• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.781-786
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• 1996

Mass transport behavior of C60 films on electrodes with different thicknesses has been studied by an Electrochemical Quartz Crystal Microbalance (EQCM) during electrochemical reduction-oxidation processes in the presence of water. C60 films were found to be reduced in the presence of water and they remains quite stable. In thin films, the mass on electrode decreased after a complete cycle while X-ray Photoelectron Spectroscopy (XPS) study does not support the existence or formation of C60-epoxides during electrochemical reduction processes in the presence of water or oxygen.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.126-136
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• 2021

The electrochemical performance of all-solid-state cells (ASSCs) based on sulfide electrolytes is critically affected by the undesirable interfacial reactions between oxide cathodes and sulfide electrolytes because of the high reactivity of sulfide electrolytes. Based on the concept that the interfacial reactions are highly dependent on the type of sulfide electrolyte, the electrochemical properties of the ASSCs prepared using three types of sulfide electrolytes were observed and compared. The Li2MoO4-LiI coating layer was also introduced to suppress the interfacial reactions. The cells using argyrodite electrolyte exhibited a higher capacity and Coulombic efficiency than the cells using 75Li2S-22P2S5-3Li2SO4 and Li7P3S11 electrolytes, indicating that the argyrodite electrolyte is less reactive with cathodes than other electrolytes. Moreover, the introduction of Li2MoO4-LiI coating on the cathode surface significantly enhanced the electrochemical performance of ASSCs because of the protection of coating layer. Pulverization of argyrodite electrolyte is also effective in increasing the capacity of cells because the smaller size of electrolyte particles improved the contact stability between the cathode and the sulfide electrolyte. The cyclic performance of cells was also enhanced by pulverized electrolyte, which is also associated with improved contact stability at the cathode/electrolyte. These results show that the introduction of Li2MoO4-LiI coating and the use of pulverized sulfide electrolyte can exhibit a synergic effect of suppressed interfacial reaction by the coating layer and improved contact stability owing to the small particle size of electrolyte.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.98.2-98.2
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• 2013

Electrochemical phenomena underpin a broad spectrum of energy, chemical, and information technologies such as resistive memories and secondary batteries. The optimization of functionalities in these devices requires understanding electrochemical mechanisms on the nanoscale. Even though the nanoscale electrochemical phenomena have been studied by electron microscopies, these methods are limited for analyzing dynamic electrochemical behavior and there is still lack of information on the nanoscale electrochemical mechanisms. The alternative way can be an atomic force microscopy (AFM) because AFM allows nanoscale measurements and, furthermore, electrochemical reaction can be controlled by an application of electric field through AFM tip. Here, I will summarize recent studies to probe nanoscale electrochemical reaction in battery applications by AFM. In particular, we have recently developed electromechanical based AFM techniques for exploring reversible and irreversible electrochemical phenomena on the nanoscale. The present work suggests new strategies to explore fundamental electrochemical mechanisms using the AFM approach and eventually will provide a powerful paradigm for probing spatially resolved electrochemical information for energy applications.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.14-25
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• 2020

Li ion battery (LIB) is one of the most remarkable energy storage devices currently available in various applications. With a growing demand for high-performance batteries, the role of electrochemical analysis for batteries, especially, electrode reactions are becoming very important and crucial. Among various analytical methods, cyclic voltammetry (CV) is very versatile and widely used in many fields of electrochemistry. Through CV, it is possible to know electrochemical factors affecting the reaction voltage and reversibility, and furthermore, quantitative analysis on Li⁺ diffusivity as well as intercalation and capacitive reactions, and also anionic redox reaction. However, the explanation or interpretation of the results of CV is often deficient or controversial. In this mini-review, we briefly introduce the principle of cyclic voltammetry and its applications in LIB to bring a better understanding of the electrochemical reaction mechanisms involved in LIB.

• Corrosion Science and Technology
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• v.16 no.2
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• pp.59-63
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• 2017

Chelating solutions can be damaged by strong acids during oil production. To design effective corrosion inhibitors and other alternatives for corrosion control, it is important to understand not only the behavior of the system under operating condition but also the kinetics of electrochemical reactions during the corrosion process. In this study, the electrochemical behaviors of P-110 steel in aqueous fluids based on ethylenediaminetetraacetic acid (EDTA) compounds under various temperatures and hydrodynamic regime conditions were assessed. Electrochemical measurements were conducted using rotating disc electrodes manufactured. Electrolytes were prepared using aqueous compounds of EDTA like diammonium salt, disodium salt, and tetrasodium salt. Potentiodynamic polarization, electrochemical impedance, and mass loss tests were performed in order to assess the corrosion kinetic in electrolytes. Hydrodynamic effects were observed only in the cathodic polarization curve. This proves that hydrodynamic regime plays an important role in the corrosion of steel mainly in disodium and diammonium EDTA solutions. Two cathodic reactions controlled the corrosion process. However, oxygen level and pH of the electrolyte played the most important role in metal corrosion. Corrosion rates in those fluids were decreased drastically when oxygen concentration was reduced.

• Journal of Electrochemical Science and Technology
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• v.14 no.3
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• pp.231-242
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• 2023

Li₂O-based cathodes utilizing oxide-peroxide conversion are innovative next-generation cathodes that have the potential to surpass the capacity of current commercial cathodes. However, these cathodes are exposed to severe cathode-electrolyte side reactions owing to the formation of highly reactive superoxides (O^x-, 1 ≤ x < 2) from O^2- ions in the Li₂O structure during charging. Succinonitrile (SN) has been used as a stabilizer at the cathode/electrolyte interface to mitigate cathode-electrolyte side reactions. SN forms a protective layer through decomposition during cycling, potentially reducing unwanted side reactions at the interface. In this study, a composite of Li₂O and Ni-embedded reduced graphene oxide (LNGO) was used as the Li₂O-based cathode. The addition of SN effectively thinned the interfacial layer formed during cycling. The presence of a N-derived layer resulting from the decomposition of SN was observed after cycling, potentially suppressing the formation of undesirable reaction products and the growth of the interfacial layer. The cell with the SN additive exhibited an enhanced electrochemical performance, including increased usable capacity and improved cyclic performance. The results confirm that incorporating the SN additive effectively stabilizes the cathode-electrolyte interface in Li₂O-based cathodes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.395-396
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• 2005

We fabricated self-assembled monolayers(SAMs) onto quartz crystal microbalance(QCM) using viologen, which has been widely used as electron acceptor and electron transfer mediator. We determined the time dependence to resonant frequency shift during self-assembly process and observed the morphology of self-assembled mono layers by STM and investigated the electrochemical behavior of SAMs by cyclic voltammetry. Electrochemical deposition of viologen was investigated using electrochemical quartz crystal microbalance(EQCM). The redox reactions of viologen were highly reversible and the EQCM has been employed to monitor the electrochemically induced adsorption of SAMs during the redox reactions.

• Journal of Korean Society for Quality Management
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• v.21 no.2
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• pp.242-253
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• 1993

The interpretation of the reaction mechanism is significant to produce the high quality welds and understand the welding processes. This investigation is important for the design of welding consumables and the selection of welding process parameters to develop the high quality welds. The objective of this study is to investigate the effect of electrochemical reactions on the transfer of alloy elements between slag and weld metal during submerged arc welding During submerged arc welding weld metal composition is shown to be controlled by two reaction mechanisms in four reaction zones. The responsible reaction mechanisms are thermochemical and electrochemical reactions. The possible reaction sites are the melted electrode tip, the detached droplet, the hot weld pool immediately below the moving electrode, and the cooling and solidifying weld pool behind the moving electrode. The possible reactions in submerged arc welding at different zones of the process is schematically shown in Figure 1.

• 한국전기화학회:학술대회논문집
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• 1998.10a
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• pp.35-35
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• 1998

• Journal of Electrochemical Science and Technology
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• v.11 no.3
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• pp.220-237
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• 2020

Modern electrochemical energy devices involve generation and reduction of fuel gases through electrochemical reactions of water splitting, alcohol oxidation, oxygen reduction, etc. Initially, these processes were executed in the presence of noble metal-based catalyst that showed low overpotential and high current density. However, its high cost, unavailability, corrosion and related toxicity limited its application. The search for alternative with high stability, durability, and efficiency led scientists towards carbon nanoparticles supported catalysts which has high surface area, good electrical conductivity, tunable morphology, low cost, ease of synthesis and stability. Carbon nanoparticles are classified into two groups based on morphology, one and zero dimensional particles. Carbon nanoparticles at zero dimension, denoted as carbon dots, are less used carbon support compared to other forms. However, recently carbon dots with improved electronic properties have become popular as catalyst as well as catalyst support. This review focused on the recent advances in electrocatalytic activities of carbon dots. The mechanisms of common electrocatalytic reactions and the role of the catalysts are also discussed. The review also proposed future developments and other research directions to overcome current limitations.