• Journal of Hydrogen and New Energy
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• v.27 no.3
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• pp.276-282
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• 2016

The effects of conductive additives in a $La_{0.8}Sr_{0.2}MnO_3$ perovskite bifunctional electrode for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated in an alkaline solution. Highly porous carbon black (CB) and Ni powder were added to the bifunctional electrodes as conductive additives. The surface morphologies of electrodes containing CB and Ni were observed by scanning electron microscopy (SEM). The current densities for both ORR and OER were changed by the addition of CB. The conductive additive changed physical properties of bifunctional electrodes such as the sheet conductance, gas permeability and contact angle. It was observed that the air permeability of electrode was most effective to enhance the currents for ORR and OER.

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1047-1053
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• 2009

The future use of hydrogen as an energy source is expected to increase on account of its environmentally friendliness. In order to enhance the production of hydrogen, Pd ions (0.01, 0.05, 0.1, and 0.5 mol%) were incorporated $TiO_2$ (Pd-$TiO_2$) and used as a photocatalyst. The UV-visible absorbance decreased with increasing level of palladium incorporation without a wavelength shift. Although all the absorption plots showed excitation characteristics, there was an asymmetric tail observed towards a higher wavelength caused by scattering. However, the intensity of the photoluminescence (PL) curves of Pd-$TiO_2$ was smaller, with the smallest case being observed at 0.1 and 0.5 mol% Pd-$TiO_2$, which was attributedto recombination between the excited electrons and holes. Based on these optical characteristics, the evolution of $H_2$ from methanol/water (1:1) photo-splitting over Pd-$TiO_2$ in the liquid system was enhanced, compared with that over pure $TiO_2$. In particular, 2.4 mL of $H_2$ gas was produced after 8 h when 0.5 g of a 1.0 mol% Pd-$TiO_2$ catalyst was used. $H_2$ was stably evolved even after 28 h without catalytic deactivation, and the amount of $H_2$ produced reached 14.5 mL after 28 h. This is in contrast to the case of the Pd 0.1 mol% impregnated $TiO_2$ of $H_2$ evolution of 17.5 mL due to the more decreasedelectron-hole recombination.

• Journal of Electrochemical Science and Technology
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• v.10 no.4
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• pp.402-407
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• 2019

Water electrolysis is known as the most sustainable and clean technology to produce hydrogen gas, however, a serious drawback to commercialize this technology is due to the slow kinetics in oxygen evolution reaction (OER). Thus, we report on the nanoporous IrNi thin film that reveals a markedly enhanced OER activity, which is attained through a selective etching of Os from the IrNiOs alloy thin film. Interestingly, electrochemical selective etching of Os leads to the formation of 3-dimensionally interconnected nanoporous structure providing a high electrochemical surface area (ECSA, 80.8 ㎠), which is 90 fold higher than a bulk Ir surface (0.9 ㎠). The overpotential at the nanoporous IrNi electrode is markedly lowered to be 289 mV at 10 mA cm^-2, compared with bulk Ir (375 mV at 10 mA cm^-2). The nanoporous IrNi prepared through the selective de-alloying of Os is promising as the anode material for a water electrolyzer.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.272-272
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• 2013

The attractive features of photosynthetic reaction center proteins for energy application make them useful in solar energy conversion to hydrogen fuel or electrical energy. Almost unity charge separation quantum yield and its rapid speed of ~1ns, absorbance region in visible light (480~740 nm) and high proportion of photosynthetically active solar energy of 48.5% allowed photosystem1 to exploited as a bio-material for photo-energy devices. Directionality of photosystem1 in electron transfer can solve main problem in two-step water splitting process where back reaction deteriorates the overall efficiency. In the study, photosystem1 was extracted from spinach and the photo-induced excited electron in the reaction center was utilized in various field of light energy application. First, hydrogen evolving system realized by photodeposition of platinum at the end of the electron transfer chain, with combining specific semiconductor to oxidize water in the first step of Z-scheme. The evaluation by gas-chromatography demonstrated hydrogen evolution through the system. For the further application of photoelectrical material on electrode, photosystem1 have been controlled by copper ion, which is expected to assemble photosystem in specific orientation followed by maximized photoelectrical ability of film. The research proposed concrete methods for combining natural protein and artificial materials in one system and suggested possibility of designing interface between biological and inorganic materials.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.41.1-41.1
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• 2012

Interactions between the galactic interstellar medium (ISM) and the intra cluster medium (ICM) are believed to be one of the main processes affecting galaxy evolution in cluster environments. The aim of our research is to study the molecular gas properties of a galaxy under the ICM pressure in the cluster environment. It has been well known that cluster galaxies are deficient in atomic hydrogen gas (HI gas) compared to their field counterparts and now there is much evidence that low density ISM is being removed by ram pressure due to ICM wind. Meanwhile, no significant molecular gas deficiency of the cluster galaxy population has been found yet they show overall lower star formation rate than galaxies in the field, and it is still puzzling how the star formation could decrease without stripping of dense molecular gas. To address this issue, we probe the detailed molecular gas properties of NGC 4402, located near the cluster center, as part of a study of four spiral galaxies in the Virgo Cluster. NGC 4402 is well known undergoing ram pressure stripping with a truncated HI disk($D_{HI}/D_{opt}$ - 0.75 and only 36% of HI gas compare to field galaxies of a similar size) and a disturbed gas morphology. Comparing the high resolution 12CO and 13CO data of NGC 4402 from the Sub Millimeter Array (SMA) with existing other wavelength data, we probe the spatial distribution and a physical condition of molecular gas under strong ICM pressure. We discuss the star formation activity might have been altered and hence how the global color of NGC4402 would change in the future.

• Resources Recycling
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• v.20 no.4
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• pp.71-77
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• 2011

$MoO_3$ powders were reduced to $MoO_2$ under Ar+$H_2$ gas mixture in a tubular furnace at temperature range 723~873 K. Reaction rate was quantitatively deduced by measuring relative humidity of off gas. Observed reaction rate increased significantly with hydrogen partial pressure and reaction temperature and the rate of $H_2O$ evolution increased drastically during the initial period of reduction. As reduction proceeded, however, $H_2O$ partial pressure decreased noticeably. During the initial period of the reduction, a linear relationship for time dependence of the reduction fraction was observed. The activation energy for the reduction of $MoO_3$ to $MoO_2$was 73.56 kJ/mol during the initial period of reduction.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2073-2080
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• 2013

In this study the effects of adding alkaline-earth (IIA) metal oxides to NiZr-loaded Zeolite Y catalysts were investigated on hydrogen rich production by ethanol steam reforming (ESR). Four kinds of alkaline-earth metal (Mg, Ca, Sr, or Ba) oxides of 3.0% by weight were loaded between the $Ni_6Zr_4O_{14}$ main catalytic species and the microporous Zeolite Y support. The characterizations of these catalysts were examined by XRD, TEM, $H_2$-TPR, $NH_3$-TPD, and XPS. Catalytic performances during ESR were found to depend on the basicity of the added alkaline-earth metal oxides and $H_2$ production and ethanol conversion were maximized to 82% and 98% respectively in 27($Ni_6Zr_4O_{14}$)3MgO/70Zeolite Y catalyst at $600^{\circ}C$. Many carbon deposits and carbon nano fibers were seen on the surface of $30Ni_6Zr_4O_{14}$/70Zeolite Y catalyst but lesser amounts were observed on alkaline-earth metal oxide-loaded 27($Ni_6Zr_4O_{14}$)3MO/70Zeolite Y catalysts in TEM photos after ESR. This study demonstrates that hydrogen yields from ESR are closely related to the acidities of catalysts and that alkaline-earth metal oxides reduce the acidities of 27($Ni_6Zr_4O_{14}$)3MO/70Zeolite Y catalysts and promote hydrogen evolution by preventing progression to hydrocarbons.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.611-623
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• 2024

The ISP-47 TOSQAN experiment was analyzed with containmentFOAM which is an open-source CFD code based on OpenFOAM. The containment phenomena taking place during the experiment are gas mixing, stratification and wall condensation in a mixture composed of steam and non-condensable gas. The k-ω SST turbulence model was adopted with buoyancy turbulence models. The wall condensation model used is based on the diffusion layer approach. We have simulated the full TOSQAN experiment which had a duration 20000 s. Sensitivity studies were conducted for the buoyancy turbulence models with SGDH and GGDH and there were not significant differences. All the main features of the experiments namely pressure history, temperature, velocity and gas species evolution were well predicted by containemntFOAM. The simulation results confirmed the formation of two large flow stream circulations and a mixing zone resulting by the combined effects of the condensation flow and natural convection flow. It was found that the natural convection in lower region of the vessel devotes to maintain two large circulations and to be varied the height of the mixing zone as result of sensitivity analysis of non-condensing wall temperature. The computational results obtained with the 2D mesh grid approach were comparable to the experimental results.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.289-296
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• 2008

Electrochemical studies were performed by a half-cell test for the nickel hydroxide (cathode) and hydrogen storage alloy(anode) electrodes for the sealed Ni-MH batteries applicable to industrial use. The electrodes were fabricated and checked a charge efficiency and an internal pressure of the battery during charge-discharge cycling. In order to reduce the internal pressure of the sealed Ni-MH battery, cyclic voltammetry (CV) were performed on the electrodes of nickel hydroxide(cathode) and hydrogen storage alloy(anode), respectively. The results of the test showed clearly the oxidation/reduction and oxygen evolution reaction in a nickel hydroxide electrode and the hydrogenation behavior of a hydrogen storage electrode. The sealed Ni-MH battery of 130Ah was fabricated by using nickel hydroxide of a high over-voltage for an oxygen gas evolution and hydrogen storage alloy of a good performance for activation The battery showed a good characteristics such as a high charge efficiency of 98% at 1 C charge current, a low level internal pressure of 4 atm on a continuous over-charging and a large preservation capacity of 95% at 400 cycle.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.302-308
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• 2009

This study investigated the production of hydrogen over Ga (1.0, 2.0, and 5.0 mol%)-$TiO_2$ photocatalysts prepared by a solvothermal method. The absorption band was slightly blue-shifted upon the incorporation of the gallium ions, but the intensity of the photoluminescence (PL) curves of Ga-incorporated $TiO_2$s was distinguishably smaller, with the smallest case being the 2.0 mol% Ga-$TiO_2$, which was related to the recombination between the excited electrons and holes. $H_2$ evolution from photo splitting of water over Ga-incorporated $TiO_2$ in the liquid system was enhanced, compared to that over pure $TiO_2$; particularly, the production of 5.6 mL of $H_2$ gas after 8 h when 1.5 g of the 2.0 mol% Ga-incorporated $TiO_2$ was used.