• Journal of Microbiology and Biotechnology
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• v.17 no.1
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• pp.110-115
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• 2007

Electrochemically active bacteria were successfully enriched in an electrochemical cell using a positively poised working electrode. The positively poised working electrode (+0.7 V vs. Ag/AgCl) was used as an electron acceptor for enrichment and growth of electrochemically active bacteria. When activated sludge and synthetic wastewater were fed to the electrochemical cell, a gradual increase in amperometric current was observed. After a period of time in which the amperometric current was stabilized (generally 8 days), linear correlations between the amperometric signals from the electrochemical cell and added BOD (biochemical oxygen demand) concentrations were established. Cyclic voltammetry of the enriched electrode also showed prominent electrochemical activity. When the enriched electrodes were examined with electron microscopy and confocal scanning laser microscopy, a biofilm on the enriched electrode surface and bacterium-like particles were observed. These experimental results indicate that the electrochemical system in this study is a useful tool for the enrichment of an electrochemically active bacterial consortium and could be used as a novel microbial biosensor.

• Journal of Microbiology and Biotechnology
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• v.9 no.2
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• pp.127-131
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• 1999

Anaerobically grown cells of an Fe(III)-reducing bacterium, Shewanella putrefaciens IR-l, were electrochemically active with an apparent reduction potential of about 0.15 V against a saturated calomel electrode in the cyclic voltammetry. The bacterium did not grow fermentatively on lactate, but grew in an anode compartment of a three-electrode electrochemical cell using lactate as an electron donor and the electrode as the electron acceptor. This property was shared by a large number of Fe(III)-reducing bacterial isolates. This is the first observation of a direct electrochemical reaction by an intact bacterial cell, which is believed to be possible due to the electron carrier(s) located at the cell surface involved in the reduction of the natural water insoluble electron acceptor, Fe(III).

• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.30-38
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• 2013

In this study, a catalyst slurry was prepared with a Pt/C catalyst, Nafion ionomer solution as a binder, an ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate), deionized water and ethanol as a solvent for the application to polymer electrolyte fuel cells (PEFCs) at high-temperatures. The effect of the IL in the electrode of each design was investigated by performing a cyclic voltammetry (CV) measurement. Electrodes with different IL distributions inside and on the surface of the catalyst electrode were examined. During the CV test, the electrochemical surface area (ESA) obtained for the Pt/C electrode without ILs gradually decreased owing to three mechanisms: Pt dissolution/redeposition, carbon corrosion, and place exchange. As the IL content increased in the electrode, an ESA decrement was observed because ILs leaked from the Nafion polymer in the electrode. In addition, the CVs under conditions simulating leakage of ILs from the electrode and electrolyte were evaluated. When the ILs leaked from the electrode, minor significant changes in the CV were observed. On the other hand, when the leakage of ILs originated from the electrolyte, the CVs showed different features. It was also observed that the ESA decreased significantly. Thus, leakage of ILs from the polymer electrolyte caused a performance loss for the PEFCs by reducing the ESA. As a result, greater entrapment stability of ILs in the polymer matrix is needed to improve electrode performance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1626-1631
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• 2010

The characteristics of electric current for the voltaic cell are important for electric power applications. In this paper, an electrical equivalent model consist of three resisters and a capacitance for the Cu/NaCl solution/Zn electrochemical cell is proposed. The capacitance which exists in the Zn electrode/electrolytic interface increased according to Zn electrode area, but cannot affect almost in electric current. Complex impedance plot was used to analysis the interface effect for Zn/electrolyte. This result shows that the interface is similar with the electric transmission line. The short current measurements were conducted to investigate the effects of hydrogen peroxide, the watery sulfuric acid and NaCl aqueous solution. As the hydrogen peroxide increased, the electric current increased because the hydrogen gas being converted with the water. Also electric current increased significantly with increase of the hydrogen ion with the watery sulfuric acid and increased with increase of $Na^+$ ion and $Cl^-$ion in the NaCl electrolyte.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.106-114
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• 2005

This article covers the theoretical ac-impedance models for the analysis of oxygen reduction on the porous cathode electrode f3r solid oxide fuel cell (SOFC). Firstly, ac-impedance models were explained on the basis of the mechanism of oxygen reduction, which were classified into the rate-determining steps; (i) adsorption of oxygen atom on the electrode surface, (ii) diffusion of adsorbed oxygen atom along the electrode surface towards the three-phase (electrode/electrolyte/gas) boundaries, (iii) surface diffusion of adsorbed oxygen atom m ixed with the adsorption reaction of oxygen atom on the electrode surface and (iv) diffusion of oxygen vacancy through the electrode coupled with the charge transfer reaction at the electrode/gas interface. In each section for ac-impedance model, the representative impedance plots and the interpretation of important parameters attributed to the oxygen reduction reaction were explained. Finally, we discussed in detail the applications of the proposed theoretical ac-impedance models to the real electrode of SOFC system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.82-92
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• 2022

This study aims to investigate the effect of total electrochemical cell resistance (TECR) on electrochemical impedance (EI) measurements of reinforced concrete (RC) by electrochemical impedance spectroscopy (EIS) using a three-electrode system. A series of experimental study is performed to measure electrochemical behavior of a steel bar embedded in a concrete cube specimen, with a side length of 200 mm, in various experimental conditions. Main variables include concrete dry conditions, coupling resistance between sensing electrodes and concrete surface, and area of the counter electrode. It is demonstrated that EI values remains stable when the compliant voltage of a measuring device is sufficiently great compared to the potential drop caused by TECR of concrete specimens. It is confirmed that the effect of the coupling resistance of TECR is far more influential than other two factors (concrete dry conditions and area of the counter electrode). The results in this study can be used as a fundamental basis for development of a surface-mount sensor for corrosion monitoring of reinforced concrete structures exposed to wet-and-dry cycles under marine environment.

• Journal of the Korean Electrochemical Society
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• v.10 no.2
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• pp.73-81
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• 2007

This review article considered the electrochemical reduction of uranyl ions on a Pt surface. Specifically, we focussed on the improvement in its reduction current efficiency. First, this article briefly explained the fundamentals of the reduction of uranyl ($UO_2^{2+}$) ions on a Pt surface. Namely, they involved the electrochemical behaviour of uranium species, and electrochemical cell configurations for the reduction of $UO_2^{2+}$ ions. In addition, the effects of adsorbed hydrogen atoms were investigated on the reduction of $UO_2^{2+}$ ions. Finally, this article presented the methods for improving current efficiency of the reduction of $UO_2^{2+}$ ions on a Pt surface. Three different kinds of methods are introduced, which include electrochemical surface treatments of Pt electrode involving hydrogenation and anodisation, the use of catalyst poisons, and formation of thin mercury film on a Pt electrode. Moreover, this article provided some clues about how hydrogenation and catalyst poisons work on the reduction of $UO_2^{2+}$ ions.

• Journal of Electrochemical Science and Technology
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• v.14 no.3
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• pp.262-271
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• 2023

For electrode stability and the electrochemical performance of the Li-ion cell, it is essential that the active ingredients and unique additives in the polymer binder be well dispersed with the solvent-based slurry. The efficient procedure used to create the slurry affects the rheological characteristics of the electrode slurry. When successively adding different steps of Nmethyl-2-pyrrolidone (NMP) solvent to the cathode composition, it is evenly disseminated. The electrochemical performance of the Li-ion cells and the electrodes made with slurry formed by single step and multiple steps of addition of NMP solvent are examined. To preform rheological properties of cathode electrode slurry on Ni-rich Lithium Nickel-Cobalt-Aluminum Oxide (LiNi_0.80Co_0.15Al_0.05) (NCA). Also, we investigate different step addition of electrode formation and mechanical strength characterization like peel strength. According to the EIS study, a multi-step electrode slurry has lower internal resistance than a single-step electrode slurry, which results in better electrical characteristics and efficiency. Further, microstructure of electrodes is obtained electrochemical performance in the 18650 cylindrical cells with targeted capacity of 1.5 Ah. The slurry of electrodes prepared by single step and multiple steps of addition of NMP solvent and its effect on the fabrication of 1.5 Ah cells. A three-step solvent addition on slurry has been found to be a lower internal resistance than a single-step electrode slurry as confirmed by the EIS analysis, yielding improved electrical properties and efficiency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.973-978
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• 2004

This work describes the effect of conducting materials on the electrochemical performances of electric double layer capacitor. Three kinds of Carbon black, such as Acethylene Black, Super P Black, Ketjen black supplied by Denki Kagaku Kogyo, MMM Carbon, Ketjen Black International Co. respectively, was added in carbon-Polytetrafluoroethylene (PTFE) electrode, which composition is activated carbon : carbon black : PTFE = 80 : 15 : 5 wt.%, and were compared with their electrochemical properties. The electrode with Ketjen Black has showed the lowest resistance than other carbon black, and also exhibited the better rate capability between 0.5 mA/cm$^2$ ∼ 100 mA/cm$^2$ current density in unit cell capacitor. On the other hand, as increasing the composition of Ketjen Black, the specific resistances of electrodes were decreased and Ketjen Black content higher than 15 wt% increased. The best rate capability was obtained at the electrode with 15 wt.% of Ketjen Black in unit cell capacitor. This behaviors would be correlated with the dense structure of electrode.

• Journal of Electrochemical Science and Technology
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• v.3 no.2
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• pp.72-79
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• 2012

$Li_2MnSiO_4$ was synthesized using the solid-state method under an Ar atmosphere at three different calcination temperatures (900, 950, and $1000^{\circ}C$). The optimization of the carbon coating was also carried out using various molar concentrations of adipic acid as the carbon source. The XRD pattern confirmed that the resulting $Li_2MnSiO_4$ particles exhibited an orthorhombic structure with a $Pmn2_1$ space group. Cyclic voltammetry was utilized to investigate the capacitive behavior of $Li_2MnSiO_4$ along with activated carbon (AC) in a hybrid supercapacitor with a two-electrode cell configuration. The $Li_2MnSiO_4$/AC cell exhibited a high discharge capacitance and energy density of $43.2Fg^{-1}$ and $54Whkg^{-1}$, respectively, at $1.0mAcm^{-2}$. The $Li_2MnSiO_4$/AC hybrid supercapacitor exhibited an excellent cycling stability over 1000 measured cycles with coulombic efficiency over > 99 %. Electrochemical impedance spectroscopy was conducted to corroborate the results that were obtained and described.