• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.47-50
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• 2008

The diastereoselectivity of Diels-Alder reactions were studied on the silica surface supported with different concentrations of cerium ion as efficient Lewis acid catalysts under solvent-free conditions. The results showed that the diastereoselectivity of reaction was highly improved in these conditions. The cerium ion was grafted on silica surface by using ion exchange method.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.26-26
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• 2007

To attest zinc electrodeposition mechanism, electric circuit models for zinc electro reaction on Pt electrode are analyzed from the a.c. impedance data. Electrochemical reactions of zinc deposition are composed of the three electrochemical reactions on the cathode layer and of the induced electrode layers.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1061-1066
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• 2014

Time-dependent formulations of the reactive scattering theory based on the wavepacket correlation functions with the M${\phi}$ller wavepackets for the electronically nonadiabatic reactions are presented. The calculations of state-to-state reactive probabilities for the quasi-Jahn-Teller scattering model system were performed. The conical intersection (CI) effects are investigated by comparing the results of the two-surface nonadiabatic calculations and the single surface adiabatic approximation. It was found that the results of the two-surface nonadiabatic calculations show interesting features in the reaction probability due to the conical intersection. Single surface adiabatic calculations with extended Born-Oppenheimer approximation using simple wavepacket phase factor was found to be able to reproduce the CI effect semi-quantitatively, while the single surface calculations with the usual adiabatic approximation cannot describe the scattering process for the Jahn-Teller model correctly.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.64-64
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• 2010

Ice film surfaces were examined by using the reactive ion scattering (RIS) of low energy (<35 eV) cesium ion beams. Neutral molecules (X) on the surface were detected in the form of cesium-molecule ion clusters (CsX+). Ionic species on the surface were desorbed from the surface via a low energy sputtering (LES) process below the threshold energy of secondary ion emission. The RIS and LES methods allowed us to study the H/D exchange reactions between H2O and D2O molecules on the surface and the associated proton transfer mechanisms. Specifically, H/D exchange kinetics was examined for D2O ice films (~10 BL) covered with a small amount of H2O (<0.5 BL), in the presence or absence of HCl adsorbates which provided excess protons on the surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.87-87
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• 2010

Adsorption and subsequent catalytic reactions of ethanol and acetaldehyde on chemically modified rutile TiO2(001) surfaces are probed by x-ray photoemission spectroscopy (XPS) using synchrotron radiation. TiO2 is a well-known photocatalyst for various catalytic reactions including oxidation of organic molecules. In this respect, the surface atomic structure has been found to play a vital role in determining the catalytic reactivity and selectivity of TiO2. In this study, we employ an atomically well-ordered reduced TiO2(001) surface which is prepared in a UHV chamber by repeated Ar+-sputtering and annealing (900 K) cycles. We systematically modify the surface by treating the surface with H2O or O2 at room temperature (RT). The catalytic reactivity of the surface-modified TiO2(001) is evaluated by dosing ethanol/acetaldehyde onto the surface at RT and by subsequent annealing to higher temperatures (400~600 K). XPS spectra of C 1s core level are intensively used to probe any change in the oxidation state of carbon atoms. We find that the reactivity as well as the saturation coverage are significantly affected by the RT-treatment of the TiO2 surface with H2O or O2. For both reactant molecules (ethanol/acetaldehyde), oxidation reactions are found to be enhanced on the O2-treated surface compared with the reduced or H2O-treated surfaces. Possibly reaction pathways are discussed based on the observed XPS spectra.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.481-484
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• 2003

Sulfide minerals contacted with air and water in coal seam cause oxidation reactions. This oxidation reactions make low pH of groundwater and surface water(Acid Drainage). The reddish brown precipitate collected from the cut slope of the study area was estimated using the X-Ray Diffractometer(XRD). XRD results show that the cut slope was affected by Acid Drainage. The cut slope exposured to Acid Drainage become weak about chemical weathering and defile the appearance of the road. Drainage facilities are very important in Cut Slope under Acid Drainage influence. Reactions between Coal seam and water cause chemical weathering and environmental problem. Therefore It is important to control the transfer paths of groundwater and surface water and to install water collecting facilities

• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1323-1327
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• 2001

The catalyst Ni/MgO (Ni : 15 wt%) has been applied to methane reforming reactions, such as steam reforming of methane (SRM), partial oxidation of methane (POM), and oxy-steam reforming of methane (OSRM). It showed high activity and good stability in all the reforming reactions. Especially, it exhibited stable catalytic performance even in stoichiometric SRM (H2O/CH4 = 1). From TPR and H2 pulse chemisorption results, a strong interaction between NiO and MgO results in a high dispersion of Ni crystallite. Pulse reaction results revealed that both CH4 and O2 are activated on the surface of metallic Ni over the catalyst, and then surface carbon species react with adsorbed oxygen to produce CO.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.128.1-128.1
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• 2013

We investigated the correlation between electrical transport and mechanical stress in $Bi_2Te_2Se$ by using a conductive probe atomic force microscopy in an ultra-high vacuum environment. Uniform distribution of measured friction and current were observed over a single quintuple layer terrace, which is an indication of the uniform chemical composition of the surface. By measuring the charge transport of $Bi_2Te_2Se$ surface as a function of the load applied by a tip to the sample, we found that the current density varies with applied load. The variation of current density was explained in light of the combined effect of the changes in the in-plane conductance and spin-orbit coupling that were theoretically predicted. We suppose that the local density of states is modified by tip-induced strain, but topological phase still remains. We exposed a clean topological insulator surface by tip-induced indentation. The surface conductance on the indented $Bi_2Te_2Se$ surface was studied, and the role of surface oxide on the surface conductance is discussed.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.4
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• pp.451-465
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• 2003

The major conversion processes of SO$_2$ to sulfate are reactions in gaseous, aqueous phase and on dust surface. Using the measurement data in Ganghwa, the background area of metropolitan Seoul Area, the relative contiribution of the conversion processes are estimated. Generally, aqueous cloud if the most important conversion path followed by dust surface, gas, and aqueous aerosol. Importance of conversion on dust surface increases for the dust storm period. The total conversion rate values over the metropolitan Seoul area are between 1.5 and 8.8$\times$10$^{-11}$ mole m$^{-3}$ air.

• Journal of the Korean institute of surface engineering
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• v.50 no.1
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• pp.1-9
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• 2017

Design of novel materials in renewable energy systems plays a key role in powering transportation vehicles and portable electronics. This review introduces the research work of first principles-based computational design for the materials over the last decade to accomplish the goal with less financial and temporal cost beyond the conventional approach, especially, focusing on electrocatalyst toward a proton exchange membrane fuel cell (PEMFC). It is proposed that the new method combined with experimental validation, can provide fundamental descriptors and mechanical understanding for optimal efficiency control of a whole system. Advancing these methods can even realize a computational platform of the materials genome, which can substantially reduce the time period from discovery to commercialization into markets of new materials.