• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.522-527
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• 2013

In this paper, We studied the change of surface and variation of elements on both electrodes of hydrogen generator of alkaline electrolysis in use of FE-SEM and SIMS. We used the stainless steel 316(600 ${\mu}m$) as electrode in condition of 25%KOH, $60^{\circ}C$ Temperature. The results show that the intensity of elements (C, Si, P, S, Ti, Cr, Mn, Fe, Ni, Mo) of Positive Electrode are decreased as much as about $10^1{\sim}10^3 $than the original electrode. Thickness of Positive Electrode is decreased about 40 ${\mu}m$ after chemical reaction. The negative electrode, however, shows a slight variation in the intensity of elements (C, Si, P, Fe, Ni, Mn, Mo) but Change of thickness and surface' shape of electrode show nothing after chemical reaction. The change in thickness and variation of Stainless Steel 316 cause the lifetime of electrode to be shorted. We also observed hydrogen, oxygen, potassium in both electrodes. Especially, The potassium is increased in proportional with depth of positive electrode. this means the concentration of alkali solutions is changed. and so we have to supply alkaline solution to generator in order to produce same quantity of hydrogen gas continuously. we hope that this study gives a foundation to develop the electrode for hydrogen generator of alkaline electrolysis.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.161-167
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• 2018

In this study, transition metal coated carbon nanofibers (CNFs) were synthesized and applied as anode materials of Li secondary batteries. CNFs/Ni foam was immersed into 0.01 M transition metal solutions after growing CNFs on Ni foam via chemical vapor deposition (CVD) method. Transition metal coated CNFs/Ni foam was dried in an oven at $80^{\circ}C$. Morphologies, compositions, and crystal quality of CNFs-transition metal composites were characterized by scanning electron microscopy (SEM), Raman spectroscopy (Raman), and X-ray photoelectron spectroscopy (XPS), respectively. Electrochemical characteristics of CNFs-transition metal composites as anodes of Li secondary batteries were investigated using a three-electrode cell. Transition metal/CNFs/Ni foam was directly employed as a working electrode without any binder. Lithium foil was used as both counter and reference electrodes while 1 M $LiClO_4$ was employed as the electrolyte after it was dissolved in a mixture of propylene carbonate:ethylene carbonate (PC:EC) at 1:1 volume ratio. Galvanostatic charge/discharge cycling and cyclic voltammetry measurements were taken at room temperature using a battery tester. In particular, the capacity of the synthesized CNFs-Fe was improved compared to that of CNFs. After 30 cycles, the capacity of CNFs-Fe was increased by 78%. Among four transition metals of Fe, Cu, Co and Ni coated on carbon nanofibers, the retention rate of CNFs-Fe was the highest at 41%. The initial capacity of CNFs-Fe with 670 mAh/g was reduced to 275 mAh/g after 30 cycles.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.3
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• pp.137-141
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• 1997

The effects of Ag addition to Zr-based hydrogen storage alloys ($Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.4}$, $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.3}Cr_{0.1}$ and $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.3}Fe_{0.1}$) on the electrode properties were examined. Ag-free and Ag-added Ze-based alloys were prepared by arc melting, crushed mechanically, and subjected to the electrochemical measurement. In $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.4}$ alloy, 0.08 wt% Ag addition to the alloy improved the activation rate. Also Ag addition improved both activation property and discharge capacity in $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.3}Cr_{0.1}$. For these Ag-added alloys, discharge capacities with the change of charge-discharge current density(10mA, 15mA and 30mA) are almost constant. Showing very high rate capability, discharge capacity of $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.3}Fe_{0.1}$ alloy increased by Ag addition to the alloy. When the amount of Ag addition in $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.4}$ alloy increased too much, the electrode properties became worse. Unveiling mechanism of effect of Ag addition is now progressing in our laboratory.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1992.11a
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• pp.39-40
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• 1992

This paper dealt with the manufacturing of binary alloy catalyst and showed simple electrochemical method for determing catalytic activity of oxygen reduction in acid or alkaline electrolyte. The catalyst was prepared by impregnating transition metal salts on platinum or silver particles adsorbed before on carbon paper substrate. The electrochemical characteristics of the catalysts was investigated with carbon paper electrode or PTFE-boned porous electrode and then cathodic current densities and tafel slopes were compared. As a result, of all binary catalysts utilized in this work, Pt-Fe, Pt-Mo showed better oxygen reduction activity than pure platinum catalyst in acid electrolyte and Ag-Fe, Ag-Pt, and Ag-Ni-Bi-Ti catalyst did than pure silver catalyst in alkaline electrolyte. The current density of Pt-Fe electrode in acid electrolyte was one and half times higher than that of Pt electrode(~500mA/$\textrm{cm}^2$ at 0.7VvsNHE).

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.3
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• pp.181-189
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• 2002

A series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22, and 0.30) alloys are prepared and their oystal structure and P-C-T curves are examined. The electrochemical properties of these allqys such as activation conditions, discharge capacity, cycling performance are also investigated. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22 and 0.30) have the C14 Laves phase hexagonal structure. The electrode was activated by the hot-charging treatment. The best activation conditions were the current density 120 mA/g and the hot-charging time 12h at $80^{\circ}C$ in the case of the alloy with x=0.00. The discharge capacity increased rapidly until the fourth cycle and then decreased. The discharge capacity increased again from the 13th cycle, arriving at 234 mAh/g at the 50th cycle. The discharge capacily just after activation decreases with the increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is 157 mAh/g at the current density 120 mA/g. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Fe_{0.15}$ is a good composition with a medium quantity of discharge capacities and a good cycling performance. The ICP analysis of the electrolyte for these electrodes after 50 charge-discharge cycles shows that the concentrations of V and Zr are relatively high. Another series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}M_{0.15}$ (M = Fe, Co, Cu, Mo and Al) alloys are prepared. They also have the C14 Laves phase hexagonal structure. The alloys with M = Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M = Al and Cu. They are 212 and 170 mAh/g, respectivety, at the current density 120mA/g. The $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Co_{0.15}$ alloy is the best one with a relatively large discharge capacity and a good cycling performance.

• Journal of Electrochemical Science and Technology
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• v.13 no.4
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• pp.497-503
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• 2022

Spinel ferrites (Ni_xFe_3-xO₄; x = 0.25, 0.5, 0.75 and 1.0) have been prepared at 550℃ by egg white auto-combustion route using egg white at 550℃ and characterized by physicochemical (TGA, IR, XRD, and SEM) and electrochemical (CV and Tafel polarization) techniques. The presence of characteristic vibration peaks in FT-IR and reflection planes in XRD spectra confirmed the formation of spinel ferrites. The prepared oxides were transformed into oxide film on glassy carbon electrodes by coating oxide powder ink using the nafion solution and investigated their electrocatalytic performance for OER in an alkaline solution. The cyclic voltammograms of the oxide electrode did not show any redox peaks in oxygen overpotential regions. The iR-free Tafel polarization curves exhibited two Tafel slopes (b₁ = 59-90 mV decade^-1 and b₂ = 92-124 mV decade^-1) in lower and higher over potential regions, respectively. Ni-substitution in oxide matrix significantly improved the electrocatalytic activity for oxygen evolution reaction. Based on the current density for OER, the 0.75 mol Ni-substituted oxide electrode was found to be the most active electrode among the prepared oxides and showed the highest value of apparent current density (~9 mA cm^-2 at 0.85 V) and lowest Tafel slope (59 mV decade^-1). The OER on oxide electrodes occurred via the formation of chemisorbed intermediate on the active sites of the oxide electrode and follow the second-order mechanism.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1873-1875
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• 1999

The effects of electrode and matrix in the PAFC were investigated using AC-impedance spectroscopy. The performance of PAFC was determined by changing external electronic load. AC impedance measurement was carried out as functions of phosphoric acid impregnation temperature. operating temperature and matrix coating method using various cathodes ; 20%Pt/C, 20%Pt-Ni/C, 20%Pt-Co-Ni/C, 10%Pt-Fe-Co/C, and 20%Pt-Fe-Co/C From the analysis of measured impedance data, the interfacial resistance decreased with increasing operating temperature. and with decreasing impregnation temperature. As compared with the alloy catalysts, Pt catalyst showed a lower interfacial resistance. This consist with the cell performance.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.4
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• pp.198-205
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• 2016

For the study on the ion exchange of nickel hexacyanoferrate(NiHCNFe) electrode with the several cations, the film of hexacyanoferrate was prepared on the bare nickel surface by the electrochemical and chemical methods in the solution composed with 5mM K3Fe(CN)6 and 100mM KNO3. To compare the capability of the ion exchange of NiHCNFe film electrode, the repeated cyclic voltammograms were measured in the 0.5M cation nitrate solutions at $25^{\circ}C$ and pH7. It was found that the capacity of the electrochemically derivatized NiHCNFe reduced in the rate of 0.5~0.7%/cycle and was nearly exhausted at the 150th potential cycle. Better result was obtained from that the capacity loss of the chemically assembled NiHCNFe was less than 0.02%/cycle for 5,000cycles. Furthermore, the residual capacity was more than 30% at the 5,000th cycle.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.50-51
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• 2002

최근 실온에서 약 40％ 이상의 높은 자기저항(magnetoresistance, MR)을 나타내는 자기 터널 접합(magnetic tunnel junction, MTJ)이 보고되면서 비휘발성 자기메모리로의 응용을 눈앞에 두고 있다.[1]. 이에 본 실험에서는 Substrate / Ta (base electrode) / NiFe / PtMn (AF pinning layer) / CoFe (pinned) / Ru / CoFe (fixed) / Al-O/ CoFe (free) / NiFe (free) / Ta & Ru (Capping Layer)과 같은 MTJ 증착 구조를 사용하여, MTJ의 보다 향상된 특성을 확보하기 위한 노력으로서 Al-O 두께, 어닐링 조건(Field Intensity ＆ Sequence)변화 등을 시도하였다. (중략)

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.44-53
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• 1994

A study on the iron electrode which is a good material for alkaline battery because of its superior characteristics including high theoretical capacity density, low toxicity, low cost and inexhaustible supply was performed to develop high performance nickel-iron secondary battery. The characteristics of chrage-discharge reaction were examined by cyclic voltammetry technique SEM and XRD analysis. The capacity of the test electrodes was determined by the costant current charge-discharge method. It was found that the purity and particle size of iron material were the major determinant factors of electrode capacity. With the addition of $Na_2S$ into the electrolyte the capacity of electrode was increased about 20 % caused by the prevention of passivation and the increase of hydrogen overpotential. The stability and capacity of electrode were increased with the use of Ni-fibrex and foamed Ni collectors and also depended on the sintering temperature. The capacity of electrode was 350 mAh/g(0.2 C) which corresponded to 36% utility.