• 대한화학회지
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• 제28권5호
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• pp.271-278
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• 1984

염기성 용액에서 기계적으로 연마한 고순도 철의 전위를 환원 전위로부터 부동화 전위로 급격히 변화시켜서 부동화 막이 전극표면에 형성되게 하면서 철의 반사율 변화와 타원편광반사법(Ellipsometry) 측정을 하였다. 철 표면이 부동화 될때 일어나는 반사광의 편광 파라메터(${\Delta},\;{\psi}$)와 반사율(R) 변화를 자동화된 타원편광반사계로 기록하였고, 이로부터 철을 부동화 상태에 들어가게 하는 표면막의 두께(${\tau}$)와 광학상수(n, k)들의 변화하는 값을 계산할 수 있었다. 광학상수 값들로 나타나는 막의 성질이 시간에 따라 급격한 전이를 하는 것은 관찰되지 않았으며, 비교적 짧은 시간(수초)내에 정상 상태 값에 접근하였다. 효과적으로 부동화를 일으키는 막의 두께는 $14\;{\sim}\;23{\AA}$의 범위에 있었다. 형성된 부동화 막은 용액의 pH가 큰 경우에는 얇고 치밀한 구조를 가진 것으로 보이며, pH가 작은 경우에는 두께는 두껍지만 pH가 큰 경우보다 덜 치밀한 부동화 막이 형성되는 것으로 보였다. 이들 부동화 막은 약간의 흡광성을 가지는 것으로 나타났다.

• 한국수소및신에너지학회논문집
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• 제3권2호
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• pp.25-33
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• 1992

With the aim to obtain $TiO_2$ films with an increased photorespones and absorbance in the visible region of the solar spectrum, the direct oxidation of titanium alloys were performed. In this study, $Ti-Ga_2O_3$ alloy was prepared by mixing, pressing and arc melting of appropriate amounts of titanium and $Ga_2O_3$ powder. Electrochemical measurements were performed in three electrode cell using electrolyte of 1M NaOH solution. The oxide films on $Ti-Ga_2O_3$ alloy was composed of $Ti_2O$, TiO, $TiO_2$, $Ga_2TiO_5$. The free energy efficiency (${\eta}e$) of $Ti-Ga_2O_3$ oxide films had 0.8~1.3 % and were increased with the increase of $Ga_2O_3$ content up to 10wt %. The onset potential ($V_{on}$) had -0.8V~0.9V ranges and were shifted to anodic direction with the increase of $Ga_2O_3$ content. The spectral response of Ti-$Ga_2O_3$ oxides were similar to the response of the $TiO_2$ and their $E_g$ were observed to 2.90~3.0eV. Variations of onset potential($V_{on}$) associated with electrolyte pH were -59mV/pH. This probably reflects the nature of the bonding of $OH^-$ ion to the $TiO_2$ surface, a common phenomena in the transition-metal oxides.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 수소연료전지공동심포지움 2004논문집
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• pp.103-108
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• 2004

The present paper relates to an apparatus in which all carbonaceous material such as coal, oil, plastics and any substance having carbon atoms as part of its constituents are reformed(gasified) into syngas at temperature above $1,200^{\circ}C$(KR patent No.0391121, and PCT/KR2001/01717 and PCT/KR2004/001020). It comprises a single-stage reforming reactor without catalyst and a syngas burner as shown in Fig.2. syngas is combusted with $O_2$ gas in the syngas bunter to produce $M_2O$ and $CO_2$ gas with exothermic heat. Reaction products are introduced into the reforming reactor, reaction heat from syngas burner elevate the temperature of reactor above $1,200^{\circ}C$, and reaction products reduce carbonaceous material down to CO and $H_2$ gases. Reactants and heat necessary for the reaction are provided through the syngas burner only, Neither $O_2$ gas nor steam are injected into the reforming reactor. Reformer is made of ceramic inner lining and sst outer casing. Multiple syngas burners may be connected to the reforming reactor in order to increase the syngas output, and a portion of the product syngas is recycled into syngas burner. The present reformer as shown in Fig.2 is suitable to gasify carbonaceous wastes without secondary pollutants formed from oxidation. Further, it can be miniaturized to accompany a fuel cell system as shown in Fig.3 The output syngas may be used to drive a fuel cell and a portion of electrical power generated in a fuel cell is used to heat a compact reformer up to $1,200^{\circ}C$ so that gas/liquid fossil fuel can efficiently reformed into syngas. The fuel cell serves as syngas burner in Fig.2. The reformation reaction is sustained through recycling a portion of product syngas into a fuel cell and using a portion of electric power generated to heat the reformer for continuous operation. Such reforming reactor may be miniaturized into a size of PC, then you have a Personal Reformer(PR).

• 한국표면공학회지
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• 제50권5호
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• pp.322-331
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• 2017

Hydrogen evolution reaction(HER) was studied over $Ni_4Cr$ nanofibers(NFs) prepared by electrospinning method and oxidation/reduction heat treatment for alkaline water electrolysis. The physicochemical and electrochemical properties such as average diameter, lattice parameter, HER activity of synthesized $Ni_4Cr$ NFs could be modified by proper electrospinning process condition and reduction temperature. It was shown that $Ni_4Cr$ NFs had average diameter from 151 to 273 nm. Also, it exhibited the overpotential between 0.419 V and 0.526 V at $1mA/cm^2$ and Tafel slope of -334.75 mV to -444.55 mV per decade in 1 M KOH solution. These results indicate that $Ni_4Cr$ NFs with reduction heat treatment at $600^{\circ}C$ show thinnest diameter and highest HER activity among the other catalysts.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.481-481
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• 2007

This work describes the effect of the number of roll pressing and the composition of carbon black on the electric and mechanical properties of carbon-PTFE electrode, in which composition is MSP 20 : carbon black: PTFE = 95-x : x : 5 wt.%. It was found that the best electric and mechanical properties were obtained in sheet electrode roll-pressed for about 15 times and in sheet electrode, in which composition is MSP 20 : carbon black: PTFE = 80 : 15 : 5 wt.%. These behaviors could be explained by the network structure of PTFE fibrils and conducting paths linked with carbon blacks, respectively. On the other hand, cell capacitor using the sheet electrode with 15 wt.% of carbon black attached on aluminum current collector with the electric conductive adhesive, in composition is carbon black : CMC = 70 : 30 wt.%, has exhibited the best rate capability in the current range of $0.5mA/cm^2$ $100mA/cm^2$ and the lowest equivalent series resistance.

• Bulletin of the Korean Chemical Society
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• 제21권6호
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• pp.588-594
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• 2000

Structural changes of an iron phthalocyanine (FePC) monolayer induced by adsorption and externally applied potential on high area carbon surface have been investigated in situ by iron K-edge X-ray absorption fine structure (XAFS) in 0.5 M $H_2S0_4.$ Fine structures shown in the X-ray absorption near edge structure (XANES) for microcrystalline FePC decreased upon adsorption and further diminished under electrochemical conditions. Fe(II)PC(-2) showed a 1s ${\rightarrow}$ 4p transition as poorly resolved shoulder to the main absorption edge rather than a distinct peak and a weak 1s ${\rightarrow}$ 3d transition. The absorption edge position measured at half maximum was shifted from 7121.8 eV for Fe(lI)PC(-2) to 7124.8 eV for $[Fe(III)PC(-2)]^+$ as well as the 1s ${\rightarrow}$ 3d pre-edge peak being slightly enhanced. However, essentially no absorption edge shift was observed by the 1-electron reduction of Fe(Il)PC(-2), indicating that the species formed is $[Fe(II)PC(-3)]^-$. Structural parameters were obtained by analyzing extended X-ray absorption fine structure (EXAFS) oscillations with theoretical phases and amplitudes calculated from FEFF 6.01 using multiple-scattering theory. When applied to the powder FePC, the average iron-to-phthalocyanine nitrogen distance, d(Fe-$N_p$) and the coordination number were found to be 1.933 $\AA$ and 3.2, respectively, and these values are the same, within experimental error, as those reported ( $1.927\AA$ and 4). Virtually no structural changes were found upon adsorption except for the increased Debye-Wailer factor of $0.005\AA^2$ from $0.003\AA^2.$ Oxidation of Fe(II)PC(-2) to $[Fe(III)PC(-2)]^+$ yielded an increased d(Fe-Np) (1 $.98\AA)$ and Debye-Wailer factor $(0.005\AA^2).$ The formation of $[Fe(II)PC(-3)]^-$, however, produced a shorter d(Fe-$N_p$) of $1.91\AA$ the same as that of crystalline FePC within experimental error, and about the same DebyeWaller $factor(0.006\AA^2)$.

• Korean Chemical Engineering Research
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• 제57권3호
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• pp.425-431
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• 2019

As rechargeable metal-air batteries will be ideal energy storage devices in the future, an active cathode electrocatalyst is required with bi-functionality on both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during discharge and charge, respectively. Here, a class of perovskite cathode catalyst with a micro-tubular structure has been developed by controlling bi-functionality from different Ru and Ni dopant ratios. A micro-tubular structure is achieved by the activated carbon fiber (ACF) templating method, which provides uniform size and shape. At the perovskite formula of $LaCrO_3$, the dual dopant system is successfully synthesized with a perfect incorporation into the single perovskite structure. The chemical oxidation states for each Ni and Ru also confirm the partial substitution to B-site of Cr without any changes in the major perovskite structure. From the electrochemical measurements, the micro-tubular feature reveals much more efficient catalytic activity on ORR and OER, comparing to the grain catalyst with same perovskite composition. By changing the Ru and Ni ratio, the $LaCr_{0.8}Ru_{0.1}Ni_{0.1}O_3$ micro-tubular catalyst exhibits great bi-functionality, especially on ORR, with low metal loading, which is comparable to the commercial catalyst of Pt and Ir. This advanced catalytic property on the micro-tubular structure and Ru/Ni synergy effect at the perovskite material may provide a new direction for the next-generation cathode catalyst in metal-air battery system.

• 한국재료학회지
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• 제32권1호
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• pp.14-22
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• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• 대한환경공학회지
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• 제38권12호
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• pp.647-655
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• 2016

Lead dioxide ($PbO_2$)는 전기화학적 고도산화공정(electrochemical advanced oxidation process, EAOP)에서 hydroxyl radical ($^{\bullet}OH$) 발생에 기반한 유기오염물 분해에 효과적인 전극물질이다. $PbO_2$ 전극의 대표적인 제조방법인 전기화학적 증착법(electrodeposition)의 주요 인자로는 전류/전압세기, 온도, 반응시간, Pb(II)의 농도, 전해질 종류 및 농도가 있다. 본 연구에서는 $Ti/PbO_2$ 산화전극을 전기화학적 증착법을 통해 전류인가 시간, 전류밀도, 온도, $HNO_3$ 전해질 농도를 각각 조절하여 제조하였고, $^{\bullet}OH$ 검출물질인 p-Nitrosodimethylaniline (RNO)의 전기화학적 탈색 측면에서 $^{\bullet}OH$ 발생에 대한 $PbO_2$ 증착인자의 영향을 조사하였다. 주요 결과로, $PbO_2$의 $^{\bullet}OH$ 발생 성능은 $PbO_2$ 증착과정에서 대체로 전류인가 시간이 길어질수록(1-90 min), 전류밀도가 감소할수록($0.5-50mA/cm^2$), 증착온도가 증가할수록($5-65^{\circ}C$), $HNO_3$ 전해질 농도(0.01-1.0 M)가 감소할수록 향상되었다. 특히, 0.01 M의 낮은 $HNO_3$ 농도 상에서 $20mA/cm^2$ 전류를 10분 이상 인가하여 증착시킨 $PbO_2$에서$^{\bullet}OH$ 발생이 가장 촉진되었다. RNO 탈색속도 측면에서 가장 성능이 좋은 $PbO_2$와 저조한 $PbO_2$ 사이에 최대 41% 정도 차이가 나타났다. $PbO_2$의$^{\bullet}OH$ 발생 성능을 결정짓는 특성으로 $PbO_2$ 층 전도도, Ti 기판 산화, $PbO_2$ 결정크기를 고려한 결과, $PbO_2$ 층의 전도도 및 Ti 기판의 산화가 $^{\bullet}OH$ 발생에 주요하게 영향을 미치는 것으로 확인되었다. $PbO_2$ 층의 전도도 향상과 Ti 표면 산화 억제로 인한 $Ti/PbO_2$ 계면에서 전도도 향상이 $^{\bullet}OH$ 발생을 촉진시키는 효과를 가져왔다. 그리고 일부 전극에서는 표면에서 $PbO_2$ 결정 크기 증가가 $^{\bullet}OH$ 발생을 저감시키는 역할을 하였다.

• 공업화학
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• 제18권3호
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• pp.205-212
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• 2007

본 연구는 polyacrylonitrile (PAN)를 dimethyl formamide (DMF)에 용해시켜 전압조건을 8~20 kV, PAN 농도조건을 5~15 wt%, 그리고 tip-to-collector distance (TCD)를 15 cm로 다양한 조건에서 전기방사를 실시하였다. 나노섬유는 $250^{\circ}C$에서 1 h 동안 안정화시켰으며, $800{\sim}1000^{\circ}C$에서 1 h 동안 탄화시켰다. 안정화와 탄화 전후의 나노섬유의 구조 특성은 FT-IR 장비를 이용하여 연구하였으며 나노섬유의 직경분포와 모폴로지 특성을 알기 위해서 SEM 분석장비를 이용하였다. 나노섬유웹의 전기화학적 특성은 순환전류 전압곡선 특성 실험을 통해 고찰하였다. 실험 결과로부터 전기방사한 나노섬유의 직경의 크기는 일반적으로 방사용액의 농도와 인가전압에 영향을 받는다는 것을 확인할 수 있었으며 섬유의 평균 직경은 고분자의 농도 10 wt% 이상 증가함에 따라 감소하며 15 kV의 전압과 15 cm의 TCD 조건에서 섬유의 직경분포가 균일하고 평균직경이 작은 것으로 나타났다.