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623 results on '"Kim, Seung Hoon"'

109. Impact of the dopant-induced ensemble structure of hetero-double atom catalysts in electrochemical NH3 production.

Author

Kim, Seung-hoon, Song, Ho Chang, Yoo, Sung Jong, Han, Jonghee, Lee, Kwan-Young, and Ham, Hyung Chul

Abstract

Using spin-polarized density functional theory (DFT) calculations, we examined electrochemical N2 reduction (N2RR) toward NH3 production on hetero-RuM (M = 3d transition metals) double atom catalysts supported on defective graphene by means of analysis on the geometric ensemble structure, the N2RR mechanism, the decoupling of strain, dopant and configurational effects and the d-orbital resolved density of states (ORDOS) (dz2, dxz, dyz, dxy, and dx2–y2) on the hetero-double atoms. In addition, we computationally screened novel catalysts by exploring 4d, 5d and p block metals as the hetero-M metals in the RuM system. First, we found the significantly enhanced N2RR activity of inclined pentagon M (Fe, Mn, and Sc) double atom catalysts (RuFe has the highest activity) compared to the homo-Ru2 double atom catalyst. Our DFT calculations on the interplay of strain, dopant and configurational effects in the inclined pentagon M (Fe, Mn, and Sc) double atom catalysts predicted that (1) the dopant effect was the promoter to improve the N2RR activity of RuSc and RuMn, (2) the tensile strain (RuSc) tended to reduce the NH3 productivity via the N2RR, while the effect of compressive strain (RuFe and RuMn) was insignificant, and (3) the dopant-support interaction induced a unique inclined pentagon M double atom ensemble structure, which leads to the large reduction of the N2RR activity of the hetero-RuSc double atom but the activity increases for the hetero-RuFe and RuMn cases. Finally, our DFT calculation on the analysis of the p–d (dz2, dxz, dyz, dxy, and dx2–y2) orbital overlap identified the key d orbitals in determining the descriptor (NH2 adsorption energy) for representing the N2RR. That is, the orbitals (dz2, dxz, and dyz) having an orientation toward the z direction in the horizontal Ru2 double atom played an important role in determining the NH2 adsorption process, while for the inclined pentagon M double atoms (RuFe, RuSc, and RuMn), the dxz and dxy orbitals were found to be essential for the modification of NH2 adsorption energy. Finally, a descriptor based DFT search additionally discovered promising hetero-RuOs and RuIr double atom catalysts. This study highlights that the dopant engineering of hetero-double atom catalysts supported on defective graphene can significantly modify the electrochemical reactivity, particularly by the dopant type and geometric ensemble structure. [ABSTRACT FROM AUTHOR]

Published
2022
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120. Porous Strained Pt Nanostructured Thin‐Film Electrocatalysts via Dealloying for PEM Fuel Cells

Author

Hwang, Chang‐Kyu, primary, Kim, Jong Min, additional, Hwang, Sehoon, additional, Kim, Joo‐Hyung, additional, Sung, Chang Hyun, additional, Moon, Byung‐Moo, additional, Chae, Keun Hwa, additional, Singh, Jitendra Pal, additional, Kim, Seung‐Hoon, additional, Jang, Seung Soon, additional, Lee, Seung Woo, additional, Ham, Hyung Chul, additional, Han, Seunghee, additional, and Kim, Jin Young, additional

Published
2019
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135. Electrocatalytic glycerol oxidation enabled by surface plasmon polariton-induced hot carriers in Kretschmann configuration

Author

Chung, Kyungwha, primary, Zhu, Xingzhong, additional, Zhuo, Xiaolu, additional, Jang, Yu Jin, additional, Choi, Chi Hun, additional, Lee, June Sang, additional, Kim, Seung-hoon, additional, Kim, Minju, additional, Kim, Kiheung, additional, Kim, Donghyun, additional, Ham, Hyung Chul, additional, Baba, Akira, additional, Wang, Jianfang, additional, and Kim, Dong Ha, additional

Published
2019
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137. Hydrogen production by steam reforming of biomass-derived glycerol over Ni-based catalysts

Author

Moon Dong Ju, Lee Kwan-Young, Yang Eun‐Hyeok, Jung Jae-Sun, and Kim Seung-hoon

Subjects
Thermogravimetric analysis, Hydrogen, Catalyst support, Inorganic chemistry, Industrial catalysts, chemistry.chemical_element, General Chemistry, Catalysis, law.invention, Steam reforming, chemistry, Chemical engineering, law, Calcination, Hydrogen production
Abstract

The steam reforming of bio-glycerol for the production of hydrogen has been investigated in a fixed-bed reactor containing spherical particle of Ni supported on γ-Al 2 O 3 as catalyst. Several catalysts were prepared by the dry impregnation method at different calcination temperatures (750–950 °C) with/without the addition of various alkaline promoters (K, Ca, Sr). The physical and chemical properties of the prepared catalysts were characterized by nitrogen (N 2 ) physisorption, X-ray diffraction (XRD), temperature-programmed reduction, thermogravimetric analysis, scanning electron microscopy-energy dispersive X-ray spectroscopy and transmission electron microscopy techniques. The Ni/γ-Al 2 O 3 catalysts showed a high glycerol conversion and hydrogen selectivity, however they gradually deactivated due to the formation of carbon over those catalysts. Nevertheless, it was found that the catalysts calcined at high temperatures could inhibit the formation of carbon without affecting the glycerol conversion and hydrogen selectivity. The addition of alkaline promoters caused a slight decrease in the glycerol conversion, but also reduced the formation of carbon and thereby increased the long-term stability of the catalyst.

Published
2014

139. Design and Fabrication of CNT-Based E-Gun Using Stripe-Patterned Alloy Substrate for X-Ray Applications.

Author

Lim, Jongmin, Gupta, Amar P., Yeo, Seung Jun, Kong, Moonkyoo, Cho, Chong-Gil, Kim, Seung Hoon, Ahn, Jeung Sun, Mativenga, Mallory, and Ryu, Jehwang

Subjects
X-rays, FIELD emission, ALLOYS, ELECTRON gun, X-ray imaging
Abstract

We report the enhancement of carbon nanotube (CNT) field emitters by growing them directly on stripe-patterned alloy substrates. For a gate voltage of 1300 V, CNT field emitters grown on full and stripe-patterned alloy substrates achieved respective emission currents of 0.22 and 2.32 mA, corresponding to tenfold performance enhancement. Performance enhancement is attributed to the reduced screening effect (as a result of the spacing between strips) during field emission and a damage-free patterning process. To verify the ability of the stripe-patterned CNT field emitters to generate X-rays, we designed and assembled an electron gun through brazing. With the open type X-ray system, an X-ray image of human teeth was successfully obtained, verifying the potential of the stipe-patterned CNT emitters in X-ray applications. [ABSTRACT FROM AUTHOR]

Published
2019
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148. A Relationship Extraction Method from Literary Fiction Considering Korean Linguistic Features

Author

Ahn, Hee-Jeong, Kee-Won Kim, and Kim, Seung-Hoon

Subjects
Korean linguistic feature, literary fiction, Data mining, relationship extraction
Abstract

The knowledge of the relationship between characters can help readers to understand the overall story or plot of the literary fiction. In this paper, we present a method for extracting the specific relationship between characters from a Korean literary fiction. Generally, methods for extracting relationships between characters in text are statistical or computational methods based on the sentence distance between characters without considering Korean linguistic features. Furthermore, it is difficult to extract the relationship with direction from text, such as one-sided love, because they consider only the weight of relationship, without considering the direction of the relationship. Therefore, in order to identify specific relationships between characters, we propose a statistical method considering linguistic features, such as syntactic patterns and speech verbs in Korean. The result of our method is represented by a weighted directed graph of the relationship between the characters. Furthermore, we expect that proposed method could be applied to the relationship analysis between characters of other content like movie or TV drama., {"references":["D. K. Elson, D. Nicholas and K. R. McKeown, \"Extracting social networks from literary fiction\", Proceedings of the 48th annual meeting of the association for computational linguistics, pp. 138-147, Jul 2010","H. He, D. Barbosa and G. Kondrak, \"Identification of Speakers in Novels\", ACL (1), pp.1312-1320, Aug 2013","G. M. Park, S. H. Kim and H. G. Cho, \"Complex system analysis of social networks extracted from literary fictions\" International Journal of Machine Learning and Computing, vol.3, pp. 107-111, Feb 2013.","C. Y. Jung, Y. H. Seo, \"Machine Translation of Korean-to-English spoken language Based on Semantic Patterns\", Korea Information Processing Society, vol. 5, issue 9, pp. 2361-2368, 1998.","H. G. Lee, M.S. Choi, H. S. Kim, \"One-Class Classification Model Based on Lexical Information and Syntactic Patterns\", Jour nal of KIISE, vol. 42, pp. 817-822, 2015.","H. G. Yoon, S. B. Park, \"Pattern and Instance Generation for Self-knowledge Learning in Korean\" Journal of Korean Institute of Intelligent Systems, vol.25, pp. 63-69, Jan 2015.","Hannanum, http://semanticweb.kaist.ac.kr/home/index.php/HanNanum, 2014.","S. H. Kim, T. K. Park, S. H. Kim, \"A Recognition Method for Main Characters Name in Korean Novels\", The Journal of Korea Institute of Information, Electronics, and Communication Technology, vol. 9, no. 1 pp. 75-98, Feb 2016."]}

Published
2016
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