• Journal of Environmental Science International
• /
• v.11 no.5
• /
• pp.437-443
• /
• 2002

The chemical behavior and properties of the redox state of environmental pollutants were investigated using electrochemical methods. Cyclic voltammograms were performed on the compounds to measure the variations in the redox reactions. Temperature and pH were established as influencing the redox potential and current. The electrode reactions were a mixture of quasi-reversible and irreversible Precesses, which changed according to the reaction current. Although the Co(BPA)$_2$ and Cu(BPA)$_2$ compounds were not found to dissociate in wastewater, they were very unstable(K=1.02).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.4 s.235
• /
• pp.477-484
• /
• 2005

Model fer the dynamic simulation of dynamic behaviors of a solid oxide fuel cell (SOFC) is provided. This model is based upon (1) coupled mass and heat transfer characteristics and (2) important chemical reactions such as electrochemical and reforming reactions in high temperature fuel cells such as SOFC. It is found that the thermal inertia of solid materials in SOFC plays an important role to the dynamic behavior of cell temperature. Dynamic characteristics of cell voltage, power, and chemical compositions with different levels of load change are investigated.

• Electronics and Telecommunications Trends
• /
• v.38 no.5
• /
• pp.90-99
• /
• 2023

Recently, with the trend of information technology convergence and electrification, batteries are being widely used in fields such as industry, transportation, and specific applications. By 2030, the secondary battery market is expected to grow explosively by more than eight times compared with 2020 to $351.7 billion owing to the expanding adoption of electric vehicles. Depending on the electrochemical reactions in the electrode, a primary battery can only discharge through an irreversible reaction, while a secondary battery can be repeatedly charged and discharged using reversible reactions. According to the type of charge carrier ions, secondary batteries may be classified into those made of lithium, sodium, potassium, magnesium, and aluminum ions. We analyze the current status and technological issues of lithium-ion batteries, lithium-sulfur batteries, and solid-state batteries, which are representative examples of lithium secondary batteries. In addition, research trends in lithium secondary batteries are discussed.

• Journal of the Korean Chemical Society
• /
• v.68 no.2
• /
• pp.87-92
• /
• 2024

The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.9
• /
• pp.1329-1334
• /
• 2006

The electrochemical reduction of coumarin, 7-acetoxy-4-methyl coumarin (AMC), and 7-acetoxy-4-bromomethyl coumarin (ABMC), in 0.1 M tetraethyl ammonium perchlorate/acetonitrile solution was carried out by direct current, differential pulse polarography, cyclic voltammetry, and controlled potential coulometry. The electrochemical reduction of ABMC was proceeded through three steps of electron transfer coupled with the chemical reactions. The color of solution was changed to yellow when the carbonyl group was reduced during 2nd step (-1.8 volts) and independented with cleavage of bromo group. Highest fluorescence intensity showed when the electrochemical reduction of AMC was controlled at near the potential (-2.3 volts vs. Ag/AgCl).

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.95.2-95.2
• /
• 2011

In order to achieve high performance and low cost for commercial applications, the development of membrane electrode assemblies (MEA), in which the electrochemical reactions actually occur, must be optimized. Expensive platinum is currently used as an electrochemical catalyst due to its high activity. Although various platinum alloys and non-platinum catalysts are under development, their stabilities and catalytic activities, especially in terms of the oxygen reduction (ORR), render them currently unsuitable for practical use. Therefore, it is important to decrease platinum loading by optimizing the catalysts and electrode microstructure. In this study, we prepared several different MEAs (non-uniform Nafion$^{(R)}$ ionomer loading electrode) which have dual catalyst layers to find the optimal Nafion$^{(R)}$ ionomer distribution in the electrodes. We changed Nafion$^{(R)}$ ionomer content in the layers to find the ideal composition of the binder and Pt/C in the electrode. For MEAs with various ionomer contents in the anodes and cathodes, the electrochemical activity (activation overpotential) and the mass transport properties (concentration overpotential) were analyzed and correlated with the single cell performance. The dual catalyst layers MEA showed higher cell performance than uniformly fabricated MEA, especially at the high current density region.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.18 no.2
• /
• pp.143-155
• /
• 2020

A reference electrode is important for controlling electrochemical reactions. Evaluating properties such as the reduction potential of the elements is necessary to optimize the electrochemical processes in pyroprocessing, especially in a multicomponent environment. In molten chloride systems, which are widely used in pyroprocessing, a reference electrode is made by enclosing the silver wire and molten salt solution containing silver chloride into the membranes. However, owing to the high temperature of the molten salt, the choice of the membrane for the reference electrode is limited. In this study, three types of electroceramic, mullite, Pyrex, and quartz, were compared as reference electrode membranes. They are widely used in molten salt electrochemical processes. The potential measurements between the two reference electrode systems showed that the mullite membrane has potential deviations of approximately 50 mV or less at temperatures higher than 650℃, Pyrex at temperatures lower than 500℃, and quartz at temperatures higher than 800℃. Cyclic voltammograms with different membranes showed a significant potential shift when different membranes were utilized. This research demonstrated the uncertainties of potential measurement by a single membrane and the potential shift that occurs because of the use of different membranes.

• Journal of the Korean Electrochemical Society
• /
• v.4 no.1
• /
• pp.21-25
• /
• 2001

This article is concerned with the application of the fractal geometry to interfacial electrochemistry. Especially, we dealt with diffusion kinetics at the fractal electrodes. This article first explained the basic concepts of the Sacral geometry which has proven to be fruitful for modelling rough and irregular surfaces. Finally this article examined the electrochemical responses to various signals under diffusion-limited reactions during diffusion towards the fractal interfaces: The generalised forms, including the fractal dimension of the electrode surfaces, of Cottrell, Sand and Randles-Sevcik equations were theoretically derived and explained in chronoamperomety, chronopotentiometry and linear sweep/cyclic voltammetry, respectively.

• Applied Chemistry for Engineering
• /
• v.24 no.4
• /
• pp.337-343
• /
• 2013

Membrane reactors have been showing a promising future and attracted increasing attention in the scientific community as they possess advantages in terms of enhanced catalytic activity and selectivity, combination of processes (reaction and separation), simplicity in process design, and safety in operation. In particular, solid electrolyte membrane reactor principles are realized in fuel cells, electrolyzers and reactors for hydrogenation of carbon dioxide and other economically viable reactions. In this review, as a young generation of ion conducting materials, high temperature proton conductors are discussed in terms of the current status of material development and their various applications.

• Journal of the Korean Ceramic Society
• /
• v.42 no.12 s.283
• /
• pp.787-792
• /
• 2005

A symmetrical LSCF $(La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta})\;ScSZ(89ZrO_2-10Sc_2O_3-1CeO_2)/LSCF$ electrochemical cell with a GDC (Gadolinium-Doped Ceria, $90CeO_2-10Gd_2O_3$) interlayer that was inserted between the LSCF cathode and ScSZ electrolyte was fabricated, and the electrochemical performance of these cells was evaluated. The GDC interlayer was deposited on a ScSZ electrolyte using a screen-printing technique. The GDC interlayer prevented the unfavorable solid-state reactions at the LSCF/ScSZ interfaces. The LSCF cathode on the GDC interlayer had excellent electrocatalytic performance even at $650^{\circ}C$. The Area Specific Resistance (ASR) was strongly dependent on the thickness and heat-treatment temperature of the GDC interlayer. The impedance spectra showed that the cell with a $15\~27{\mu}m$ thick GDC interlayer heat-treated at $1200^{\circ}C$ had the lowest ASR.