• Title, Summary, Keyword: 산화환원 메커니즘

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Electrochemical Studies on Some Substituted Thiadiazoles (몇 가지 치환 Thiadiazole에 대한 전기화학적 연구)

  • El Maghraby, A. A.;Abou-Elenien, G. M.;Abdel-Reheem, N. A.;Abdel-Tawab, H. R.
    • Journal of the Korean Chemical Society
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    • v.50 no.4
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    • pp.307-314
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    • 2006
  • The redox characteristics of 2-ketohydrazono-3-phenyl-5-substituted-2,3-dihydro-1,3,4-thiadiazoles and its derivatives (1a-h) has been investigated in nonaqueous solvents such as 1,2-dichloroethane (DCE), dichloromethane (DCM), acetonitrile (AN), tetrahydrofuran (THF), and dimethylsulfoxide (DMSO) containing 0.1 mol.dm-3 tetra n-butylammonium perchlorate (TBAP) as supporting electrolyte at platinum ectrode. Through controlled potential electrolysis, the oxidation and reduction products of the investigated compounds can be separated and indentified. The redox mechanism is suggested and proved. It was found that all the investigated compounds are oxidized in two irreversible one-electron processes following the well known pattern of EC-mechanism. On the other hand, these compounds are reduced in a single two electron or in a successive two one electron processes following the well known pattern of EEC-mechanism according to the nature of the substituent

Pyro-Electrochemical Reduction of a Mixture of Rare Earth Oxides and NiO in LiCl molten Salt (LiCl 용융염에서 NiO를 혼합한 희토류 산화물의 파이로 전해환원 특성)

  • Lee, Min-Woo;Jeong, Sang Mun
    • Korean Chemical Engineering Research
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    • v.55 no.3
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    • pp.379-384
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    • 2017
  • An electrochemical reduction of a mixture of NiO and rare earth oxides has been conducted to increase the reduction degree of rare earth oxides. Cyclic voltammetry (CV) measurement was carried out to determine the electrochemical reduction behavior of the mixed oxide in molten LiCl medium. Constant voltage electrolysis was performed with various supplied charges to understand the mechanism of electrochemical reduction of the mixed oxide as a working electrode. After completion of the electrochemical reduction, crystal structure of the reaction intermediates was characterized by using an X-ray diffraction method. The results clearly demonstrate that the rare earth oxide was converted to RE-Ni intermetallics via co-reduction with NiO.

Resazurin Redox Reaction Mechanism Using Silver Nanoparticles Synthesized with Monosaccharides and Disaccharides (단당류와 이당류를 환원제로 합성한 은 나노입자의 Resazurin 산화환원반응 메커니즘)

  • Park, Young Joo;Chang, Ji Woong
    • Applied Chemistry for Engineering
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    • v.31 no.3
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    • pp.299-304
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    • 2020
  • Nanoparticles play an important role as a catalyst in many chemical syntheses. Colloidal nanoparticles were usually synthesized with reducing, capping, and shape directing agents which induce surface poisoning of catalysts. A new green synthesis for silver nanoparticles was developed by utilizing less additives which could be a hazardous waste. A crystallization technique was employed to reduce the amount of reducing and capping agents during synthesis resulting in less surface poisoning of the nanoparticle. The synthesized Ag nanoparticles using monosaccharides and disaccharides as reducing agents could be used as a catalyst for the redox reaction of resazurin and the mechanism of the reaction using Ag nanoparticles was studied.

Electron Energy Loss Spectroscopy (EELS) Application to Mineral Formation (전자에너지 손실분광 분석법을 이용한 광물에서의 정량적 철 산화수 측정과 분석)

  • Yang, Kiho;Kim, Jinwook
    • Journal of the Mineralogical Society of Korea
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    • v.29 no.2
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    • pp.73-78
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    • 2016
  • The oxidation states of structural Fe in clay minerals often reflect the paleo-redox conditions of the depositional environments. It is inevitable to utilize the high resolution of transmission electron microscopy (TEM) to investigate the mechanism of mineral transformation at nano-scale. The applications of TEM- electron energy loss spectroscopy (EELS) for quantification of $Fe(III)/{\Sigma}Fe$ from the K-nontronite formation associated with structural Fe(III) reduction in nontronite under deep subseafloor environment were demonstrated. In particular, quantification of the changes in Fe-oxidation state at nanoscale is essential to understand the mechanisms of minerals formation. The procedure of EELS acquisition, quantitative determination of Fe-oxidation states, and advantages of EELS techniques were discussed.

Characteristics of the TCE removal in FeO/Fe(II) System (FeO/Fe(II) 시스템에서 TCE의 제거 특성)

  • Sung, Dong Jun;Lee, Yun Mo;Choi, Won Ho;Park, Joo yang
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.1B
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    • pp.149-152
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    • 2008
  • The reaction between iron oxide and ferrous iron is known to be the adsorption of ferrous iron onto the oxide surfaces that produces Fe(II)-Fe(III) (hydr)oxides and ferrous oxide oxidized to ferric ion which is the reducing agent of the target compounds. In our investigations on DS/S using ferrous modified steel slag, the results did not follow the trends. FeO and Fe(II), the major component of steel slag, were used to investigate the degradation of TCE. Degradation did not take place for the first and suddenly degraded after awhile. Degradation of TCE in this system was unexpected because Fe(II)-Fe(III) (hydr)oxides could not be produced in absence of ferric oxide. In this study, the characteristics of FeO/Fe(II) system as a reducing agent were observed through the degradation of TCE, measuring byproducts of TCE and the concentration of Fe(II) and Fe(III). Adsorption of ferrous ion on FeO was observed and the generation of byproducts of TCE showed the degradation of TCE by reduction in the system is obvious. However it did not correspond with the typical reducing mechanisms. Future research on this system needs to be continued to find out whether new species are generated or any unknown mineral oxides are produced in the system that acted in the degradation of TCE.

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Carbon nanofiber and metal oxide composites for photovoltaic cells

  • O, Dong-Hyeon;Gu, Bon-Yul;Bae, Ju-Won;An, Hyo-Jin
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.412-412
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    • 2016
  • 염료감응 태양전지(dye-sensitized solar cells, DSSCs)는 식물의 광합성원리와 매우 유사한 작동원리를 갖고 있는 전지이며, 간단한 구조, 저렴한 제조단가, 친환경성 등의 등의 장점으로 인하여 많은 관심을 모으고 있다. 이러한 염료감응 태양전지는 빛을 받아들인 염료분자가 전자-홀 쌍을 생성하며 전자는 반도체 산화물을 통해 이동되고 전해질의 산화환원 과정을 통해 염료 분자가 다시 환원되는 순환메커니즘을 따르고 있다. 일반적으로 염료감응 태양전지는 밴드 갭 에너지가 큰 반도체 산화물을 포함하는 작업전극, 산화환원 반응을 통해 전자를 염료로 보내는 전해질, 환원 촉매역할을 하는 상대전극으로 구성되어 있다. 특히, 상대전극으로는 우수한 촉매특성과 높은 전도성을 갖는 백금이 가장 많이 이용되고 있지만 가격이 비싸고 요오드에 취약하기 때문에 상용화에 큰 장애물이다. 따라서, 백금을 대체하기 위해 저가의 탄소나 고분자에 대한 연구가 활발히 진행되고 있고, 그 중 탄소나노섬유(carbon nanofiber, CNFs)는 높은 표면적과 뛰어난 화학적 안정성으로 촉매효율을 증대시킬 수 있어 촉매물질로서 관심이 높아지고 있다. 본 연구에서는 상대전극에 탄소나노섬유기반 복합체를 합성하였고, 성공적으로 저가격 및 고성능의 염료감응 태양전지를 제작하였다. 이때, 지지체인 탄소나노섬유는 전기방사법을 통해 합성하였으며, 수열합성법을 이용하여 금속산화물을 담지하였다. 이렇게 제작된 탄소나노섬유-Fe2O3 복합체는 scanning electron microscopy, transmission electron microscopy, X-ray diffraction, 그리고 X-ray photoelectron spectroscopy 통해 구조적, 화학적 특성을 평가하였으며 전기화학적 특성 및 광전변환 효율을 분석하기 위해 cyclic voltammetry, electrochemical impedance spectroscopy, 그리고 solar simulator를 사용하였다. 본 학회에서 위와 관련된 더 자세한 사항에 대해 논의할 것이다.

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Anodic Dissolution of Electrodeposited Iron Group Elements in Phthalate Buffer Solution (Phthalate 완충용액에서 전해 석출한 철족 원소의 산화 용해 반응)

  • Chon, Jung-Kyoon;Kim, Youn-Kyoo
    • Journal of the Korean Chemical Society
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    • v.51 no.1
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    • pp.14-20
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    • 2007
  • The anodic dissolution of electrodeposited iron group elements (Fe, Co, Ni) were studied in phthalate buffer solution. The pH dependence of the corrosion potential, the corrosion current and Tafel slope was measured for each element. Based on the electrochemical parameters including Tafel slopes, we proposed the redox mechanism of the corrosion and the passivation. The adsorption of various phthalate species on the electrodeposited iron group elements seemed to be affected the corrosion mechanisms.

Removal of SO2 over Binary Nb/Fe Mixed Oxide Catalysts (이성분계 Nb/Fe 혼합산화물 촉매에 의한 아황산가스의 제거)

  • Chung, Jong Kook;Lee, Seok Hee;Park, Dae Won;Woo, Hee Chul
    • Clean Technology
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    • v.12 no.2
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    • pp.87-94
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    • 2006
  • The reduction of $SO_2$ to elemental sulfur by CO over a series of iron niobate with nominal Nb/Fe atomic ratios of 1/0, 10/1, 5/1, 1/1, 1/5, 1/10 and 0/1 was studied with a flow fixed-bed reactor. Strong synergistic phenomena in catalytic activity and selectivity were observed for the iron niobate catalysts, and the best catalytic performance was observed for the catalyst with Fe/Nb atomic ratio of 1/1. The active phase of the activated iron niobate catalysts was identified to be $FeS_2$ using XRD and XPS. Selective reduction of $SO_2$ by CO was followed by the COS intermediate mechanism.

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Quantitative Determination of Fe-oxidation State by Electron Energy Loss Spectroscopy (EELS) (전자에너지 손실분광 분석법을 이용한 정량적 철산화수 측정)

  • Yang, Ki-Ho;Kim, Jin-Wook
    • Economic and Environmental Geology
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    • v.45 no.2
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    • pp.189-194
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    • 2012
  • The consequences of microbe-mineral interaction often resulted in the chemical, structural modification, or both in the biologically induced mineral. It is inevitable to utilize the high powered resolution of electron microscopy to investigate the mechanism of biogenic mineral transformation at nano-scale. The applications of transmission electron microscopy (TEM) capable of electron energy loss spectroscopy (EELS) to the study of microbe-mineral interaction were demonstrated for two examples: 1) biogenic illite formation associated with structural Fe(III) reduction in nontronite by Fereducing bacteria; 2) siderite phase formation induced by microbial Fe(III) reduction in magnetite. In particular, quantification of the changes in Fe-oxidation state at nanoscale is essential to understand the dynamic modification of minerals resulted from microbial Fe reduction. The procedure of EELS acquisition and advantages of EELS techniques were discussed.

Corrosion and Passivation of Copper in Artificial Sea Water (인공해수에서 구리의 부식과 부동화 반응)

  • Chon, Jung-Kyoon;Kim, Youn-Kyoo
    • Journal of the Korean Chemical Society
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    • v.51 no.4
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    • pp.305-311
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    • 2007
  • Based on the cyclic voltammograms, potentiodynamic polarizations, transient and steady state Tafel plots and electrochemical impedence spectroscopy, we proposed the copper redox mechanism of the corrosion and passivation in artificial sea water. The copper redox mechanism showed the dependence of the concentration of oxygen in artificial sea water and electrode potentials.