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719 results on '"Kim, Ji Man"'

151. Catalytic Properties of Nanoporous Manganese Oxides in Decomposition of High-Purity Hydrogen Peroxide

Author

Lee Choul‐Ho, Jeon Jong‐Ki, Jeong Byung‐Hun, Kim Goun, Han Jeongsik, and Kim Ji Man

Subjects
Materials science, Nanoporous, Inorganic chemistry, Biomedical Engineering, chemistry.chemical_element, Bioengineering, 02 engineering and technology, General Chemistry, Manganese, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Decomposition, 0104 chemical sciences, Catalysis, chemistry.chemical_compound, chemistry, General Materials Science, 0210 nano-technology, Hydrogen peroxide
Published
2016

159. Pd/SiO2 as an active and durable CH4 oxidation catalyst for vehicle applications.

Author

Oh, Dong Gun, Lee, Jaekyoung, Kim, Eunseok, Jang, Eun Jeong, Kim, Ji Man, and Kwak, Ja Hun

Subjects
SCANNING transmission electron microscopy, PALLADIUM catalysts, NATURAL gas vehicles, FOURIER transform infrared spectroscopy, CATALYST poisoning, DETERIORATION of materials, OXIDATION
Abstract

[Display omitted] • Fresh prepared Pd/SiO 2 shows superior CH 4 oxidation activity than Pd/Al 2 O 3. • Pd/SiO 2 shows serious deactivation after hydrothermal aging. • Deactivated Pd/SiO 2 catalysts can completely regenerate by H 2 reduction treatment. The removal of CH 4 is critical to address environmental concerns for developing natural gas vehicles (NGVs), because CH 4 has a 20-fold-greater contribution to the greenhouse effect than CO 2. Alumina supported Pd catalysts are widely used for CH 4 oxidation due to their superior catalytic activity and durability compared to other CH 4 oxidation catalysts. However, the continuous deactivation of Pd-based catalysts during vehicle applications needs further development of active and durable catalysts. Here, we report that Pd/SiO 2 can be active and durable catalysts for CH 4 oxidation in practically relevant condition via a simple reductive regeneration. CH 4 oxidation light-off curves of freshly prepared Pd/SiO 2 (air, 550 °C) present higher activity than those of Pd/Al 2 O 3 , but severe deactivation was observed after hydrothermal aging (HTA, air with 10% H 2 O) at 850 °C. However, X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and volumetric CO adsorption suggest that Pd/SiO 2 has similar particle sizes as Pd/Al 2 O 3 even after HTA, indicating that Pd/PdO particle sintering is not the origin of the deactivation of Pd/SiO 2. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows that the CO was not adsorbed on Pd/SiO 2 after HTA, whereas it was adsorbed on Pd/Al 2 O 3 after HTA. These results demonstrate that the deactivation of Pd/SiO 2 originates mainly from the blockage of the Pd/PdO surface by the SiO 2 overlayer formed during HTA. The Pd/PdO surfaces are re-exposed by a simple H 2 treatment at 500 °C, resulting in CO adsorption on the Pd/PdO surface and regeneration for CH 4 oxidation activity, which suggests that the Pd/PdO surface was re-exposed by a reduction treatment. This work also demonstrates that SiO 2 -supported Pd catalysts can be a good candidate for active and durable CH 4 oxidation catalysts by using the proper regeneration protocols. [ABSTRACT FROM AUTHOR]

Published
2021
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161. Raman scattering of true 1D van der Waals Nb2Se9 nanowires.

Author

Lee, Junho, Kim, Bum Jun, Chung, You Kyoung, Lee, Weon‐Gyu, Choi, Ik Jun, Chae, Sudong, Oh, Seungbae, Kim, Ji Man, Choi, Jae‐Young, and Huh, Joonsuk

Subjects
RAMAN scattering, RAMAN spectroscopy, DENSITY functional theory, NANOWIRES, SPECTRUM analysis
Abstract

In the present study, the experimental Raman spectrum of niobium‐selenide nanowires (Nb2Se9) is reported for the first time followed by an analysis of the Raman spectrum using the density functional theory (DFT). According to the group‐theoretical analysis, 33 Ag modes were identified as Raman active modes. In the experimental spectrum, 19 well‐resolved Raman modes were observed: 13 modes in the low‐wavenumber range (50–200 cm−1) and six modes in the high‐wavenumber range (220–340 cm−1). The DFT calculations were performed using the local‐density approximation (LDA) functional and generalized gradient approximation (GGA) functional of Perdew–Burke–Ernzerhof (PBE) with van der Waals corrections (PBE‐D3). PBE‐D3 showed better compatibility with the experimental data for the high‐wavenumber range. Our results provide an essential reference for the Raman scattering of newly synthesized Nb2Se9 nanowires and nanodevices in the future. [ABSTRACT FROM AUTHOR]

Published
2020
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166. Exceptional Lithium Storage in a Co(OH)2 Anode: Hydride Formation

Author

Kim, Hyunchul, primary, Choi, Woon Ih, additional, Jang, Yoonjung, additional, Balasubramanian, Mahalingam, additional, Lee, Wontae, additional, Park, Gwi Ok, additional, Park, Su Bin, additional, Yoo, Jaeseung, additional, Hong, Jin Seok, additional, Choi, Youn-Suk, additional, Lee, Hyo Sug, additional, Bae, In Tae, additional, Kim, Ji Man, additional, and Yoon, Won-Sub, additional

Published
2018
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183. Highly stable mesoporous metal oxides using nano-propping hybrid Gemini surfactants

Author

Yi-Yeol Lyu, Seung Hwan Yi, Jeong Kuk Shon, Chang, Seok, Lyong Sun Pu, Jae Eui Yie, Sang-Yun Lee, Char, Kookheon, Stucky, Galen D., and Kim, Ji Man

Subjects
Surface active agents -- Usage, Silicon compounds -- Analysis, Silicon compounds -- Chemical properties, Siloxanes -- Analysis, Siloxanes -- Chemical properties, Chemistry
Abstract

A new type of Gemini surfactant containing a siloxane moiety, which can yield highly stable mesoporous metal oxides after the removal of the surfactant via the nano-propping pathway, is described. Structures of the Gemini surfactant and a schematic diagram for the nano-propping pathway are presented.

Published
2004

194. Lithium-Ion Batteries: Discovering a Dual-Buffer Effect for Lithium Storage: Durable Nanostructured Ordered Mesoporous Co-Sn Intermetallic Electrodes (Adv. Funct. Mater. 17/2016)

Author

Park, Gwi Ok, primary, Yoon, Jeongbae, additional, Shon, Jeong Kuk, additional, Choi, Yun Seok, additional, Won, Jong Gu, additional, Park, Su Bin, additional, Kim, Kyoung Ho, additional, Kim, Hansu, additional, Yoon, Won-Sub, additional, and Kim, Ji Man, additional

Published
2016
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