• 한국결정성장학회지
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• 제31권3호
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• pp.143-148
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• 2021

Alkaline oxygen evolution reaction (OER) electrocatalysts have been widely studied for improving the efficiency and green hydrogen production through electrochemical water splitting. Transition metal-based electrocatalysts have emerged as promising materials that can significantly reduce the hydrogen production costs. Among the available electrocatalysts, transition metal-based layered double hydroxides (LDHs) have demonstrated outstanding OER performance owing to the abundant active sites and favorable adsorption-desorption energies for OER intermediates. Currently, cobalt doped nickel LDHs (NiCo LDHs) are regarded as the benchmark electrocatalyst for alkaline OER, primarily owing to the physicochemical synergetic effects between Ni and Co. We report effects of heat-treatment of the as-grown NiCo LDH on electrocatalytic activities in a temperature range from 250 to 400℃. Electrocatalytic OER properties were analysed by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The heat-treatment temperature was found to play a crucial role in catalytic activity. The optimum heat-treatment temperature was discussed with respect to their OER performance.

• 대한화학회지
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• 제58권2호
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• pp.205-209
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• 2014

Hematite iron oxide (${\alpha}$-$Fe_2O_3$) nanowalls were fabricated on aluminum substrate by a facile solvent-assisted hydrothermal oxidation process. The XRD and EDS patterns indicate that the sample has a rhombohedral phase of hematite $Fe_2O_3$. FE-SEM, TEM, HR-TEM, SA-ED were employed to characterize the resulting materials. $N_2$ adsorption-desorption isotherms was used to study a BET surface area. Their capability of catalytic degradation of titan yellow GR azo dye with air oxygen in aqueous solution over $Fe_2O_3$ catalysts was studied. The result indicates that the as-prepared product has a high catalytic activity, because it has a larger surface area. Langmuir and Freundlich isotherms of adsorption dye on the catalysts surface were investigated and the decomposition of titan yellow GR follows pseudo-first order kinetic.

• 한국전기전자재료학회논문지
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• 제22권4호
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• pp.318-322
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• 2009

In this paper, to establish growth technology of ZnO:Al thin films at low temperature applied to photoelectronic devices, ZnO:Al were prepared by RF magnetron sputtering on glass substrate at room temperature using different RF power with subsequent annealing process at different temperature in $H_2$ ambient. The resistivity of hydrogen-annealed ZnO:Al thin film at temperature of $300^{\circ}C$ was reduced to $8.32{\times}10^{-4}{\Omega}cm$ from $9.44{\times}10^{-4}{\Omega}cm$ which was optimal value for as-grown films. X-ray photoelectron spectroscopy(XPS) revealed that improved electrical properties are ascribed to desorption of the negatively charged oxygen species from the grain boundary surfaces by the hydrogen annealing process.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1951-1955
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• 2014

Catalytic pyrolysis of Geodae-Uksae 1, a kind of miscanthus found in Korea, was carried out over mesoporous MCM-48 catalysts. For rapid product analysis and catalyst evaluation, pyrolysis-gas chromatography/mass spectrometry was used. X-ray diffraction, nitrogen sorption, pyridine adsorbed Fourier transform infrared, and NH3 temperature programmed desorption were utilized to analyze the properties of the catalysts. Compared to non-catalytic reaction, catalytic upgrading over mesoporous Al-MCM-48 catalysts produced a higher-quality bio-oil with a high stability and low oxygen content. Al-MCM-48 exhibited higher deoxygenation ability than Si-MCM-48 due to its higher acidity.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.184-186
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• 2009

Composites of LSCF($La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ and CGO(gadolinium doped ceria) is an efficient candidate cathode material with CGO electrolytes. In this study, LSCF with exact perovskite structure was synthesized by using solid state reaction(SSR) method. The optimized temperature to synthesize $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ with rhombohedral structure. was $1100^{\circ}C$. The polarization resistance of the LSCF/CGO(50:50 wt.%) was smaller than those of other composite cathodes. The analysis of the EIS data of LSCF/CGO suggests that the diffusion and adsorption-desorption of oxygen can be the key process in the cathodic reaction of SOFC using LSCF/CGO as cathode material.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.475-479
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• 1996

At present studies, we are going to suggest the new type of Perovskite derived catalysts which modify the defects of transition metals impregnated. Perovskite type catalyst is a typical mixed metal oxides, and there are "defect"s (from like that oxygen, cation, crystallic structure) were made by difference from composition, preparing method and so forth. And because this, its electro-magnetic character could be much changed. By using this phenomena, it could utilize the modification of adsorption/desorption characters as well as the catalytic activities in NOx reduction. Because perovskite type catalyst can exchange the metal of the each lattice site freely and it is possible to represent the peculiar.

• 공업화학
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• 제5권2호
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• pp.189-198
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• 1994

초고진공하에서 열탈착 실험에 의하여 오산화바나듐 촉매상에서 일산화탄소와 메탄올의 홉착특성을 연구하였다. 일산화탄소는 오산화바나듐 촉매표면의 격자산소 결함을 갖는 바나듐이온이나 바나듐이온에 결합된 이중결합성 산소에 흡착하였다. 격자산소 결함을 갖는 바나듐이온에 흡착한 일산화탄소는 380K에서 탈착되었으며, 바나듐이온에 결합된 이중결합성 산소에 흡착한 일산화탄소는 격자산소와 결합하여 탄산기의 형태를 형성한 후 이산화탄소로 탈착되면서 촉매 표면을 환원시켰다. 선흡착되거나 후흡착되는 산소에 의하여, 탄산기의 형태로 흡착하는 일산화탄소의 흡착량은 증가하였다. 오산화바나듐 촉매상에서 메탄올을 흡착시킨 후 메탄올, 포름알데히드, 일산화탄소, 수소 등의 열탈착실험에 의하여 메탄올의 흡착특성을 연구하였다. 메탄올은 298 K에서 오산화바나듐 촉매상에 methoxy와 hydroxyl기를 형성하면서 분해흡착하였다.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.116-123
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• 2007

[ $La_{0.5}Ce_{0.5}Co_{1-x}Cu_xO_{3-{\alpha}}$ ](X=0, 0.1, 0.3, 0.5) perovskites were prepared by coprecipitation method at pH 7 or pH 11 and its catalytic activity of selective CO oxidation was investigated. The characteristics of these catalysts were analyzed by $N_2$ adsorption, X-ray diffraction(XRD), SEM, $O_2$-temperature programmed desorption(TPD). The pH value at a preparation step made effect on particle morphology. The smaller particle was obtained with a condition of pH 7. The better catalytic activity was observed using catalysts prepared at pH 7 than pH 11. The maximum CO conversion of 98% was observed over $La_{0.5}Ce_{0.5}Co_{0.7}Cu_{0.3}O_{3-{\alpha}}$ at $320^{\circ}C$. Below $200^{\circ}C$, the most active catalyst was $La_{0.5}Ce_{0.5}Co_{0.9}Cu_{0.1}O_{3-{\alpha}}$, of which conversion was 92% at $200^{\circ}C$. By the substitution of Cu, the evolution of ${\alpha}$-oxygen was remarkably enhanced regardless of pH value at preparation step according to $O_2$-TPD. Among the different ${\alpha}$-oxygen species, the oxygen species evolved between $400^{\circ}C$ and $500^{\circ}C$, gave the better catalytic performance for selective CO oxidation including $La_{0.5}Ce_{0.5}CoO_3$ in which Cu was absent.

• 청정기술
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• 제2권1호
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• pp.60-68
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• 1996

고정층 반응기에서 망간광석을 이용하여 저농도의 일산화탄소 산화제어반응에 대하여 고찰하였다. 고려된 실험변수는 일산화탄소 농도 (500ppm~10000ppm), 산소 농도(500ppm~99.8%)와 촉매의 온도($50{\sim}750^{\circ}C$)이다. 또한 망간광석의 특성은 Thermogravimetric Analysis(TGA), 일산화탄소에 의한 환원, Temperature Programmed Reduction(TPR)실험을 이용하여 규명하였다. 망간광석의 일산화탄소 산화력은 순수이산화망간에 비해서 단위 면적당 높은 산화력과 $750^{\circ}C$까지 가열된 후에도 산화력이 유지될 수 있는 안정된 촉매작용을 보였다. Temperature Programmed Desorption(TPD), TPR 실험과 TG 등의 분석결과 산소의 농도가 낮거나 무산소하에서 망간광석의 격자내 산소가 쉽게 제공될 수 있음을 알 수 있었다. 일산화탄소의 농도가 500~3500ppm일 때 일산화탄소의 반응차수는 0.701이며 3500~10000ppm구간에서 일산화탄소의 농도에 무관한 0차 반응이었다.

• Journal of Electrochemical Science and Technology
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• 제12권1호
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• pp.137-145
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• 2021

Among the non-precious metal catalysts, iron-nitrogen doped carbon (Fe-N/C) catalysts have been recognized as the most promising candidates for an alternative to Pt-based catalysts for the oxygen reduction reaction (ORR) under alkaline and acidic conditions. In this study, the nano replication method using mesoporous silica, which features tunable primary particle sizes and shape, is employed to prepare the mesoporous Fe-N/C catalysts with different shapes. Platelet SBA-15, irregular KIT-6, and spherical silica particle (SSP) were selected as a template to generate three different kinds of shapes of the mesoporous Fe-N/C catalyst. Physicochemical properties of mesoporous Fe-N/C catalysts are characterized by using small-angle X-ray diffraction, nitrogen adsorption-desorption isotherms, and scanning electron microscopy images. According to the electrochemical evaluation, there is no morphological preference of mesoporous Fe-N/C catalysts toward the ORR activity with half-cell configuration under alkaline electrolyte. By implementing X-ray photoelectron spectroscopy analysis of Fe and N atoms in the mesoporous Fe-N/C catalysts, it is possible to verify that the activity towards ORR highly depends on the portions of "Fe-N" species in the catalysts regardless of the shape of catalysts. It was suggested that active site distribution in the Fe-N/C is one important factor towards ORR activity.