• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.539-548
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• 2016

The non-noble 1D nanofibers(NFs) prepared by electrospinning and calcination method were used as oxygen evolution reaction (OER) electrocatalyst for water electrolysis. The electrospinning process and rate of solution composition was optimized to prepare uniform and non-beaded PVP polymer electrospun NFs. The diameter and morphology of PVP NFs changed in accordance with the viscosity and ion conductivity. The clean metal precursor contained electrospun fibers were synthesized via the optimized electrospinning process and solution composition. The calcined $CuCo_2O_4$ NFs catalyst showed higher activity and long-term cycle stability for OER compared with other $Co_3O_4$, $NiCo_2O$ NF catalysts. Furthermore, the $CuCo_2O_4$ NFs maintained the OER activity during long-term cycle test compared with commercial $CuCo_2O_4$ nanoparticle catalyst due to unique physicochemical and electrochemical properties by1D nanostructure.

• Journal of Electrochemical Science and Technology
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• v.14 no.1
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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.

• Journal of the Korean Electrochemical Society
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• v.13 no.1
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• pp.45-49
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• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.471-477
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• 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 $IrO_2$.

• Korean Journal of Materials Research
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• v.28 no.7
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• pp.428-434
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• 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.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.280-288
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• 1996

In the ozone evolution using $PbO_2$, which was electrodeposited on Ti plate at various conditions in electrolyte, the effects of lead dioxide structure on the current efficiency and surface structure changes of lead dioxide were investigated. Also the effects of oxygen transfer reaction on the ozone evolution were investigated by means of a $PbO_2$ electrodeposited on the platinum rotating disk electrode. In order to develope an electrode for ozone evolution, durability of lead dioxide and optimum current density were investigated. At the electrodeposited lead dioxide with the larger grain size and higher crystallinity, the efficiency for ozone evolution was higher. Optimum current density to electrodeposite lead dioxide with large grain size and high crystalinity was $50mA/cm^2$. Lead dioxide deposited in the presence of glycerin showed the best advantage of ozone evolution. Also lead dioxide electrodeposited at less than $10mA/cm^2$ or at more than $100mA/cm^2$ has poor performance of ozone evolution and poor adhesive strength to substrate. In the beginning of ozone evolution, surface structure of lead dioxide was changed and this change resulted in good effects on ozone evolution. Lead dioxide doped with other elements was favorable not to ozone evolution but to oxygen evolution, so it is speculated that ozone evolution has not intermediate stage of oxygen evolution and occurs competitively with oxygen evolution. When ozone was evolved at $0.7{\sim}0.8A/cm^2$, the current efficiency was highest.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.318-323
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• 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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.3
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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.

• Korean Journal of Materials Research
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• v.32 no.5
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• pp.237-242
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• 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.

• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.427-436
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• 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.