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명노승,전종호,Krishnan Rajeshwar 建國大學校 自然科學硏究所 1997 建國自然科學硏究誌 Vol.8 No.-
This short Note shows that a simple and general relationship exists for the dilution of molal solutions analogous to molarity and normality; X x W = X' x W' wherein X and W are the weight fraction of solute and mass of solution and the primed quantities refer to those after dilution. Two specific examples are given to show the utilities of the expression.
Compositional Analyses of Electrodeposited II-VI Compound Semiconductor Thin Films
이명진,최홍진,전종호,명노승 건국대학교 자연과학연구소 1998 建國自然科學硏究誌 Vol.9 No.2
Cd+Se 혼합물의 열화학적 성질을 DSC를 이용하여 조사하였다. Cd과 Se분말을 이용하여 분석한 결과 Cd이 녹기 전 까진 CdSe의 형성이 관측되지 않았지만, Cd의 녹는 점 이상에서는 온도와 반응시간에 따라 상당한 양의 CdSe가 만들어지는 것을 알 수 있었다. 이상의 방법을 토대로 전기 화학적으로 합성한 CdSe박막의 조성을 분석하였다. 일정 전압에서 합성한 CdSe 박막을 DSC로 분석한 결과 Cd,Se 그리고 CdSe의 양을 각각 분석할 수 있었다. The thermochemistry of the condensed-phase Cd+Se=CdSe system was studied by differential scanning calorimetry(DSC). Formation of CdSe was not initiated until fusion of Cd reactant. However, increase of temperature or reaction time resulted in the formation of CdSe although there was no clear exothemic peak. Based on the thermochemistry of Cd+Se system, compositional analysis of electrodeposited CdSe thin films by the DSC was described. Potentiostatic deposition of CdSe thin films contained free Cd, free Se and CdSe depending on the deposition potential. Interesting features of Se thermochemistry were also described.
Lee, Wooju,Myung, Noseung,Rajeshwar, Krishnan,Lee, Chi-Woo The Korean Electrochemical Society 2013 Journal of electrochemical science and technology Vol.4 No.4
This study describes the electrodeposition of $Cu_2Se$ thin films with a two-step approach that is based on the initial modification of polycrystalline Au electrode with a selenium overlayer followed by a cathodic stripping of the layer as $Se^{2-}$ in a 1 M lactic acid electrolyte containing $Cu^{2+}$ ions. For this two-step approach to be effective, the $Cu^{2+}$ reduction potential should be shifted to more negative potentials passed potentials for the reduction of Se to $Se^{2-}$. This was accomplished by the complexation of $Cu^{2+}$ ions with lactic acid. The resultant $Cu_2Se$ films were characterized by linear sweep voltammetry combined with electrochemical quartz crystal microgravimetry, UV-vis absorption spectrometry and Raman spectroscopy. Photoelectrochemical experiments revealed that $Cu_2Se$ synthesized thus, behaved as a p-type semiconductor.
수은 막전극을 이용한 수용액 중 과염소산이온의 전기화학적 환원
명노승,김은영,지형우,금나래,이인숙,팽기정,Myung, Noseung,Kim, Eun Young,Jee, Hyung-Woo,Keum, Narae,Rhee, Insook,Paeng, Ki-Jung 한국전기화학회 2016 한국전기화학회지 Vol.19 No.3
A method for electrochemical degradation of the perchlorate anion ($ClO_4{^-}$) using mercury film electrode has been studied. Electrochemical method has relatively simple pre-treatment. However, electrochemical method should avoid interference from hydrogen evolution at the applied potential to degradation of perchlorate ion, and thus applied electrode should have large hydrogen overvoltage which suppressed the hydrogen evolution at the working reduction potential to prevent hydrogen evolution. In this study, we used mercury film electrode as a working electrode which has a large overvoltage. Ag / AgCl (sat. NaCl) was used as a reference electrode, and platinum was used as a counter electrode. Mercury film electrode was made by cyclic voltammetry (CV) method. The deposition time was decided as 10 minute, and the stability of the mercury electrode in perchlorate solution was confirmed by CV. The reduction potential of perchlorate was checked by using CV method, and decomposition of perchlorate was performed by using chronoamperometric (CA) method. Also, ion chromatography (IC) was used to confirm the degradation rates of perchlorate. 과염소산이온의 전기화학적 분해에 관한 연구가 진행되었다. 전기화학적 방법은 비교적 단순한 전처리 방법으로 가능하다. 하지만 전기화학적 방법은 과염소산이온이 분해되는 전압을 가해주었을 때 수소발생으로 인한 방해가 발생하기 때문에 사용하는 전극의 수소 과전압이 큰 것을 사용하여 수소발생을 줄이는 것이 요구되어 왔다. 본 연구에서는 수소 과전압이 큰 수은박막전극을 작업 전극으로 사용하였다. Ag / AgCl (sat. NaCl) 전극을 기준전극으로 사용하였으며 Pt를 상대전극으로 사용하였다. 수은박막전극은 순환 전압-전류법(Cyclic voltammetry, CV)으로 제작하였는데 과염소산 용액에서의 CV를 고려하여 수은박막전극의 안정성을 위해 10분 동안 전착시켰다. 과염소산이온의 환원전위는 CV 방법에 의해 설정되었고, 분해실험은 시간대 전류법 (Chronoamperometry, CA)로 시행하였다. 과염소산이온의 분해율 확인을 위해 이온 크로마토그래피(Ion chromatography, IC)를 사용하였다.
Jee, Hyung-Woo,Paeng, Ki-Jung,Myung, Noseung,Rajeshwar, Krishnan The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.13
<P>The mechanism of electrodeposition of cobalt selenide (CoSe) thin films was investigated by the combined application of linear sweep voltammetry (LSV) and electrochemical quartz crystal microgravimetry (EQCM) on Pt-coated quartz electrodes. Cobalt selenide films were electrodeposited on the Pt surface from 0.1 M Na2SO4 electrolyte solution containing 5 mM SeO2 and 5 mM Co(CH3COO)(2) by linear sweep voltammetry. Four cathodic waves were observed during the linear scans and the reactions corresponding to these waves were investigated with LSV and EQCM. Combined stripping voltammetry and EQCM showed that CoSe was electrodeposited via two routes: (1) Underpotential deposition of Se followed by deposition of cobalt as CoSe; and (2) Reaction of Co(II) with electrogenerated Se(-II) to result in CoSe. Compositional analyses revealed that the electrodeposited films contained CoSe and free Se, depending on the deposition potential. However, no cobalt was found in these films because of chemical (galvanic) instability of the cobalt film in the deposition bath. (c) The Author(s) 2017. Published by ECS. All rights reserved.</P>
Jee, Hyung-Woo,Paeng, Ki-Jung,Myung, Noseung,Rajeshwar, Krishnan The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.9
<P>In this study, the composition of electrosynthesized cobalt selenide thin films was analyzed by electrochemical quartz crystal microgravimetry (EQCM) in a continuous flow mode. First, cobalt selenide films were electrodeposited on a Pt-EQCM electrode using a 0.1 M Na2SO4 electrolyte solution containing Co and Se precursor species at different potentials. A combination of sequential stripping and EQCM frequency monitoring protocol enabled mapping of the free Co, free Se, and CoSe content of the electrodeposited films. It was found that the composition of cobalt selenide film was very sensitive to the electrodeposition potential. The targeted CoSe content was maximum at -0.7 V and the free Co content was minimum at this potential. On the other hand, the free Se content decreased from similar to 45% at -0.6 V to nearly 0% at -0.9 V. The film composition as established by the continuous flow analysis mode stood in stark contrast with the static (batch) mode where no free Co was observed in the films. Factors in these compositional differences as well as in the EQCM electrode geometry (face-down vs. face-up) are finally discussed. (C) The Author(s) 2018. Published by ECS.</P>
Jee, Hyung-Woo,Paeng, Ki-Jung,Son, Yongkeun,Jang, Yunhyeok,Rho, Kongshik,Myung, Noseung The Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.5
<P>Cobalt telluride (CoTe) thin films were electrodeposited for the first time using alkaline solutions containing nitrilotriacetic acid (NTA), CoCl<SUB>2</SUB>, and K<SUB>2</SUB>TeO<SUB>3</SUB>. NTA was employed in order to shift the reduction potential of cobalt in the negative direction and to stabilize Co<SUP>2+</SUP> ions in alkaline electrolytes via the formation of Co-NTA complexes. The electrodeposition mechanism was investigated by linear sweep voltammetry (LSV) combined with electrochemical quartz crystal microgravimetry (EQCM). The formation of CoTe is proposed to occur through the reaction of Co<SUP>2+</SUP> with HTe<SUP>−</SUP>, which is generated by the reduction of TeO<SUB>3</SUB><SUP>2−</SUP> via a 6-electron reduction pathway. A concurrent pathway consists of the stepwise reduction of TeO<SUB>3</SUB><SUP>2−</SUP> to Te by a 4-electron process, followed by the 2-electron process reduction of Te to HTe<SUP>−</SUP>. The electrodeposited CoTe films were characterized by a variety of physical methods including scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, and X-ray photoelectron spectroscopy. An optical energy bandgap of ∼1.86 eV was obtained by diffuse reflectance spectroscopy.</P>