• Journal of Hydrogen and New Energy
• /
• v.18 no.4
• /
• pp.356-364
• /
• 2007

The partial reduction and water splitting properties of metal substituted ferrite mediums for two-step thermochemical hydrogen production, were carried out by TPR/O(Temperature programmed reduction/oxidation) method at a temperature of below 1173 K and under atmospheric pressure. $ZrO_2$ was added to the ferrite as a binder to prevent the sintering. As the results, the reactivity of the metal species added to the ferrite mediums decreased in the order of Cu>Co>Ni>Mn, on the basis of water-splitting temperature. It was also found that the produced hydrogen amounts in the water-splitting step on partial reduced mediums were corresponding to the consumed hydrogen amounts in the previously partial reduction step.

• Journal of Hydrogen and New Energy
• /
• v.34 no.2
• /
• pp.132-140
• /
• 2023

In this study, rotary magnet holder (RMH) was manufactured to analyze the ion transport effect according to the rotating magnetic field for the hydrogen production efficiency by alkaline water electrolyte. In the experiment, the voltage signal according to the magnet arrangement inside the RMH, the rotation speed, and the rotation time was measured using the voltage measurement module. As a result of the voltage signal measurement experiment, the average potential difference increased as the rotation speed of the RMH increased. Through the results of the voltage signal measurement experiment, the most efficient magnet arrangement (case 2) was applied to the RMH to conduct a water electrolysis experiment. A 20% NaOH aqueous solution was filled in the electrolytic cell, and a direct current 2 V constant voltage was applied to measure the current value according to the RMH rotation to compare the hydrogen generation amount. When rotating at 100 RPM, the hydrogen production efficiency increased by 8.06% compared to when not rotating. Considering the area exceeding +25 mA, which was not measured at the beginning of the experiment, an increase in hydrogen production of about 10% or more can be expected.

• Journal of Hydrogen and New Energy
• /
• v.35 no.2
• /
• pp.162-167
• /
• 2024

Fossil fuels have been main energy source to people. However, enormous amount of CO₂ was emitted over the world , resulting in global climate crisis today. Recently, solid oxide electrolyzer cell (SOEC) is getting attention as an effective way for producing H₂, a clean energy resource for the future. Also, SOEC could be applicable to reverse water-gas shift reaction process due to its high-temperature operating condition. Here, SOEC system was utilized for both H₂ production and CO₂ reduction process, allowing product gas composition change by controlling operating conditions.

• Journal of Hydrogen and New Energy
• /
• v.15 no.1
• /
• pp.23-31
• /
• 2004

For the fabrication of high efficient bifunctional electrocatalyst of oxygen electrode for PEM URFC (Polymer Electrolyte Membrane Unitized Regenerative Fuel Cell), which is a promising energy storage and conversion system using hydrogen as the energy medium, several bifunctional electrocatalysts were prepared and tested in a single cell URFC system. The catalysts for oxygen electrode revealed fuel cell performance in the order of Pt black > PtIr > PtRuOx > PtRu ~ PtRuIr > PtIrOx, whereas water electrolysis performance in the order of PtIr ~ PtIrOx > PtRu > PtRuIr > PtRuOx ~ Pt black. Considering both reaction modes PtIr was the most effective elctrocatalyst for oxygen electrode of present PEM URFC system. In addition, the water electrolysis performance was significantly improved when Ir or IrOx was added to Pt black just 1 wt.% without the decrease of fuel cell performance. Based on the catalyst screening and the optimization of catalyst composition and loading, the optimum catalyst electrodes for PEM URFC were $1.0mg/cm^2$ of Pt black as hydrogen electrode and $2.0mg/cm^2$ of PtIr (99:1) as oxygen electrode.

• Journal of Hydrogen and New Energy
• /
• v.15 no.3
• /
• pp.201-207
• /
• 2004

Redox characteristics of metal oxide for hydrogen production by thermochemical water-splitting were investigated. $CuFe_2O_4$ as a redox pair that had a different molar ratio of Cu and Fe were prepared by co-precipitation method. Hydrogen production consisted of water-splitting step and thermal reduction step was performed below 1200K. Redox characteristics of Cu-ferrites were studied using the thermal gravimetric analysis technique. Also, structure change of Cu-ferrite during thermal reduction was investigated using the high temperature controlled XRD. In results, oxygen release of Cu-ferrite during the thermal reduction was initiated at oxygen site combined with Cu. Consequently, oxygen release amount of Cu-ferrite was increased with increase of Cu molar ratio of Cu-ferrite. It was found that thermal reduction of Cu-ferrite was begun at $875^\circ{C}$. It was confirmed that structure of Cu-ferrite was changed to metal and cation excess metal oxide during the thermal reduction step.

• Korean Chemical Engineering Research
• /
• v.49 no.6
• /
• pp.688-696
• /
• 2011

Hydrogen is one of the few long-term sustainable clean energy carriers, emitting only water as by-products during its combustion or oxidation. The use of fossil fuels to produce hydrogen makes large amount of carbon dioxide (>7 kg $CO_{2}$/kg $H_{2}$) during the reforming processes. Hydrogen production can be environmentally benign only if the energy and the resource to make hydrogen is sustainable and renewable. Biomass is an attractive alternative to fossil fuels for carbon dioxide because of the hydrogen can be produced by conversion of the biomass and the carbon dioxide formed during hydrogen production is consumed by biomass generation process. Hydrogen production using solar energy also attracts great attention because of the potential to use abundance natural energy and water.

• Journal of Powder Materials
• /
• v.31 no.2
• /
• pp.163-168
• /
• 2024

As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 ℃ and hydrogen partial pressure above 0.5 atm, Ni and Li₂O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H₂O, and Li₂CO₃, with about 0.02 wt% Al as an impurity.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.26 no.3
• /
• pp.301-305
• /
• 2012

The purpose of this study is to investigate effects of Anisi stellati Fructus Water Extract on hydrogen peroxide production in RAW 264.7 mouse macrophages. Anisi stellati Fructus were extracted by hot water. Effects of Anisi stellati Fructus water extract (AS) on hydrogen peroxide production in RAW 264.7 were measured by dihydrorhodamine 123 assay after 20, 24, 28, 44, 48, and 52 h incubation at the concentrations of 10, 25, 50, and $100{\mu}g/mL$. For 20 h incubation, AS significantly increased hydrogen peroxide production in RAW 264.7 cells by $108.6{\pm}1.56%$, $109.5{\pm}1.94%$, $108.4{\pm}1.14%$, and $107.3{\pm}3.06%$ at the concentrations of 10, 25, 50, and $100{\mu}g/mL$ (P < 0.05) respectively. For 24, 28, 44, 48, and 52 h incubation, AS also significantly increased hydrogen peroxide production in RAW 264.7 cells at the concentrations of 10, 25, 50, and $100{\mu}g/mL$ (P < 0.05). These results suggest that Anisi stellati Fructus has the immune - enhancing property related with its increase of hydrogen peroxide production in macrophages.

• Journal of Hydrogen and New Energy
• /
• v.19 no.4
• /
• pp.305-312
• /
• 2008

ZnO/Zn redox cycle is the one of the promising thermochemical cycles for hydrogen production via water splitting with high temperature heat source like a concentrated solar energy. This paper reports the particle size effect of Zinc on water splitting behavior. Water splitting reaction experiments were carried out at isothermal conditions of 350 and 400$^{\circ}C$ in TGA (Thermo Gravimetric Analyzer) using four commercial Zinc powders (nano, <10 ${\mu}m$, <150 ${\mu}m$ and $150{\sim}600\;{\mu}m$ particle sizes). Before the experiments, average particle size of Zinc powders was analyzed by PSA (Particle Size Analysis). After the experiments, XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscope) analyses were conducted on the samples. The experimental results showed that particle size had a effect on the conversion of Zinc to ZnO. Zinc conversion was increased, as the particle size decreased. Especially, the nano size particles were aggregated and the particle's morphology changed on the surface during hydrolysis reaction.

• Journal of the Korean Institute of Gas
• /
• v.28 no.1
• /
• pp.65-72
• /
• 2024

Green Hydrogen demonstration complex is under conduction in Jeju island which is rich in renewable energy resources and will produces green hydrogen using a water electrolysis systems. In order to check durability of long-term operation, AST(accelerated stress test) was applied and the power pattern based on Jeju Island's wind power was applied. After 800 hours of repeated application of low current and high current, the performance of the PEM water electrolysis cell was reduced by up to 10% and by about 5.5% in operating conditions. As the result of impedance analysis, it can be seen that the electrode polarization resistance greatly increased than ohmic polarization resistance. In addition, when the durability evaluation was conducted by applying the wind power pattern of Jeju Island, the performance of the PEM water electrolysis cell showed up to 1.6% and a decrease of less than 1% in operating conditions. As a result of the impedance, it can be seen that the change of ohmic resistance and electrode polarization resistance is small.