• Journal of Environmental Science International
• /
• v.19 no.8
• /
• pp.951-960
• /
• 2010

Sediment works as a resource for electric cells. This paper was designed in order to verify how sediment cells work with anodic material such as metal and carbon fiber. As known quite well, sediment under sea, rivers or streams provides a furbished environment for generating electrons via some electron transfer mechanism within specific microbial population or corrosive oxidation on the metal surfaces in the presence of oxygen or water molecules. We experimented with one type of sediment cell using different anodic material so as to attain prolonged, maximum electric power. Iron, Zinc, aluminum, copper, zinc/copper, and graphite felt were tested for anodes. Also, combined type of anodes-metal embedded in the graphite fiber matrix-was experimented for better performances. The results show that the combined type of anodes exhibited sustainable electricity production for ca. 600 h with max. $0.57\;W/m^2$ Al/Graphite. Meanwhile, graphite-only electrodes produced max. $0.11\;W/m^2$ along with quite stationary electric output, and for a zinc electrode, in which the electricity generated was not stable with time, therefore resulting in relatively sharp drop in that after 100 h or so, the maximum power density was $0.64\;W/m^2$. It was observed that the corrosive reaction rates in the metal electrodes might be varied, so that strength and stability in the electric performances(voltage and current density) could be affected by them. In addition to that, COD(chemical oxygen demand) of the sediment of the cell system was reduced by 17.5~36.7% in 600 h, which implied that the organic matter in the sediment would be partially converted into non-COD substances, that is, would suggest a way for decontamination of the aged, anaerobic sediment as well. The pH reduction for all electrodes could be a sign of organic acid production due to complicated chemical changes in the sediment.

• Applied Chemistry for Engineering
• /
• v.9 no.7
• /
• pp.1030-1035
• /
• 1998

The porous alumina membrane was prepared from aluminum metal(99.8%) by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. To prevent the chemical dissolution of alumina membrane, $Al_2(SO_4)_3$, $AlPO_4$ and $Al(NO_3)_3$ which could be considered to supply $Al^{3+}$ ions were added to electrolyte solution at a reaction temperature of $20^{\circ}C$ and cumulative charge of $150C/cm^2$. Effects of these additives on the formation of porous alumina membrane were evaluated under various electrolyte concentration(5~20 wt%) and current densities($10{\sim}50mA/cm^2$). The membrane surfaces which were prepared in electrolyte solution with all the additives except $Al_2(SO_4)_3$ were damaged. However, when $Al_2(SO_4)_3$ was added to the $H_2SO_4$ solution, an uniform surface of porous alumina was obtained. Also, it was shown that the pore size of membrane was nearly independent on the quantity of $Al_2(SO_4)_3$ added at same electrolyte concentration and current density.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.3 no.4
• /
• pp.269-278
• /
• 2005

In order to produce only a pH-controlled solution without discharging any unwanted solution, this work has developed a continuous electrolytic system with a pH-adjustment reservoir being placed before an ion exchange membrane-equipped electrolyzer, where as a target solution was fed into the pH-adjustment reservoir, some portion of the solution in the pH-adjustment reservoir was circulated through the cathodic or anodic chamber of the electrolyzer depending on the type of the ion exchange membrane used, and some other portion of the solution in the pH-adjustment reservoir was discharged from the electrolytic system through the other counter chamber with its pH being controlled. The internal circulation of the pH-adjustment reservoir solution through the anodic chamber in the case of using a cation exchange membrane and that through the cathodic chamber in the case of using an anion exchange membrane could make the solution discharged from the other counter chamber effectively acidic and basic, respectively. The phenomena of the pH being controlled in the system could be explained by the electro-migration of the ion species in the solution through the ion exchange membrane under a cell potential difference between anode and cathode and its consequently-occurring non-charge equilibriums and electrolytic water- split reactions in the anodic and cathodic chambers.

• Journal of the Korean Chemical Society
• /
• v.18 no.4
• /
• pp.244-250
• /
• 1974

The mechanisms of the electrode reaction of chlorate ion were investigated, using Pt-electrode, by means of the technique of galvanostatic double pulses. For double current pulses (a cathodic pulse followed by an anodic pulse), the mechanism of the electrode reaction of chlorate ion over a current density range from 20 ma/cm2 to 25 ma/cm2 was suggested as the following: $CIO_3^-\;{\longrightarrow^{I}_{n_{1c}}\;CIO_2^-\;{\longrightarrow^{II}_{n_{2a}}\;CIO^-\;{\longrightarrow^{I'}_{n_{1a}}\;CIO_2^-\;{\longrightarrow^{II'}_{n_{2a}}\;CIO_4^-$ For a higher current density from 40 ma/cm2, it was suggested as the following: $CIO_3^-\;{\longrightarrow^{III}_{n_c}}\;CIO^-\;{\longrightarrow^{I'}_{n_{1a}}\;CIO_2^-\;{\longrightarrow^{II'}_{n_{2a}}\;CIO_4^-$ or $CIO_3^-\;{\longrightarrow_{n_c}}\;CIO^-\;{\longrightarrow_{n_a}}\;CIO_4^-$

• Transactions of the Korean hydrogen and new energy society
• /
• v.23 no.5
• /
• pp.503-512
• /
• 2012

There is a new power generation system such as direct coal fuel cell (DCFC) with a solid oxide electrolyte operated at relatively high temperature. In the system, it is of great importance to feed coal continuously into anodic electrode surface for its better contact, otherwise it would reduce electrochemical conversion of coal. For that purpose, it is required to improve the electrochemical conversion efficiency by using either rigorous mixing condition such as fluidized bed condition or just by recirculating coal particle itself successively into the reaction zone of the system. In this preliminary study, we followed the second approach to investigate how significantly particle recycle would affect the coal conversion efficiency. As a first phase, coal conversion was analyzed and evaluated from the thermochemical reaction of carbon with air under particle recirculating condition. The coal conversion efficiency was obtained from raw data measured by two different techniques. Effects of temperature and fuel properties on the coal conversion are specifically examined from the thermochemical reaction.

• Journal of the Korean Chemical Society
• /
• v.39 no.3
• /
• pp.198-203
• /
• 1995

The Mo(V) $di-\mu-oxo$ type $(Mo_2O_4(H_2O)_2L)$ complexes $(L:\;C_3H_7CH(SCH_2COOH)_2,\;C_6H_5CH(SCH_2COOH)_2,\;CH_3OC_6H_4CH(SCH_2COOH)_2,\;C_5H_{10}C(SCH_2COOH)_2,\;C_3H_7C(CH_3)(SCH_2COOH)_2,\;C_3H_7CH(SCH_2CH_2COOH)_2,\;C_6H_5CH(SCH_2CH_2COOH)_2)$ have been prepared by the reaction of $[Mo_2O_4(H_2O)_6]^{2+}$ with a series of dithiodicarboxy ligands. These complexes are completed by two terminal oxygens arranged trans to one another and each ligand forms a chelate type between two molybdenum. In $Mo_2O_4(H_2O)_2L$, two $H_2O$ coordinated at trans site of terminal oxygens. The prepared complexes have been characterized by elemental analysis, infrared spectra, electronic spectra, and nuclear magnetic resonance spectra. In the potential range -0.00 V to -1.00 V at a scan rate of 20 $mVs^{-1}$, a cathodic peak at -0.50∼-0.58 V (vs. SCE) and an anodic peak at -0.40∼-0.43 V (vs. SCE) have been observed in aquous solution. The ratio of the cathodic to anodic current ($I_{pc}/I_{pa}$) is almost 1, we infer that redox is reversible reaction.

• Transactions of the Korean hydrogen and new energy society
• /
• v.26 no.3
• /
• pp.227-233
• /
• 2015

In this study, we evaluate catalytic activity of Pd/C catalyst that is synthesized by modified polyol method. With such formed Pd/C is used as anodic catalyst for direct formic acid fuel cell (DFAFC) and performances of the DFAFC are measured to verify whether the new catalyst is effective for enhancing DFAFC performance and to determine optimal loadings of the Pd/C needed for obtaining best DFAFC performance. Pd particle distribution of the Pd/C catalyst is analyzed by TEM, while its catalytic activity is estimated by using cyclic voltammogram (CV) as measuring formic acid oxidation reaction and active surface area. As a result of that, the Pd/C catalyst synthesized by modified polyol shows better catalytic activity and DFAFC performance with small loading amount of Pd/C. When loading amount of Pd/C is $1.5mgcm^{-2}$, maximum power density of DFAFC adopting the catalyst is $122mWcm^{-2}$.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.99.1-99.1
• /
• 2017

$TiO_2$는 기계적, 화학적 안정성이 높아 가혹한 화학적 환경 또는 고온 운전 조건에서 훌륭한 내구성을 보여주어 산업적으로 일찍이 널리 이용되어 왔다. 예를 들어, 염소발생 (chlorine evolution reaction) 또는 산소발생반응은 (oxygen evolution reaction) 염소 또는 산소 라디칼에 전극이 지속적으로 노출되기에 강한 내부식성을 지닌 전극재가 요구되었고, 그 결과 $TiO_2$를 골조로 한 불용성전극 (dimensionally stable anode)이 개발되어 이용되고 있다. 그러나, $TiO_2$는 절연성이 높은 금속 산화물 재료이기 때문에 넓은 표면적 획득 및 촉매제 사용을 통해 소재의 단점을 극복해야만 한다. 넓은 반응 표면적 획득의 한 방법으로써 전기화학적 양극산화 (electrochemical anodization)를 통한 $TiO_2$ 나노튜브 제조법은 경제적이면서도 구조 제어도 간편한 방법이다. $TiO_2$ 나노튜브는 100nm 전후의 기공 크기를 가짐과 동시에 매우 높은 종횡비를 지니고 있어 넓은 반응 표면적 획득에 특히 유리하다. 그러나, 이 높은 종횡비는 촉매 도입을 어렵게 하는 저해요소가 되기도 한다. 이러한 문제를 해결하기 위하여 다양한 방법들이 연구되었으나 대부분이 번거롭거나 비싼 후단공정을 필요로 한다. 본 연구에서는 $TiO_2$ 나노튜브에 촉매를 도핑하기 위한 간단한 전기화학적 방법으로, 단일공정 양극산화법 (single-step anodization)과 전압충격법 (potential shock), 그리고 저전압충격법 (under potential shock)을 연구하였으며 이에 적용 가능한 촉매제의 종류를 소개한다. 또한, 촉매의 성질에 따른 응용분야와 그 성능평가 결과를 제시한다.

• Journal of the Korean Chemical Society
• /
• v.17 no.5
• /
• pp.378-384
• /
• 1973

To investigate the mechanism of the reaction of electrolytic oxidation of iodide to iodate ions, polarization curves are determined in various kinds of solution using electrodeposited lead peroxide and platinum anodes. It was observed from the polarization curves that the limiting current is exists at concentration 1.5 M of potassium iodide, and these limiting current disappeared as potassium hydroxide was added up to concentration of 0.1 M. while in case of platinum anode, limiting current did not appear in dilute potassium iodide solution. These results are owing to the chemical reaction, $PbO_2+2I^{-}+2H^+{\to}PbO+I_2+H_{2}O$ ocurring at the surface of lead peroxide anode. Also, we studied to obtain the optimum conditions of electrolytic preparation of iodate from iodide solution using a cell without the diaphragm. The results are that; (a) addition of potassium dichromate at the anti-reducing agent is proper in concentration of 0.1 g/l, (b) electrolytic temperature is not so much effective in raising the current efficiency, (c) current efficiency is increased with current density, and (d) electrolysis is the most effective in weak alkaline solutions.

• Korean Journal of Materials Research
• /
• v.15 no.8
• /
• pp.536-542
• /
• 2005

Recently European Council(EU) published the RoHS(restriction of the use of certain hazardous substances in electrical and electronic equipment) which is prohibit the use of Pb, Hg, Cd, $Cr^{+6}$, PBB or PBDE in the electrical and electronic equipments. So EU member States shall ensure that, from 1 July 2006, new electrical and electronic equipment put on the market does not contain 6 hazardous substances. The one of the most important in electronics manufacturing process is soldering. Soldering process use the chemical substances which are applied in fluxing and cleaning processes and it can generate the malfunction of electronics caused by corrosion in the fields conditions. Therefore this study researched on the polarization and Tafel properties of Sn40Pb and Sn3.0Ag0.5Cu(SAC) solder based on the electrochemical theory. We prepared SnPb specimens which was aged in $150^{\circ}C,\;180^{\circ}C$ for 15 minutes ana Sn3.0Ag0.5Cu specimens that was aged in $180^{\circ}C,\;220^{\circ}C$ for 10 minutes. Experimental polarization curves were measured in distilled ionized water and $3.5 wt\%$, 1 mole NaCl electrolyte of $40^{\circ}C$, pH 7.5. Ag/AgCl and graphite were utilized by reference and counter electrode, respectively. To observe the electrochemical reaction, polarization test was conducted from -250 mV to +250 mV. From the polarization curves that were composed of anodic and cathodic curves, we obtained Tafel slop, reversible electrode potential(Ecorr) and exchange current density(Icorr). In these results, corrosion rate for two specimen were compared Sn3.0Ag0.5Cu with SnPb solders