• Journal of Electrochemical Science and Technology
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• 제14권3호
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• pp.243-251
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• 2023

Developing oxygen evolution reaction (OER) electrocatalysts is essential to accomplish viable CO₂ and water electrolysis. Herein, we report the fabrication and OER performance of Ni-foam (NF)-immobilized Ni₆ nanoclusters (NCs) (Ni₆/NF) prepared by a dip-coating process. The Ni₆/NF electrode exhibited a high current density of 500 mA/cm² for the OER at an overpotential as low as 0.39 V. Ni₆/NF exhibited high durability in an alkaline solution without corrosion. Electrokinetic studies revealed that OER can be easily initiated on Ni6 NC with fast electron-transfer rates. Finally, we demonstrated stable CO₂-to-CO electroreduction using an NC-based zero-gap CO₂ electrolyzer operated at a current density of 100 mA/cm² and a full-cell potential of 2.0 V for 12 h.

• 한국결정성장학회지
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• 제31권2호
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• pp.96-101
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• 2021

Developing effective and earth-abundant electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is critical for the commercialization of a water splitting system. In particular, the overpotential of the OER is relatively higher than the HER, and thus, it is considered that one of the important methods to enhance the performance of the electrocatalyst is to reduce the overpotential of the OER. We report effects of incorporation of metalloid into Ni(OH)2 microcrystal on electrocatalytic activities. In this study, Te incorporated Ni(OH)2 (��Te-Ni(OH)2) were grown on three-dimensional porous NF by a facile solvothermal method with �� = 1, 3 and 5. Homogeneous microplate structure on the NF was clearly observed for the Ni(OH)2/NF and ��Te-Ni(OH)2/NF samples. However, irregular and collapsed nanostructures were found on the surface of nickel foam when Te precursor ratio is (��) over 3. Electrocatalytic OER properties were analysed by Linear sweep voltammetry (LSV) and Electrochemical impedance spectroscopy (EIS). The amount of Te incorporation used in the electrocatalytic reaction was found to play a crucial role in improving catalytic activity. The optimum Te amount (��) introduced into the Ni(OH)2/NF was discussed with respect to their OER performance.

• 한국표면공학회지
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• 제56권4호
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• pp.243-249
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• 2023

Urea oxidation reaction (UOR) via electrochemical oxidation process can replace oxygen evolution reaction (OER) for green hydrogen production since UOR has lower thermodynamic potential (0.37 V_RHE) than that of OER (1.23 V_RHE). However, in the case of UOR, 6 electrons are required for the entire UOR. For this reason, the reaction rate is slower than OER, which requires 4 electrons. In addition, it is an important challenge to develop catalysts in which both oxidation reactions (UOR and OER) are active since the active sites of OER and UOR are opposite to each other. We prove that among the NiFe₂O₄ nanoparticles synthesized by the hydrothermal method at various synthesis temperatures, NiFe₂O₄ nanoparticle with properly controlled particle size and crystallinity can actively operate OER and UOR at the same time.

• 공업화학
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• 제34권2호
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• pp.180-185
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• 2023

물의 전기 분해 효율을 향상시키기 위해 산소발생반응(OER)의 반응 속도를 가속화하며 고성능과 장기 안정성을 가진 OER 전기촉매 개발이 필수적이다. 본 연구에서는 고효율의 OER 전기촉매를 합성하기 위해 중공 금속-유기골격체 (MOF)로부터 유도된 루테늄-코발트 산화물 촉매를 개발하였다. 합성된 촉매는 루테늄의 표면 노출을 증대시킴으로 낮은 Tafel 기울기와 10 mA/cm²의 전류밀도에서 386 mV의 낮은 과전위가 관찰되었다. 또한 상용 RuO₂ 촉매 대비 높은 질량 활성과 안정성을 보여, 귀금속 촉매를 대체할 수 있을 것으로 기대된다.

• 한국압력기기공학회 논문집
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• 제9권1호
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• pp.35-39
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• 2013

The Operating Experience Report(OER) has written about the event and accident happened at a Nuclear Power Plant(NPP). The purpose of publishing the OER is to prevent the similar event or accident repeatedly by spreading the experience of a single plant to other plants personnel. Before initiating the analysis mentioned in this paper, 2,298 review reports for the same number of OER published from 2007 to June 2012 have been written to achieve the correct and objective statistics. The analysis introduced in this paper is performed with the various factors such as year, plant type, equipment, type of work, root-cause. The root-cause analysis is showed that the equipment problem is the major factor in domestic NPPs, but on the other hand human-error is the main part of the foreign NPPs. Moreover, while the number of the man-made event is decreasing, the equipment-made event is rapidly increasing in domestic NPPs.

• 한국재료학회지
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• 제32권8호
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• pp.339-344
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• 2022

The lattice oxygen mechanism (LOM) is considered one of the promising approaches to overcome the sluggish oxygen evolution reaction (OER), bypassing -OOH^* coordination with a high energetic barrier. Activated lattice oxygen can participate in the OER as a reactant and enables O^*-O^* coupling for direct O₂ formation. However, such reaction kinetics inevitably include the generation of oxygen vacancies, which leads to structural degradation, and eventually shortens the lifetime of catalysts. Here, we demonstrate that Se incorporation significantly enhances OER performance and the stability of NiFe (oxy)hydroxide (NiFe) which follows the LOM pathway. In Se introduced NiFe (NiFeSe), Se forms not only metal-Se bonding but also Se-oxygen bonding by replacing oxygen sites and metal sites, respectively. As a result, transition metals show reduced valence states while oxygen shows less reduced valence states (O^-/O₂^2-) which is a clear evidence of lattice oxygen activation. By virtue of its electronic structure modulation, NiFeSe shows enhanced OER activity and long-term stability with robust active lattice oxygen compared to NiFe.

• 한국결정성장학회지
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• 제33권2호
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• pp.78-82
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• 2023

The oxygen evolution reaction (OER) is the primary challenge in renewable energy storage technologies, specifically electrochemical water splitting for hydrogen generation. We report effects of Mo doping into Ni layered double hydroxide (Ni-LDH) microcrystal on electrocatalytic activities. In this study, Mo doped Ni-LDH were grown on three-dimensional porous nicekl foam (NF) by a facile solvothermal method. Homogeneous LDH structure on the NF was clearly observed. However, the surface microstructure of the nickel foam began to be irregular and collapsed when Mo precursor is doped. Electrocatalytic OER properties were analyzed by Linear sweep voltammetry (LSV) and Electrochemical impedance spectroscopy (EIS). The amount of Mo doping used in the electrocatalytic reaction was found to play a crucial role in improving catalytic activity. The optimum Mo amount introduced into the Ni LDH was discussed with respect to their OER performance.

• Educational Technology International
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• 제13권1호
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• pp.27-48
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• 2012

In this paper we are comparing how the OER (open educational resources) are developed in Higher Education in Finland and South Korea. We also present a comparison model for further studies. Essential findings based on our comparison are that in both countries there are many best practices of use of the OER and open learning. Open educational resources have great potential and their use can ensure quality teaching and learning. The activity has not inspired the great mass of higher education teachers in Finland and Korea. Traditionally, a teacher's job is working alone, and so a new operational culture is required. Our comparison indicates that numerous questions, fears and problems and cultural differences are also related to the thematic. There is an evident need for a new kind of strategic leadership, a new kind of teaching and learning culture and a doing together and production ideology for the method to spread. Based on our study the following interlinked elements of OER seem to be pivotal: changes to pedagogies, technology and operational culture; educational policy intention; and attitude to culture. Lastly, comparison frame by OER practice model is developed.

• 한국결정성장학회지
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• 제34권3호
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• pp.92-97
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• 2024

수소 생산을 위한 물 분해 시스템의 효율성을 높이려면 산소 발생 반응(OER, Oxygen Evolution Reaction)에서 촉매로 인해 발생하는 전기화학 반응의 높은 과전압을 감소시켜야 한다. 그중 전이금속을 포함하는 LDH(Layered Double Hydroxide)와 같은 화합물은 현재 사용되고 있는 백금 등의 귀금속을 대체할 수 있는 촉매 소재로 주목받고 있다. 본 연구에서는 저렴한 금속 다공성 물질인 니켈 폼을 지지체로 사용하였고, 수열합성 공정을 통해 NiCo LDH 나노결정을 합성하였다. 또한, OER 특성을 향상시키기 위해 Mo를 도핑하여 합성한 Mo 도핑된 NiCo LDH 나노결정 시료의 형태, 결정구조, 물분해 특성의 변화를 관찰하였다.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.96-104
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• 2023

Synergistically increased oxygen evolution reaction (OER) of manganese oxide (MnO₂) catalyst is introduced with surface-modified halloysite nanotube (Fe₃O₄-HNTs) structure. The flake shaped MnO₂ catalyst is attached on the nanotube template (Fe₃O₄-HNTs) by series of wet chemical and hydrothermal method. The strong interaction between MnO₂ and Fe₃O₄-HNTs maximized active surface area and inter-connectivity for festinate charge transfer reaction for OER. The synergistical effect between Fe₃O₄ layer and MnO₂ catalyst enhance the Mn³⁺/Mn⁴⁺ ratio by partial replacement of Mn ions with Fe. The relatively increased Mn³⁺/Mn⁴⁺ ratio on MnO₂@FHNTs induced 𝜎^* orbital (e_g) occupation close to single electron, improving the OER performances. The MnO₂@FHNTs catalyst exhibited the reduced overpotential of 0.42 V (E vs. RHE) at 10 mA/cm² and Tafel slope of (99 mV/dec), compared with that of MnO₂ with unmodified HNTs (0.65 V, 219 mV/dec) and pristine MnO₂ (0.53 V, 205 mV/dec). The present study provides simple and innovative method to fabricate nano fiberized OER catalyst for a broad application of energy conversion and storage systems.