison. The physico-chemical and electrochemical properties of SiNP/HC were analyzed by X-ray diffractometry, X-ray photoelectron spectroscopy, nitrogen adsorption/desorption measurements for surface area and pore size distribution, scanning electron microscopy, transmission electron microscopy, galvanostatic cycling, and cyclic voltammetry tests to compare them with those of the SiNP/C composite. The SiNP/HC composite showed significantly better cycle life and efficiency than the SiNP/C, with minimal increase in electrode thickness after long cycles. A hybrid composite, SiNP/HC@Gr, prepared by physical mixing of the SiNP/HC and Gr at a 50:50 weight ratio, exhibited even better cycle life and efficiency than the SiNP/HC at low capacity. Thus, silicon/carbon composites designed to have hollow spaces capable of accommodating volume expansion were found to be highly effective for long cycle life of silicon-based composites. However, further study is required to improve the low initial coulombic efficiency of SiNP/HC and SiNP/HC@Gr, which is possibly because of their high surface area causing excessive electrolyte decomposition for the formation of solid-electrolyte-interface layers.

• Journal of Adhesion and Interface
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• v.22 no.1
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• pp.1-7
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• 2021

The importance of high capacity energy storage devices has recently emerged for stable power supply through renewable energy generation. From this point of view, the Na-air battery (NAB), which is a next-generation secondary battery, is receiving huge attention because it can realize a high capacity through abundant and inexpensive raw materials. In this study, activated carbon-based catalysts for hybrid type Na-air batteries were prepared and their characteristics were compared and analysed. In particular, from the viewpoint of resource recycling, activated carbon (Orange-C) was prepared using discarded orange peel, and performance was compared with Vulcan carbon, which is widely used. In addition, a Pt/C catalyst (homemade-Pt/C, HM-Pt/C) was synthesized using a modified polyol method to check whether the prepared activated carbon can be used as a supported catalyst, and a commercial Pt/C catalyst (Commercial Pt/C) and electrochemical performance were compared. The prepared Orange-C exhibited a typical H3 type BET isotherm, which is evidence that micropore and mesopore exist. In addition, in the case of HM-Pt/C, it was confirmed through TEM analysis that Pt particles were evenly distributed on the activated carbon supported catalyst. In particular, the HM-Pt/C-based NAB showed the smallest voltage gap (0.224V) and good voltage efficiency (92.34%) in the 1st galvanostatic charge-discharge test. In addition, the cycle performance test conducted for 20 cycles showed the most stable performance.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.487-496
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• 2014

In this study, three kinds of polymers based on phenothiazine-benzothiadiazole were synthesized by a Suzuki coupling reaction, and the various side-chains were substituted at the nitrogen of phenothiazine. The optical and electrochemical properties of synthesized polymers were analyzed. The results indicate that their absorption ranged from 300 to 700 nm, and also confirmed the ideal highest occupied molecular orbital (HOMO) energy level was about -5.4 eV with low band-gap energy. Photovoltaic devices were fabricated using a photoactive layer composed of a blended solution of the polymer and $PC_{71}BM$ in ortho-dichlorobenzene The device with P2HDPZ-bTP-OBT containing the branched side-chain and long chain showed the best performance; the maximum power conversion efficiency of this device was 2.4% (with $V_{OC}$ : 0.74 V, $J_{SC}$ : $6.9mA/cm^2$, FF : 48.0%).

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.531-539
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• 2015

Chlor-alkali industry is one of the largest electrochemical processes which annually producing 70 million tons of sodium hydroxide and chlorine from sodium chloride solution. $DSA^{(R)}$ (Dimensionally Stable Anodes) electrodes such as $RuO_2$ and $IrO_2$, which is popular in chlor-alkali process, have been investigated to improve the chlorine generation efficiency. Although DSA electrode has been developed with various researches, understanding of the chlorine evolution mechanism is essential to the development of highly efficient DSA electrode. In this review paper, chlorine generation mechanisms are summarized and that of key factors are identified to systematically understand the chlorine generation mechanism. Rate determining step, effect of pH, reaction intermediate, and electrode crystal structure were intensively overviewed as key factors of the chlorine mechanism.