• 전기화학회지
• /
• 제13권1호
• /
• pp.45-49
• /
• 2010

The rechargeable Zn-air battery is considered as one of the potential candidates for the next generation secondary batteries due to its many advantages. However, its further applications and commercialization have been limited by the complexity of the reactions on air electrode which are oxygen reduction and evolution reactions (ORR/OER) upon discharging and charging processes, respectively. In the present study, lanthanum was impregnated into a commercial Pt/C gas diffusion electrode, and it clearly verified significantly enhanced cycling stability and reversibility. The results presented in this study show the possibility of repeated charge/discharge processes for Zn-air batteries with a La-loaded air electrode, and they demonstrate the potential as a promising next generation secondary battery.

• 한국수소및신에너지학회논문집
• /
• 제27권5호
• /
• pp.471-477
• /
• 2016

In this research, the Ir supported $TiO_2$ (P25) catalyst was prepared by precipitation method for oxygen evolution reaction. The $Ir/TiO_2$ catalyst was synthesised by reduction reaction using reducing agent. Physiochemical characterizations of synthesized $Ir/TiO_2$ catalyst was studied by means of SEM, EDS mapping, TEM and XRD. The Electrochemical characterizations were tested by using the technique of CV and LSV by RDE and Potentiostat. Physicochemical properties were characterized with XRD where Iridium metal morphology and Ir(111) and Ir(222) peaks were founded. $Ir0.2Ru0.8O_2$ exhibited higher OER activity than $Ir0.5Ru0.5O_2$ followed by $Ir/TiO_2$ and $IrO_2$.

• 한국재료학회지
• /
• 제28권7호
• /
• pp.428-434
• /
• 2018

Hydrogen evolution on a steel surface and subsequent hydrogen diffusion into the steel matrix are evaluated using an electrochemical permeation test with no applied cathodic current on the hydrogen charging side. In particular, cyclic operation in the permeation test is also conducted to clarify the corrosion-induced hydrogen evolution behavior. In contrast to the conventional perception that the cathodic reduction reaction on the steel in neutral aqueous environments is an oxygen reduction reaction, this study demonstrates that atomic hydrogen may be generated on the steel surface by the corrosion reaction, even in a neutral environment. Although a much lower permeation current density and significant slower diffusion kinetics of hydrogen are observed compared to the results measured in acidic environments, they contribute to the increase in the embrittlement index. This study suggests that the research on hydrogen embrittlement in ultra-strong steels should be approached from the viewpoint of corrosion reactions on the steel surface and subsequent hydrogen evolution/diffusion behavior.

• 공업화학
• /
• 제7권2호
• /
• pp.280-288
• /
• 1996

여러 가지 전착 조건에서 티타늄 기판상에 이산화납을 전착시킨 전극을 사용하여 전해질 용액 중에서 오존을 발생시킬 경우 전착된 이산화납의 결정표면 양상이 오존발생 전류효율에 미치는 영향과 이산화납 전극의 표면구조 변화를 고찰하였다. 또한 백금 디스크전극 위에 이산화납을 전착시킨 회전전극을 이용하여 산소전이반응이 오존발생에 미치는 영향과 오존발생용 전극으로 개발하기 위해 이산화납의 내식성과 오존발생 최적 전류밀도도 검토하였다. 전착한 이산화납의 결정표면 입자가 크고 결정성이 좋은 전극일수록 오존발생 전류효율이 높았으며 이러한 오존발생용 이산화납 전극을 전착시키기 위한 최적전류밀도는 $50mA/cm^2$이었으며 전착용액에 글리세린을 소량 첨가하면 오존발생에 유리한 결정구조를 갖는 이산화납이 전착되었다. 또한 $10mA/cm^2$ 이하의 너무 낮거나 $100mA/cm^2$ 이상의 너무 높은 전류밀도에서는 오존발생 성능이 떨어지고 소지금속에 대한 접착성이 좋지 않은 전극이 만들어 졌다. 새로 만들어진 이산화납전극을 오존발생용으로 사용할 때 사용 초기 단계에서 이산화납전극의 표면구조 변화가 일어나며 이는 오존발생에 유리한 효과를 가져왔다. 타원소를 도핑시킨 이산화납 전극에서는 오존발생보다 산소발생 반응이 활발하게 일어나 오존발생은 산소발생의 중간 단계를 거치지 않고 산소발생과는 경쟁적으로 일어나는 것으로 추정되며 $0.7{\sim}0.8A/cm^2$의 전류밀도에서 최대의 오존발생 전류효율을 나타내었다.

• 한국수소및신에너지학회논문집
• /
• 제26권4호
• /
• pp.318-323
• /
• 2015

For commercialization of fuel cell electric vehicles, one of the key objectives is to improve durability of MEA and electrocatalysts. Regarding electrocatalysts, the major issue is to reduce carbon corrosion and dissolution of Pt caused by harsh conditions, for example, SU/SD (Start-up/Shut-down). In this research, OER (Oxygen Evolution Reaction) catalyst has been developed improvement of durability. A modified polyol process is developed by controlling the pH of the solvent to synthesize the PtIr nanocatalysts on carbon supports. Each performance of the MEAs applying PtIr and Pt are equivalent because PtIrnanocatalysts have both ORR and OER activity. Breadboard test for catalyst durability in harsh conditions and high potentialsis found that the MEA applying PtIrnanocatalysts durability is improved more than the MEA applying Pt nanocatalysts.

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

• 한국재료학회지
• /
• 제32권5호
• /
• pp.237-242
• /
• 2022

Designing and producing a low-cost, high-current-density electrode with good electrocatalytic activity for the oxygen evolution reaction (OER) is still a major challenge for the industrial hydrogen energy economy. In this study, nanostructured Fe-doped CuCo(OH)₂ was discovered to be a precedent electrocatalyst for OER with low overpotential, low Tafel slope, good durability, and high electrochemically active surface sites at reduced mass loadings. Fe-doped CuCo(OH)₂ nanosheets are made using a hydrothermal synthesis process. These nanosheets are clumped together to form a highly open hierarchical structure. When used as an electrocatalyst, the Fe-doped CuCo(OH)₂ nanosheets required an overpotential of 260 mV to reach a current density of 50 mA cm^-2. Also, it showed a small Tafel slope of 72.9 mV dec^-1, and superior stability while catalyzing the generation of O₂ continuously for 20 hours. The Fe-doped CuCo(OH)₂ was found to have a large number of active sites which provide hierarchical and stable transfer routes for both electrolyte ions and electrons, resulting in exceptional OER performance.

• 한국표면공학회지
• /
• 제56권6호
• /
• pp.427-436
• /
• 2023

In the industry, it is recognized that human activities significantly lead to a large amount of wastewater, mainly due to the increased use of water and energy. As a result, the growing field of wastewater resource technology is getting more attention. The common technology for hydrogen production, water electrolysis, requires purified water, leading to the need for desalination and reprocessing. However, producing hydrogen directly from wastewater could be a more cost-effective option compared to traditional methods. To achieve this, a series of first-principle computational simulations were conducted to assess how waste nutrient ions affect standard electrolysis catalysts. This study focused on understanding the adsorption mechanisms of byproducts related to the oxygen evolution reaction (OER) in anion exchange membrane (AEM) electrolysis, using Co₃O₄ as a typical non-precious metal catalyst. At the same time, efforts were made to develop a comprehensive free energy prediction model for more accurate predictions of OER results.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2017년도 춘계학술대회 논문집
• /
• pp.168.1-168.1
• /
• 2017

화석연료를 대체하기 위한 에너지원으로서 수소에너지에 대한 연구가 활발히 진행되고 있다. 수전해는 무한 청정한 물을 전기분해하여 수소를 생산하는 기술로써 대표적으로 알칼리 수전해(alkaline water electrolysis, AWE)와 고분자 전해질막 수전해(polymer electrolyte membrane water electrolysis, PEMWE)가 있다. 그 중, AWE는 알칼리 분위기에서 물분해 반응이 진행되어 촉매의 부식 위험성이 비교적 낮기 때문에 상대적으로 저렴한 비귀금속 산화물 촉매를 사용할 수 있다는 장점이 있다. 본 연구에서는 비귀금속인 Cu, Co를 이용하여 $CuCoO_4$를 합성한 후 산소 발생 촉매 물질로 활용하여 산소 발생 반응(Oxygen Evolution Reaction, OER)특성을 고찰하였다.

• Journal of Electrochemical Science and Technology
• /
• 제6권4호
• /
• pp.121-130
• /
• 2015

The micro emulsion method has been successfully used for preparing perovskite LaCoO₃ with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO₃ powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO₃ and LaCoO₃-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO₃-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO₃. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO₃ layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO₃-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.