84 results on '"Honggon Kim"'
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2. Pt black catalyzed methane oxidation to methyl bisulfate in H2SO4-SO3
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Honggon Kim, Hee Won Lee, Minserk Cheong, Jeong-Myeong Ha, Ung Lee, Huyen Tran Dang, Hyunjoo Lee, and Jungho Jae
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010405 organic chemistry ,Chemistry ,Vacuum distillation ,010402 general chemistry ,01 natural sciences ,Decomposition ,Catalysis ,Oleum ,0104 chemical sciences ,chemistry.chemical_compound ,Methyl bisulfate ,Yield (chemistry) ,Anaerobic oxidation of methane ,Physical and Theoretical Chemistry ,Selectivity ,Nuclear chemistry - Abstract
Although chloride-ligated Pt compounds like (bpym)PtCl 2 , K 2 PtCl 4 , and (DMSO) 2 PtCl 2 has been reported to be highly active catalysts for the methane oxidation to methyl bisulfate (MBS) in oleum media, their applications is hampered by the catalyst deactivation to PtCl 2 . In this study, we investigated Pt black catalyzed methane oxidation, which has no ligand. A MBS yield of 82.1% with a selectivity of 96.5% was obtained at a catalyst loading of 1.6 mM at 180 °C, which proved the highest catalytic activity of Pt-black for this reaction. The reaction was thought to proceed by the dissolved Pt species, and no deactivation was observed during four consecutive experiments. However, at a concentration of over 30 mM, MBS yield fell due to the decomposition of MBS to CO 2 on the surface of heterogeneous Pt(0). Vacuum distillation experiments showed the potential for isolating MBS from the oxidation product mixture as a major component. more...
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- 2019
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Catalog
3. Reversible absorption of SO2 with alkyl-anilines: The effects of alkyl group on aniline and water
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Honggon Kim, Huyen Thanh Vo, Jungho Jae, Shin Hye Cho, Ung Lee, and Hyunjoo Lee
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chemistry.chemical_classification ,Steric effects ,General Chemical Engineering ,Salt (chemistry) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Bisulfite ,symbols.namesake ,chemistry.chemical_compound ,Aniline ,chemistry ,Absorption capacity ,symbols ,Absorption (chemistry) ,0210 nano-technology ,Raman spectroscopy ,Alkyl - Abstract
SO2 absorption behaviours of N,N-dimethylaniline (DMA), N,N-diethylaniline (DEA), N,N-dibutylaniline (DBA), and N-methyldiphenylamine (MDPA) — were investigated in dry and wet conditions. DMA showed the highest SO2 absorption capacity of 1.5 molSO2 molAbsorbent−1 in dry condition, while DBA showed the highest capacity of 1.75 molSO2 molAbsorbent−1 in wet condition. Raman analyses revealed that anilines captured SO2 by forming charge transfer complexes in dry condition and the interaction between SO2 and aniline decreased as the steric hindrance of alkyl aniline increased. In contrast, bisulfite-based acid-base salt was formed in the presence of water, and the capacity increased with an increasing basicity of the alkyl aniline. more...
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- 2019
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4. Dehydrogenation of formic acid using molecular Rh and Ir catalysts immobilized on bipyridine-based covalent triazine frameworks
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Gunniya Hariyanandam Gunasekar, Sungho Yoon, and Honggon Kim
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Renewable Energy, Sustainability and the Environment ,Formic acid ,Energy Engineering and Power Technology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Metal ,chemistry.chemical_compound ,Bipyridine ,Fuel Technology ,chemistry ,Covalent bond ,visual_art ,Polymer chemistry ,visual_art.visual_art_medium ,Dehydrogenation ,0210 nano-technology ,Triazine - Abstract
In this study, catalytic dehydrogenation of formic acid into H2/CO2 using half-sandwich Rh(III)/Ir(III) catalysts immobilized on variable dimensions of bipyridine-based covalent triazine frameworks (bpy-CTFs) has been described for the first time with a highest initial turnover frequency of 7930 h−1. A systematic study on the influence of the central metal cation (Rh vs. Ir), CTF architectures and amount of metal loadings on the CTF is presented. more...
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- 2019
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5. Copper Indium Selenide Solar Cells Fabricated from Electrodeposited Copper/Indium Multi-Stacked Precursors and a Three-Step Selenization Process
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Yong Hun Kwon, Hyun Woo Do, Hyung Koun Cho, Young-Il Park, Honggon Kim, and Yong-Hoon Kim
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chemistry.chemical_compound ,Materials science ,chemistry ,Chemical engineering ,Selenide ,Scientific method ,chemistry.chemical_element ,General Materials Science ,Copper ,Indium - Published
- 2018
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6. Exceptionally stable Rh-based molecular catalyst heterogenized on a cationically charged covalent triazine framework support for efficient methanol carbonylation
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Honggon Kim, KwangHo Park, Sungho Yoon, Joon Hyun Baik, Sangyup Lim, and Kwang-Deog Jung
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010405 organic chemistry ,Methyl acetate ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Metal ,Acetic acid ,chemistry.chemical_compound ,chemistry ,Covalent bond ,visual_art ,Polymer chemistry ,visual_art.visual_art_medium ,Methanol ,Carbonylation ,Triazine - Abstract
Direct carbonylation of methanol into methyl acetate and acetic acid using Rh-based heterogeneous catalysts is of great interest due to their effective levels of activity and stability. Here, a Rh-based molecular catalyst heterogenized on a charged 1,3-bis(pyridyl)imidazolium-based covalent triazine framework (Rh-bpim-CTF) was synthesized and characterized to have a single-site distribution of metal molecular species throughout the support by its ligation to abundant N atom sites. Methanol carbonylation was performed using the Rh-bpim-CTF catalyst in a plug-flow reaction in the gas phase, affording a turnover frequency of up to 3693 h−1 and a productivity of 218.9 mol kg−1 h−1 for acetyl products with high stability. more...
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- 2018
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7. Catalytic dehydrofluorination of 1,1,1,2,3-pentafluoropropane (HFC-245eb) to 2,3,3,3-tetrafluoropropene (HFO-1234yf) using in-situ fluorinated chromium oxyfluoride catalyst
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Seoyeon Lim, Dong Jin Suh, Hyunjoo Lee, Chang Soo Kim, Jeong-Myeong Ha, Byoung Sung Ahn, Honggon Kim, Kwang Ho Song, Min Soo Kim, Sang Deuk Lee, and Jae Wook Choi
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In situ ,Materials science ,010405 organic chemistry ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Ozone depletion potential ,01 natural sciences ,Catalysis ,Pentafluoropropane ,0104 chemical sciences ,Refrigerant ,chemistry.chemical_compound ,Chromium ,chemistry ,2,3,3,3-Tetrafluoropropene ,Fluorine - Abstract
As part of an effort to prepare a refrigerant with zero ozone depletion potential (ODP) and with a low global warming potential (GWP), the catalytic dehydrofluorination of 1,1,1,2,3-tetrafluoropropane (HFC-245eb) is performed to produce 2,3,3,3-tetrafluoropropene (HFO-1234yf). Cr2O3 prepared by the sol-gel method (Cr2O3(SG)) exhibits good catalytic activity attributable to the formation of surface chromium oxyfluoride, which exhibits better catalytic activity with high-valent chromium and a larger fluorine content. The formation of chromium oxyfluoride from chromium oxide is achieved by in-situ fluorination in the early stage of dehydrofluorination, avoiding the conventional fluorination method using toxic HF. more...
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- 2017
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8. Electrospun Mo-doped BiVO4 photoanode on a transparent conductive substrate for solar water oxidation
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Yun Jeong Hwang, Sang Youn Chae, Honggon Kim, Hyejin Jung, and Byoung Koun Min
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Nanostructure ,Materials science ,Process Chemistry and Technology ,Doping ,Substrate (chemistry) ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Tin oxide ,01 natural sciences ,Catalysis ,Electrospinning ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Bismuth vanadate ,0210 nano-technology ,Porosity - Abstract
Molybdenum-doped porous bismuth vanadate (BiVO 4 ) nanostructures were successfully synthesized on a fluorine-doped tin oxide (FTO) substrate by a simple electrospinning technique. These nanostructures were used as the photoanode for solar water oxidation. Post hot-pressing treatment was crucial in improving the photocurrents of electrospun BiVO 4 by contributing to their adhesion on the substrate and for charge separation. more...
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- 2016
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9. Enhancement of Organic Photovoltaic Efficiency via Nanomorphology Control using Conjugated Polymers Incorporating Fullerene Compatible Side-Chains
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Kyungwon Kwak, Cheol Hong Cheon, Doh Kwon Lee, Tae In Ryu, Hyunjung Kim, Hae Jung Son, Gukil Ahn, Sungmin Park, Min Jae Ko, Jin Young Kim, Honggon Kim, Nam-Gyu Park, Dongkyun Seo, and Bongsoo Kim
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chemistry.chemical_classification ,Materials science ,Fullerene ,Polymers and Plastics ,Organic Chemistry ,Electronic structure ,Polymer ,Conjugated system ,Miscibility ,Inorganic Chemistry ,Chemical engineering ,chemistry ,Polymer chemistry ,Materials Chemistry ,Side chain ,Copolymer ,Charge carrier - Abstract
We present controls of nanomorphology of polymer:fullerene BHJ films via synthesis of a series of push–pull-type copolymers with various molar percentages of side chains terminated with o-dichlorobenzyl (DCBZ) groups. As the molar percentage of the DCBZ-containing repeat units increases, the miscibility of the polymers in the series with PC71BM increases with respect to that of the polymer (PTBBO) that does not contain DCBZ. In the optimal film morphology, which consists of a polymer containing 25 mol % DCBZ-terminated side chains in the electron-pull unit (PTBDCB25), the polymer/PC71BM interface area is sufficiently large for efficient charge separation and percolated pathways is present for efficient charge carrier transport. In contrast, the BHJ film prepared from PTBBO has smaller interfaces and larger PC71BM aggregates. Furthermore, the intermolecular interaction between PC71BM and DCBZ induced changes in the PC71BM’s electronic structure at the polymer:PC71BM interface, resulting in an increase of t... more...
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- 2015
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10. Influences of Extended Selenization on Cu2ZnSnSe4 Solar Cells Prepared from Quaternary Nanocrystal Ink
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Doh Kwon Lee, Seung Yong Lee, Min Jae Ko, Bongsoo Kim, Jae-Seung Lee, So Hye Cho, Bo-In Park, Hae Jung Son, Yoonjung Hwang, Jeung Hyun Jeong, Honggon Kim, Byung-Seok Lee, Jin Young Kim, and Jong Ku Park more...
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Materials science ,Equivalent series resistance ,Annealing (metallurgy) ,Nanotechnology ,engineering.material ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Dielectric spectroscopy ,law.invention ,chemistry.chemical_compound ,General Energy ,chemistry ,Chemical engineering ,Nanocrystal ,law ,Solar cell ,engineering ,CZTS ,Kesterite ,Physical and Theoretical Chemistry ,Thin film - Abstract
Kesterite Cu2ZnSnSe4 (CZTSe) thin films prepared by the selenization of mechanochemically synthe- sized Cu2ZnSnS4 (CZTS) nanocrystal films are systematically investigated as a function of the annealing time in terms of the phase purity, microstructure, composition, and device characteristics. It is shown that selenization for an extended time does not cause a noticeable amount of Sn loss or segregation of Zn-rich layers. Thus, the prolonged annealing leads to improvements (reduction) in the shunt conductance, reverse saturation current, and diode ideality factor. However, it also leads to a deterioration of the series resistance, of which influence turned out to overwhelm all of the aforementioned positive effects on the device performance. As a consequence, the CZTSe solar cell exhibits its highest efficiency (5.43%) at the shortest annealing time (10 min). Impedance spectroscopy is demonstrated to be of good use in detecting the change in the back contact of CZTSe solar cells during annealing. The impedance spectra of the CZTSe solar cells are analyzed in association with the microstructures of the back-contact electrodes, demonstrating that the increase in the series resistance is attributed to the formation of the resistive MoSe2 layer. more...
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- 2014
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11. Simultaneous Enhancement of Solar Cell Efficiency and Photostability via Chemical Tuning of Electron Donating Units in Diketopyrrolopyrrole-Based Push–Pull Type Polymers
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Doh-Kwon Lee, Do-Hoon Hwang, Hae Jung Son, Min Jae Ko, BongSoo Kim, Nam-Gyu Park, Tae In Ryu, Honggon Kim, Youngwoon Yoon, Ji-Hoon Kim, and Jin Young Kim
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Band gap ,Organic Chemistry ,Energy conversion efficiency ,Stacking ,Polymer ,Photochemistry ,Inorganic Chemistry ,Delocalized electron ,Solar cell efficiency ,chemistry ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Charge carrier - Abstract
We synthesized a series of push–pull-type copolymers by copolymerizing an electron-deficient diketopyrrolopyrrole with three electron-donating benzodithiophene (BDT) moieties. PDPPDTT, which incorporated a dithienothiophene (DTT), showed a higher power conversion efficiency (PCE) of 6.11% compared to 3.31% for the BDT-based polymer (PDPPBDT). PDPPDTBDT, which incorporated a dithienobenzodithiophene (DTBDT), also exhibited superior performance, with a PCE of 4.75% although this value was lower than that obtained for PDPPDTT. The presence of the DTT unit in the polymer backbone lowered the energy bandgap of the polymer and induced an optimal morphology in the polymer:PC71BM blend film, resulting in higher charge carrier generation. Furthermore, the effectively delocalized frontier orbitals of PDPPDTT enhanced intermolecular interactions between the polymer chains by favoring effective π–π stacking, which facilitated charge carrier transport. By contrast, PDPPDTBDT unexpectedly showed a low-crystallinity thi... more...
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- 2014
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12. Effect of asymmetric solubility of diketopyrrolopyrrole-based polymers and PC71BMs in a binary solvent system on the performance of bulk heterojunction solar cells
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Min Jae Ko, Sungnam Park, Hyo Sang Lee, Seon Kyoung Son, Bongsoo Kim, Jae Seung Ha, Donghoon Choi, Honggon Kim, Hae Jung Son, Doh Kwon Lee, Wonmok Lee, Kyung Hwan Kim, and Jin Young Kim
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chemistry.chemical_classification ,Chloroform ,Materials science ,Fullerene ,Organic solar cell ,Renewable Energy, Sustainability and the Environment ,Polymer ,Polymer solar cell ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Solvent ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Polymer chemistry ,Molecule ,Solubility - Abstract
In this study, we demonstrated the effective morphological control of polymer:fullerene blends using three separate solvent systems: chloroform (CF), CF:1,8-diiodooctane (DIO), and CF:o-dichlorobenzene (ODCB). The polymer:fullerene blends are composed of two diketopyrrolopyrrole (DPP)-based polymers of P(DPP-alt-QT) and P(DPP-alt-DTBSe) and a fullerene derivative of [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), i.e., P(DPP-alt-QT):PC71BM or P(DPP-alt-DTBSe):PC71BM. The CF:ODCB binary solvent exhibited the best photovoltaic performance among the three solvent systems for both polymer-based devices, although the CF:DIO also exhibited an improved performance compared to the CF system. By examining film morphology of the blend films, we found that the CF:ODCB enabled the most optimal nanoscale phase separation and the morphological features were strongly affected by the solubility of each material in the high boiling-point (BP) solvent. Specifically, the polymers have limited but slightly higher solubility in ODCB than in DIO, while the PC71BM molecules have a high solubility in both DIO and ODCB. Therefore, this work highlights that the optimally asymmetric solubility of each photoactive component in the high BP solvent is a critical factor to form the nanoscale, bicontinuous domains in the blend films and thereby to determine the performance of photovoltaic devices. more...
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- 2014
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13. Highly Efficient Copper-Zinc-Tin-Selenide (CZTSe) Solar Cells by Electrodeposition
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Hae Jung Son, Jeung-hyun Jeong, Lee Seul Oh, Bongsoo Kim, Doh-Kwon Lee, Min Jae Ko, Se-Won Seo, Jong-Ok Jeon, Honggon Kim, Jin Young Kim, and Kee Doo Lee
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Materials science ,Annealing (metallurgy) ,General Chemical Engineering ,chemistry.chemical_element ,Nanotechnology ,Crystal growth ,law.invention ,Selenium ,Crystallinity ,chemistry.chemical_compound ,Electric Power Supplies ,law ,Solar Energy ,Environmental Chemistry ,General Materials Science ,Thin film ,Crystallization ,Tin selenide ,Energy conversion efficiency ,Electroplating ,Copper ,Zinc ,General Energy ,Chemical engineering ,chemistry ,Tin - Abstract
Highly efficient copper-zinc-tin-selenide (Cu2ZnSnSe4 ; CZTSe) thin-film solar cells are prepared via the electrodepostion technique. A metallic alloy precursor (CZT) film with a Cu-poor, Zn-rich composition is directly deposited from a single aqueous bath under a constant current, and the precursor film is converted to CZTSe by annealing under a Se atmosphere at temperatures ranging from 400 °C to 600 °C. The crystallization of CZTSe starts at 400 °C and is completed at 500 °C, while crystal growth continues at higher temperatures. Owing to compromises between enhanced crystallinity and poor physical properties, CZTSe thin films annealed at 550 °C exhibit the best and most-stable device performances, reaching up to 8.0 % active efficiency; among the highest efficiencies for CZTSe thin-film solar cells prepared by electrodeposition. Further analysis of the electronic properties and a comparison with another state-of-the-art device prepared from a hydrazine-based solution, suggests that the conversion efficiency can be further improved by optimizing parameters such as film thickness, antireflection coating, MoSe2 formation, and p-n junction properties. more...
- Published
- 2014
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14. Correlation between Polymer Structure and Polymer:Fullerene Blend Morphology and Its Implications for High Performance Polymer Solar Cells
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Youn Su Kim, Jin Young Kim, Donghoon Choi, Kyungkon Kim, Honggon Kim, Min Jae Ko, Seon Kyoung Son, Doh Kwon Lee, Hae Jung Son, and Bongsoo Kim
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chemistry.chemical_classification ,Fullerene ,Materials science ,Polymer ,Acceptor ,Polymer solar cell ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,Terthiophene ,Photoactive layer ,chemistry ,Polymer chemistry ,Moiety ,Physical and Theoretical Chemistry ,Solubility - Abstract
We synthesized four polymers (pT3DPP-HD, pT3DPP-OD, pT2TTDPP-HD, and pT2TTDPP-OD) and characterized their photovoltaic properties as a function of the backbone planarity, alkyl side chain length, and film morphology. The polymers were donor–acceptor type low-band-gap (1.2–1.3 eV) polymers employing terthiophene (T3) or thiophene–thieno[3,2-b]thiophene–thiophene (T2TT) as the donor and 2,5-bis(2-hexyldecyl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione (DPP-HD) or 2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione (DPP-OD) as the acceptor. The T2TT moiety in the polymer backbone is more planar than the T3; the OD moiety as the alkyl side chain ensured a higher solubility than the HD moiety. Polymer solar cells (PSCs) were fabricated, and their properties were characterized. The photoactive layer consisted of one of the four polymers and one of the fullerene derivatives (PC70BM or PC60BM). For a given fullerene derivative, the PCEs prepared with each of the four polymers were ordered according to pT3DP... more...
- Published
- 2014
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15. Differences in bifunctionality of ZnO and ZrO2 in Cu/ZnO/ZrO2/Al2O3 catalysts in hydrogenation of carbon oxides for methanol synthesis
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Honggon Kim, Sungho Yoon, Imran Abbas, Chae-Ho Shin, and Kwang-Deog Jung
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Hydrogen ,Process Chemistry and Technology ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Carbon oxide ,Composition (visual arts) ,Methanol ,0210 nano-technology ,General Environmental Science - Abstract
This work investigates the promotional roles of ZrO2 and ZnO for methanol synthesis on five Cu6Zn3.0-xZrxAl1 (x = 0.0, 0.5, 1.5, 2.5, 3.0) catalysts in the various CO2 feed composition. TOF decreased with an increase in x of Cu6Zn3.0-xZrxAl1 catalysts in the 5% CO2 feed, while TOF is maximized over Cu6Zn1.5Zr1.5Al1 in the 100% CO2 feed. Both the effects of Zn (reverse spillover) and Zr (additional reaction sites) in the vicinity of Cu promote the CO2 hydrogenation, maximizing the catalytic activity of Cu6Zn1.5Zr1.5Al1 in the 100% CO2 feed. The migration of hydrogen on ZrO2 can be limited in little surface hydroxyls in 5% CO2 feed, which can be a reason for the negative role of ZrO2 in the 5% CO feed. The promotional effect of ZrO2 on Cu/ZnO is important only for high CO2 feed more than 50% CO2. more...
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- 2019
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16. Synthesis of phenanthro[1,10,9,8-cdefg]carbazole-based conjugated polymers for organic solar cell applications
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Hae Jung Son, Youngwoon Yoon, Honggon Kim, Doh-Kwon Lee, Soon-Ki Kwon, So Min Park, Chan Woo Jeon, Bong-Soo Kim, Min Jae Ko, Jin Young Kim, and Yun-Hi Kim
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Organic solar cell ,Carbazole ,Organic Chemistry ,Polymer ,Conjugated system ,Miscibility ,chemistry.chemical_compound ,Quinoxaline ,chemistry ,Polymer chemistry ,Materials Chemistry ,Alkoxy group ,Phenyl group - Abstract
Low bandgap polymers with dithienylquinoxaline moieties based on 6H-phenanthro[1,10,9,8-cdefg]carbazole were synthesized via the Suzuki coupling reaction. Alkoxy groups were substituted at two different positions on the phenyl groups of the quinoxaline units of these polymers: in the para-position (PPQP) and in the meta-position (PPQM). The two polymers showed similar physical properties: broad absorption in the range of 400–700 nm, optical bandgaps of ∼1.8 eV, and the appropriate frontier orbital energy levels for efficient charge transfer/separation at polymer/PC71BM interfaces. However, the PPQM solar cell achieved a higher PCE due to its higher Jsc. Our investigation of the morphologies of the polymer:PC71BM blend films and theoretical calculations of the molecular conformations of the polymer chains showed that the polymer with the meta-positioned alkoxy group has better miscibility with PC71BM than the polymer with the para-positioned alkoxy group because the dihedral angle of its phenyl group with respect to the quinoxaline unit is higher. This higher miscibility resulted in a polymer:PC71BM blend film with a better morphology and thus in a higher PCE. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 796–803 more...
- Published
- 2013
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17. Preparation of Cu2ZnSnS4 thin films via electrochemical deposition and rapid thermal annealing
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Bongsoo Kim, Jeung Hyun Jeong, Doh Kwon Lee, Min Jae Ko, Honggon Kim, Se Won Seo, Jin Young Kim, Kee Doo Lee, and Donghwan Kim
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Materials science ,Aqueous solution ,Metallurgy ,Metals and Alloys ,Surfaces and Interfaces ,Electrochemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,chemistry.chemical_compound ,symbols.namesake ,Chemical engineering ,chemistry ,visual_art ,Phase (matter) ,Materials Chemistry ,visual_art.visual_art_medium ,symbols ,Deposition (phase transition) ,CZTS ,Thin film ,Raman spectroscopy - Abstract
We fabricated metallic Cu–Zn–Sn (CZT) precursor thin films via electrochemical deposition from aqueous metal salt solution on Mo-coated soda-lime glass substrates, and the influence of the subsequent sulfurization condition on the morphology, composition and structure of the final Cu2ZnSnS4 (CZTS) thin films was investigated. A rapid thermal annealing equipment was used for a systematic control of the sulfurization process parameters. The as-deposited films are composed of binary metallic alloys, which can be converted to the highly crystalline CZTS phase after sulfurization at temperatures above 500 °C. The composition of the CZT film barely changes during the sulfurization, and a small amount of CuS-based secondary phases exists even at 550 °C. However, a quick post-annealing KCN treatment effectively and selectively removes the secondary phase, evidenced by the Raman spectroscopy and elemental. more...
- Published
- 2013
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18. Reversed organic–inorganic hybrid tandem solar cells for improved interfacial series resistances and balanced photocurrents
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Taehee Kim, Sunwoo Moon, Doh Kwon Lee, Kyungkon Kim, Jin Young Kim, Honggon Kim, Jun Hong Jeon, Bongsoo Kim, Seunghee Han, Jin-Young Choi, Min Jae Ko, Sung Min Kim, Won Woong Park, and Youn Su Kim
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Amorphous silicon ,Materials science ,Tandem ,Organic solar cell ,Equivalent series resistance ,business.industry ,Band gap ,Mechanical Engineering ,Photovoltaic system ,Metals and Alloys ,Analytical chemistry ,Chemical vapor deposition ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Materials Chemistry ,Transmittance ,Optoelectronics ,business - Abstract
We report a promising approach to fabricate organic–inorganic hybrid tandem photovoltaic devices with a reversed configuration. High bandgap hydrogenated amorphous silicon (a-Si:H) was deposited with plasma-enhanced chemical vapor deposition onto a solution-processed low bandgap organic photovoltaic (OPV) subcell. Two important factors for efficient tandem solar cells, interfacial series resistance (RS,int) and balanced photocurrents, were investigated. The intimate interfacial contact eliminated the RS,int, and sufficient transmittance of the OPV front subcell led to the well-balanced photocurrents. As a result, this reversed hybrid tandem device showed an enhanced efficiency of 3.3% and an open-circuit voltage of 1.51 V. more...
- Published
- 2013
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19. Correlation between Crystallinity, Charge Transport, and Electrical Stability in an Ambipolar Polymer Field-Effect Transistor Based on Poly(naphthalene-alt-diketopyrrolopyrrole)
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Joong Seok Lee, Sungnam Park, Honggon Kim, Hae Jung Son, Moon Sung Kang, Bongsoo Kim, Sanghyeok Cho, Se Young Oh, Hyunjung Kim, Jeong Ho Cho, Min Jae Ko, Hyo Sang Lee, and Beom Joon Kim
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chemistry.chemical_classification ,Electron mobility ,Materials science ,Annealing (metallurgy) ,Ambipolar diffusion ,Analytical chemistry ,Polymer ,Electron ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Crystallinity ,General Energy ,chemistry ,Polymer chemistry ,Field-effect transistor ,Physical and Theoretical Chemistry ,Naphthalene - Abstract
We characterized the electrical properties of ambipolar polymer field-effect transistors (PFETs) based on the low-band-gap polymer, pNAPDO-DPP-EH. The polymer consisted of electron-rich 2,6-di(thienyl)naphthalene units with decyloxy chains (NAPDO) and electron-deficient diketopyrrolopyrrole units with 2-ethylhexyl chains (DPP-EH). The as-spun pNAPDO-DPP-EH PFET device exhibited ambipolar transport properties with a hole mobility of 3.64 × 10–3 cm2/(V s) and an electron mobility of 0.37 × 10–3 cm2/(V s). Thermal annealing of the polymer film resulted in a dramatic increase in the carrier mobility. Annealing at 200 °C yielded hole and electron mobilities of 0.078 and 0.002 cm2/(V s), respectively. The mechanism by which the mobility had improved was investigated via grazing incidence X-ray diffraction studies, atomic force microscopy, and temperature-dependent transport measurements. These results indicated that thermal annealing improved the polymer film crystallinity and promoted the formation of a longer... more...
- Published
- 2013
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20. Rapid Dye Adsorption via Surface Modification of TiO2 Photoanodes for Dye-Sensitized Solar Cells
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Honggon Kim, Hae Jung Son, Jin Young Kim, Kicheon Yoo, Boeun Kim, Bongsoo Kim, Se Woong Park, Min Woo Lee, Min Jae Ko, Jae-Yup Kim, Jin Ah Lee, Doh-Kwon Lee, and Sung-Hwan Han
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Reaction rate ,Chemical kinetics ,chemistry.chemical_compound ,Dye-sensitized solar cell ,Adsorption ,Aqueous solution ,chemistry ,Nitric acid ,Surface modification ,chemistry.chemical_element ,General Materials Science ,Photochemistry ,Ruthenium - Abstract
A facile method for increasing the reaction rate of dye adsorption, which is the most time-consuming step in the production of dye-sensitized solar cells (DSSCs), was developed. Treatment of a TiO2 photoanode with aqueous nitric acid solution (pH 1) remarkably reduced the reaction time required to anchor a carboxylate anion of the dye onto the TiO2 nanoparticle surface. After optimization of the reaction conditions, the dye adsorption process became 18 times faster than that of the conventional adsorption method. We studied the influence of the nitric acid treatment on the properties of TiO2 nanostructures, binding modes of the dye, and adsorption kinetics, and found that the reaction rate improved via the synergistic effects of the following: (1) electrostatic attraction between the positively charged TiO2 surface and ruthenium anion increases the collision frequency between the adsorbent and the anchoring group of the dye; (2) the weak anchoring affinity of NO3(-) in nitric acid with metal oxides enables the rapid coordination of an anionic dye with the metal oxide; and (3) sufficient acidity of the nitric acid solution effectively increases the positive charge density on the TiO2 surface without degrading or transforming the TiO2 nanostructure. These results demonstrate the developed method is effective for reducing the overall fabrication time without sacrificing the performance and long-term stability of DSSCs. more...
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- 2013
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21. N-Octyl-2,7-dithia-5-azacyclopenta[a]pentalene-4,6-dione-Based Low Band Gap Polymers for Efficient Solar Cells
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Il Kang, Bongsoo Kim, Youngwoon Yoon, Nara Shin, Yun-Hi Kim, Min Jae Ko, Hae Jung Son, Youn Su Kim, Seul Ong Kim, Kyungkon Kim, Honggon Kim, Hui Jun Yun, and Soon Ki Kwon
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chemistry.chemical_classification ,Materials science ,Pentalene ,Polymers and Plastics ,Band gap ,business.industry ,Organic Chemistry ,Polymer ,Photochemistry ,Acceptor ,law.invention ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,PEDOT:PSS ,law ,Solar cell ,Materials Chemistry ,Optoelectronics ,Moiety ,business ,HOMO/LUMO - Abstract
We report the synthesis, characterization, and solar cell properties of new donor–acceptor-type low band gap polymers (POBDTPD and PEBDTPD) that incorporate dialkoxybenzodithiophene (BDT) as the donor and N-octyl-2,7-dithia-5-azacyclopenta[a]pentalene-4,6-dione (DTPD) as the acceptor. The newly developed DTPD moiety was carefully designed to lower a band gap via strong interaction between donor–acceptor moieties and keep polymer energy levels deep. Remarkably, the DTPD acceptor moiety effectively widens the light absorption range of the polymers up to ∼900 nm while positioning their HOMO and LUMO levels in the optimal range, i.e., −5.3 and −4.0 eV, respectively, for high power conversion efficiencies (PCEs) as we intended. Solar cell devices were fabricated according to the structure ITO/PEDOT:PSS/photoactive (polymer:PC70BM)/TiO2/Al. The POBDTPD devices exhibited a PCE of 4.7% with a Voc of 0.70 V, a Jsc of 10.6 mA/cm2, and a FF of 0.64. The PEBDTPD devices yielded a higher PCE of 5.3% with a Voc of 0.72... more...
- Published
- 2013
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22. Synthesis and characterization of wide range light absorbing poly(dithieno[3,2-b:2′,3′-d]thiophene-alt-3,6-bis(thiophen-2-yl)-2,5-di-n-octyl-pyrrolo[3,4-c]pyrrole-1,4-dione) for polymer solar cells
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Doh Kwon Lee, Bongsoo Kim, Youngwoon Yoon, Kyung Hwan Kim, Min Woo Lee, C. Y. Lee, Min Jae Ko, Donghoon Choi, Kyungkon Kim, and Honggon Kim
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chemistry.chemical_classification ,Materials science ,Band gap ,Mechanical Engineering ,Metals and Alloys ,Polymer ,Condensed Matter Physics ,Polymer solar cell ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,PEDOT:PSS ,Mechanics of Materials ,Polymer chemistry ,Materials Chemistry ,Thiophene ,Thermal stability ,Glass transition ,HOMO/LUMO - Abstract
We designed and synthesized a new low band gap donor–acceptor copolymer (PDTDPP-Oct) composed of alternating dithieno[3,2- b :2′,3′- d ]thiophene and bis-thienyl-diketopyrrolo[3,4- c ]pyrrole units. The polymer films showed a very broad absorption band that extended up to 950 nm. Thermogravimetric analysis revealed good thermal stability and a high glass transition temperature of 128 °C. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the polymer were estimated to be −5.01 and −3.70 eV, respectively. Bulk heterojunction polymer solar cells were fabricated with the structure: ITO/PEDOT:PSS/polymer:PCBM/Al. The introduction of 1,8-octanedithiol as a processing additive to the polymer/PCBM blend solution significantly improved the device performance relative to devices prepared from the blend solution without the additive. This cell gave a short circuit current of −1.8 mA/cm 2 , an open circuit voltage of 0.60 V, and a fill factor of 0.52, yielding a power conversion efficiency of 0.55%. The performance improvements were mainly attributed to the fine morphology of the blend film. more...
- Published
- 2013
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23. Highly dense and crystalline CuInSe2 thin films prepared by single bath electrochemical deposition
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Kyungwon Seo, Doh Kwon Lee, Wonjoo Lee, Kyungkon Kim, Min Jae Ko, Honggon Kim, Hana Lee, and Jin Young Kim
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Materials science ,General Chemical Engineering ,Nanotechnology ,Microstructure ,Copper indium gallium selenide solar cells ,law.invention ,chemistry.chemical_compound ,Crystallinity ,chemistry ,Chemical engineering ,law ,Selenide ,Solar cell ,Electrochemistry ,Deposition (phase transition) ,Relative density ,Thin film - Abstract
Chalcopyrite CIS or CIGS have been regarded as promising absorbing materials for thin-film solar cells with widespread commercialization prospects. The most critical material properties of a CIS absorption layer that affect the overall PV performance include its microstructure and composition at a given bandgap energy. In this study, dense CISe films with high crystallinity and uniform, flat surfaces were fabricated on In2Se3/ITO employing single bath electrochemical deposition by adjusting the deposition parameters, such as the precursor concentration, pH, and applied potential. A simple formula is presented based on Faraday's law to quantitatively estimate the density of the electrodeposited thin films; from this, it was found that the as-deposited films had a very high relative density of 0.73. The high green density of the as-deposited film led to the full densification of the CISe film with ca. 10 μm sized grains. The binary selenide phase remaining in the sintered film was subsequently etched out using a KCN solution, resulting in an overall Cu-deficient composition in the film of [Cu]/[In] = 0.95. more...
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- 2013
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24. Crystallinity-Controlled Naphthalene-alt-diketopyrrolopyrrole Copolymers for High-Performance Ambipolar Field Effect Transistors
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Seon Kyoung Son, Jeong Ho Cho, Joong Suk Lee, Kyungwon Kwak, Sungnam Park, Doh Kwon Lee, Bongsoo Kim, Youngwoon Yoon, Jin Young Kim, Min Jae Ko, Se Young Oh, Sanghyeok Cho, Hyo Sang Lee, Honggon Kim, Hyunjung Kim, and Dong Hoon Choi more...
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chemistry.chemical_classification ,Electron mobility ,Materials science ,Band gap ,Ambipolar diffusion ,Analytical chemistry ,Polymer ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallinity ,General Energy ,Polymerization ,chemistry ,Polymer chemistry ,Field-effect transistor ,Physical and Theoretical Chemistry ,Alkyl - Abstract
We report high-performance of ambipolar organic field-effect transistors (FETs) based on the low band gap copolymers of pDPPT2NAP-HD and pDPPT2NAP-OD. The polymers are composed of electron-rich 2,6-di(thienyl)naphthalene (T2NAP) and electron-deficient diketopyrrolopyrrole (DPP) units with branched alkyl chains of 2-hexyldecyl (HD) or 2-octyldodecyl (OD). The polymers were polymerized via Suzuki coupling, yielding optical band gaps of ∼1.4 eV. In the transistor performance test, we observed good ambipolar transport behavior in both polymer films, and pDPPT2NAP-OD displayed hole and electron mobilities 1 order of magnitude higher than the corresponding properties of pDPPT2NAP-HD. Thermal annealing of the polymer films increased the carrier mobilities. Annealing at 150 °C provided optimal conditions yielding saturated film crystallinity and maximized carrier mobility. The highest hole and electron mobilities achieved in these polymers were 1.3 and 0.1 cm2/(V s), respectively, obtained from pDPPT2NAP-OD. The ... more...
- Published
- 2012
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25. Importance of 4-tert-Butylpyridine in Electrolyte for Dye-Sensitized Solar Cells Employing SnO2 Electrode
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Doh-Kwon Lee, Jin Young Kim, Honggon Kim, Jae-Yup Kim, Bongsoo Kim, and Min Jae Ko
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Open-circuit voltage ,Chemistry ,Photovoltaic system ,Energy conversion efficiency ,Analytical chemistry ,Electrolyte ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Dye-sensitized solar cell ,General Energy ,Electrode ,Physical and Theoretical Chemistry ,Short circuit ,Order of magnitude - Abstract
The photovoltaic performance of dye-sensitized solar cells (DSSCs) employing SnO2 electrodes was investigated while increasing the content of 4-tert-butylpyridine (TBP) in the conventional liquid-type electrolyte. As the added TBP content increased, the open circuit voltage (Voc) and conversion efficiency were highly enhanced while the short circuit current (Jsc) was not much affected. With the electrolyte of 2.0 M TBP, the Voc and conversion efficiency were increased by 26 and 33%, respectively, compared with the conventional electrolyte (0.5 M TBP). The electrochemical impedance spectra revealed that the enhancement of Voc resulted from the negative shift of the SnO2 conduction band potential and the increase in resistance of electron recombination by 1 order of magnitude. It is noteworthy that the optimized concentration of TBP for the SnO2 electrode is greatly larger than that for the TiO2 electrode. This may be due to the much faster electron recombination rate and more positive conduction band poten... more...
- Published
- 2012
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26. Hybrid tandem photovoltaic devices with a transparent conductive interconnecting recombination layer
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Jin-Young Choi, Taehee Kim, Bongsoo Kim, Kyungkon Kim, Honggon Kim, Doh Kwon Lee, Jun Hong Jeon, Seunghee Han, and Youn Su Kim
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Amorphous silicon ,Materials science ,Organic solar cell ,Tandem ,business.industry ,Mechanical Engineering ,Photovoltaic system ,Energy conversion efficiency ,Photovoltaic effect ,Condensed Matter Physics ,Indium tin oxide ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Optoelectronics ,General Materials Science ,Thin film ,business - Abstract
Highlights: ► This work enhanced power conversion efficiency of the hybrid tandem solar cell from 1.0% to 2.6%. ► The interfacial series resistance of the tandem solar cell was eliminated by inserting ITO layer. ► This work shows the feasibility of the highly efficient hybrid tandem solar cells. -- Abstract: We demonstrate hybrid tandem photovoltaic devices with a transparent conductive interconnecting recombination layer. The series-connected hybrid tandem photovoltaic devices were developed by combining hydrogenated amorphous silicon (a-Si:H) and polymer-based organic photovoltaics (OPVs). In order to enhance the interfacial connection between the subcells, we employed highly transparent and conductive indium tin oxide (ITO) thin layer. By using the ITO interconnecting layer, the power conversion efficiency of the hybrid tandem solar cell was enhanced from 1.0% (V{sub OC} = 1.041 V, J{sub SC} = 2.97 mA/cm{sup 2}, FF = 32.3%) to 2.6% (V{sub OC} = 1.336 V, J{sub SC} = 4.65 mA/cm{sup 2}, FF = 41.98%) due to the eliminated interfacial series resistance. more...
- Published
- 2012
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27. Size-dependent electrocatalytic activities of printed Co3O4 films for a monolithic photovoltaic-electrolytic hydrogen generation system
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Hyo Sang Jeon, Byoung Koun Min, Honggon Kim, Agung Nugroho, and Jaehoon Kim
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Hydrogen ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Mineralogy ,Overpotential ,Condensed Matter Physics ,Electrocatalyst ,Electrochemistry ,Fuel Technology ,chemistry ,Chemical engineering ,Water splitting ,Particle size ,BET theory ,Hydrogen production - Abstract
As an electrocatalyst in a monolithic PV-electrolytic cell for water splitting hydrogen generation Co3O4 films were prepared by a paste coating method using Co3O4 particles. Different sized Co3O4 particles with average diameters of 145.9, 63.3 and 36.5 nm were prepared using a supercritical hydrothermal synthesis method. Electrochemical properties with respect to the particle size in the film were investigated by evaluating overpotential, charge transfer resistance (Rct), and number of active sites (q∗). The relation between overpotential in water oxidation at 5 mA/cm2 and BET surface area showed a slope of −73.8 ± 6.6, implying strong particle size dependence on electrocatalytic activity. Moreover, the Rct and q∗ values and the actual hydrogen evolution rate indicated that the electrocatalytic activity of Co3O4 is attributed to physical properties (e.g. particle size) of the film. Whereas, intrinsic single site activity of the film was not significantly changed with respect to the particle size in the film. more...
- Published
- 2011
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28. Blocking Layers Deposited on TCO Substrate and Their Effects on Photovoltaic Properties in Dye-Sensitized Solar Cells
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Kyungkon Kim, Honggon Kim, Doh-Kwon Lee, Min Jae Ko, Nam-Gyu Park, Bongsoo Kim, and Beom-Hin Yoo
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Materials science ,Silicon ,business.industry ,Photovoltaic system ,Energy conversion efficiency ,chemistry.chemical_element ,Substrate (electronics) ,law.invention ,Dye-sensitized solar cell ,chemistry ,law ,Solar cell ,Electrochemistry ,Optoelectronics ,Plasmonic solar cell ,business ,Transparent conducting film - Abstract
In this review, we have investigated the effect of TiO 2 -based blocking layers (t-BLs), deposited ona transparent conductive oxide (TCO)-coated glass substrate, on the photovoltaic performance ofdye-sensitized solar cells (DSSCs). The t-BL was deposited using spin-coating or sputteringtechnique, and its thicknesses were varied to study the influence of the thin TiO 2 layer in betweentransparent conducting glass and nanocrystalline TiO 2 (nc-TiO 2 ). The DSSC with the t-BL showedthe improved adhesion and the suppressed charge recombination at a TCO glass substrate thanthose without the t-BL, which led to the higher conversion efficiency. Keywords: Dye-sensitized solar cell, Blocking layers, Transparent conducting oxides, Chargerecombination, Adhesion properties Received May 27, 2011 : Accepted June 3, 2011 1. Introduction Dye-sensitized solar cells have been extensivelystudied since their discovery in 1991 by Gratzel’s researchgroup 1) because they have been considered as a goodalternative to conventional silicon photovoltaic cells dueto their low production costs and colorful characteristics.As a consequence of this special attention, DSSCs withenergy conversion efficiencies higher than 11% have beenobtained using nc-TiO more...
- Published
- 2011
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29. Printed Co3O4 film as an electrocatalyst for hydrogen production by a monolithic photovoltaic-electrolysis system
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Woong Kim, Wonil Park, Jaehoon Kim, Hyo Sang Jeon, Honggon Kim, and Byoung Koun Min
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Electrolysis ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Electrolytic cell ,Energy Engineering and Power Technology ,engineering.material ,Condensed Matter Physics ,Electrocatalyst ,law.invention ,chemistry.chemical_compound ,Fuel Technology ,Coating ,Chemical engineering ,law ,Nafion ,engineering ,Water splitting ,Layer (electronics) ,Hydrogen production - Abstract
In a monolithic photovoltaic-electrolysis system, photovoltaic and catalytic layers are generally constructed on both sides of a conducting substrate. For the realization of this architecture it is critical to fabricate the catalytic layer at sufficiently low temperature in order not to deteriorate the photovoltaic photoanode that is already installed on the reverse side of the catalytic layer. In this study we demonstrate successful fabrication of Co3O4 electrocatalyst films at low temperature (∼50°C) on a stainless steel substrate by a paste coating method using Nafion as a binder. The Co3O4 films were found to be catalytically efficient and stable in water splitting reaction in an alkaline aqueous solution. More importantly, the Co3O4 films casted at low temperature (∼50°C) revealed the highest hydrogen production rate in the electrolytic cell compared to the films prepared at higher temperatures (e.g. 150 and 300°C), which would be very beneficial in the construction of a monolithic photovoltaic-electrolysis system. more...
- Published
- 2011
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30. Electrochemical Capacitors Based on Aligned Carbon Nanotubes Directly Synthesized on Tantalum Substrates
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Byungwoo Kim, Honggon Kim, Byoung Koun Min, Woong Kim, and Haegeun Chung
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Supercapacitor ,Materials science ,Equivalent series resistance ,Carbon nanofiber ,Tantalum ,chemistry.chemical_element ,Nanotechnology ,General Chemistry ,Carbon nanotube ,law.invention ,Potential applications of carbon nanotubes ,chemistry ,Chemical engineering ,Frit compression ,law ,Carbon nanotube supported catalyst - Abstract
We demonstrate that vertically aligned carbon nanotubes can be synthesized directly on tantalum substrate via waterassisted chemical vapor deposition and evaluate their properties as electrochemical capacitors. The mean diameter of the carbon nanotubes was 7.1 ± 1.5 nm, and 70% of them had double walls. The intensity ratio of G-band to D-band in Raman spectra was as high as 5, indicating good quality of the carbon nanotubes. Owing to the alignment and low equivalent series resistance, the carbon nanotube based supercapacitors showed good rate performance. Rectangular shape of cyclic voltammogram was maintained even at the scan rate of > 1 V/s in 1 M sulfuric acid aqueous solution. Specific capacitance was well-retained (~94%) even when the discharging current density dramatically increased up to 145 A/g. Consequently, specific power as high as 60 kW/kg was obtained from as-grown carbon nanotubes in aqueous solution. Maximum specific energy of ~20 Wh/kg was obtained when carbon nanotubes were electrochemically oxidized and operated in organic solution. Demonstration of direct synthesis of carbon nanotubes on tantalum current collectors and their applications as supercapacitors could be an invaluable basis for fabrication of high performance carbon nanotube supercapacitors. more...
- Published
- 2010
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31. Alkyl-fluoroalkylimidazolium-Based Ionic Liquids as Efficient CO2Absorbents
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Min Ho Cho, Honggon Kim, Hyunjoo Lee, Bang Sook Lee, Jelliarko Palgunadi, and Hoon Sik Kim
- Subjects
chemistry.chemical_classification ,chemistry.chemical_compound ,Fuel Technology ,Chemistry ,General Chemical Engineering ,Ionic liquid ,Inorganic chemistry ,Energy Engineering and Power Technology ,Organic chemistry ,Alkyl - Published
- 2010
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32. Effects of Halide Anions to Absorb SO2in Ionic Liquids
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Minserk Cheong, Kwang-Deog Jung, Chang Soo Kim, Deb Kumar Mukherjee, Honggon Kim, and Ki Young Lee
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chemistry.chemical_compound ,Chemistry ,Ionic liquid ,Inorganic chemistry ,medicine ,Halide ,General Chemistry ,Acetonitrile ,Chloride ,medicine.drug ,Ion - Abstract
Halide anion effects of ILs were investigated using eight IL samples: [BMIm]Cl (1-butyl-3-methylimidazolium chloride; Aldrich 97%), [BMIm]Br (Aldrich, 97%), [BMIm]I (prepared), [EMIm]Cl (1-ethyl-3-methylimidazolium chloride; c-tri Korea, 98%), [HMIm]Cl (1-hexyl-3-methylimidazolium chloride; c-tri Korea, 98%), [OMIm]Cl (1-octyl-3-methylimidazolium chlo-ride; c-tri Korea, 98%), [BMpyri]Cl (1-butyl-4-methylpyridini-um chloride; prepared, 98%) and [BMpyrr]Cl (1-butyl-4-methyl-pyrrolidinium chloride; prepared, 98%).For the preparation of [BMIm]I, [BMIm]Cl (0.05 mol) was dissolved in acetonitrile. NaI (0.05 mol) was added in the [BMIm]Cl solution, which was stirred at room temperature for 48 h. Then, the solution was filtered to remove KCl, and dried with MgSO more...
- Published
- 2010
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33. Cellulose triacetate-based polymer gel electrolytes
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Honggon Kim, Seul Lee, Byoung Sung Ahn, Jung Min Lee, Dinh Quan Nguyen, Hoon Sik Kim, and Hyunjoo Lee
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Polymers and Plastics ,chemistry.chemical_element ,General Chemistry ,Lithium battery ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Cellulose triacetate ,Differential scanning calorimetry ,chemistry ,Polymer chemistry ,Ionic liquid ,Materials Chemistry ,Ionic conductivity ,Lithium ,Thermal stability ,cardiovascular diseases ,Imide - Abstract
New composite polymer gels were obtained from cellulose triacetate (CTA), N-methyl-N′-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr1,3TFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Analysis by differential scanning calorimeter and scanning electron microscope showed that the ionic gel consisting of CTA, Pyr1,3TFSI, and LiTFSI formed a completely homogeneous phase at the molar ratio of CTA/Pyr1,3TFSI/LiTFSI = 1/3/1.5. The ionic conductivity of the polymer gel was significantly enhanced by the presence of LiTFSI. FTIR study strongly implies that the interaction of lithium ion with the carbonyl group of CTA could be responsible for the increase in conductivity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 more...
- Published
- 2010
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34. An experimental study on the performance of a zinc air fuel cell with inexpensive metal oxide catalysts and porous organic polymer separators
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Prabal Sapkota and Honggon Kim
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Materials science ,General Chemical Engineering ,Inorganic chemistry ,Oxide ,Separator (oil production) ,chemistry.chemical_element ,Electrolyte ,Zinc ,Engineering plastic ,Alkali metal ,Durability ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Porosity - Abstract
A zinc air fuel cell (ZAFC) of taper-end structure was designed and manufactured with a polyamide-base engineering plastic. An air cathode with multiple layers of blended inexpensive metal oxides, MnO2 and CeO2, showed a remarkably stable electricity-generating performance even at high current density. A cheap thin Nylon filter was found as a potential candidate for the separator in ZAFC because of its high stability and durability in the alkali electrolyte and proper pore size. more...
- Published
- 2010
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35. Solubility of CO2 in dialkylimidazolium dialkylphosphate ionic liquids
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Byoung Koun Min, Honggon Kim, Dinh Quan Nguyen, Hoon Sik Kim, Je Eun Kang, Jelliarko Palgunadi, Sang Deuk Lee, and Jin Hyung Kim
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chemistry.chemical_classification ,Chemistry ,Inorganic chemistry ,Enthalpy ,Solvation ,Condensed Matter Physics ,Gibbs free energy ,chemistry.chemical_compound ,symbols.namesake ,Ionic liquid ,symbols ,Physical and Theoretical Chemistry ,Solubility ,Imide ,Instrumentation ,Dissolution ,Alkyl - Abstract
The solubility of carbon dioxide in room temperature ionic liquids (RTILs), dialkylimidazolium dialkylphosphates, was measured at 313–333 K and at pressures close to atmospheric pressure, from which Henry's law coefficients, standard Gibbs free energy, enthalpy, and entropy changes of solvation were derived. The CO2 solubility in the dialkylimidazolium dialkylphosphate was found to increase with increasing chain length of the alkyl groups on the cation and/or the anion as was similarly found in other RTILs. Among various dialkylimidazolium dialkylphosphates tested, 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][Et2PO4]) and 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][Bu2PO4]) exhibited the comparable or better capability of dissolving CO2 in comparison with that of [BMIM][BF4], but their absorption capacities were still lower than that of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). more...
- Published
- 2009
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36. Fluorine-Free Imidazolium-Based Ionic Liquids with a Phosphorous-Containing Anion as Potential CO2Absorbents
- Author
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Minserk Cheong, Honggon Kim, Je Eun Kang, Hoon Sik Kim, Hyunjoo Lee, and Jelliarko Palgunadi
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chemistry.chemical_compound ,Hildebrand solubility parameter ,Tetrafluoroborate ,Molar volume ,chemistry ,Ionic liquid ,Inorganic chemistry ,Organic chemistry ,Fugacity ,General Chemistry ,Solubility ,Imide ,Mole fraction - Abstract
Solubilities of carbon dioxide (CO2) in a series of fluorine-free room temperature ionic liquids (RTILs), dialkylimi- dazolium dialkylphosphates and dialkylimidazolium alkylphosphites, were measured at 313∼333 K and pressures up to 5 MPa. Henry's law coefficients as the solubility parameter of CO2 in RTILs were derived from the isotherm of fugacity versus CO2 mole fraction. The CO2 solubility in a phosphorus-containing RTIL was found to increase with the increasing molar volume of the RTIL. In general, dialkylimidazolium dialkylphosphate exhibited higher absorption capacity than dialkylimidazolium alkylphosphite as long as the RTILs possess an identical cation. Among RTILs tested, 1-butyl-3-methylimidazolium dibutylphosphate (BMIM)(Bu2PO4) and 1-butyl-3-methylimidazolium butylphosphite (BMIM)(BuHPO3) exhibited similar Henry's law coefficients to 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ((BMIM)(Tf2N)) and 1-butyl-3-methylimidazolium tetrafluoroborate ((BMIM)(BF4)), respectively. The Krichevsky-Kasarnovsky equation was employed to derive the CO2 solubility parameter (Henry's law coefficient) from the solubility data measured at elevated pressures. more...
- Published
- 2009
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37. Zinc–air fuel cell, a potential candidate for alternative energy
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Honggon Kim and Prabal Sapkota
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business.industry ,General Chemical Engineering ,chemistry.chemical_element ,Potential candidate ,Precious metal ,Zinc ,Electrolyte ,Commercialization ,Renewable energy ,chemistry ,Alternative energy ,Environmental science ,Electricity ,Process engineering ,business - Abstract
A zinc–air fuel cell (ZAFC), which generates electricity by the reaction between oxygen and zinc pallets in a liquid alkaline electrolyte, is a potential candidate for an alternative energy generator. It is efficient, completely renewable, and cheap in fabrication because precious metal catalysts are not necessary. In addition, it is environmentally benign because of producing solely recyclable zinc oxide without gas emission. It is applicable to portable, mobile, stationary, and military purposes. In spite of its high potential as an alternative power source, it is yet in a preliminary stage of commercialization because of a few uncertainties remained. This paper reviews the present status of the ZAFC technology and the problems to be overcome for further advancement toward the potential next-generation alternative energy. more...
- Published
- 2009
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38. Facile One-Pot Synthesis of 1-Alkyl-3-polyfluoroalkyl Imidazolium Ionic Liquids
- Author
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Hoon Sik Kim, Dihn Quan Nguyen, Dong Sub Kim, Honggon Kim, Debby Natalia, Dong Jin Suh, and Hyunjoo Lee
- Subjects
chemistry.chemical_classification ,chemistry.chemical_compound ,chemistry ,Organic Chemistry ,Ionic liquid ,One-pot synthesis ,Polymer chemistry ,Fluorine ,chemistry.chemical_element ,Hydroamination ,Alkyl - Abstract
Imidazolium-based ionic liquids bearing a polyfluorinated alkylgroup on the cation were efficiently synthesized in excellent yieldsand selectivities from the one-pot reaction of a fluoroolefin with [1-alkyl-3 H-imidazolium]X, where X = Cl,NO 3 , CF 3 CO 2 , BF 4 or(CF 3 SO 2 ) 2 N, formed in situ fromthe interaction of an alkylimidazole with an acid, HX. more...
- Published
- 2009
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39. Use of ionic liquids as absorbents to separate SO2 in SO2/O2 in thermochemical processes to produce hydrogen
- Author
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Chang Soo Kim, Kwang Ho Song, Honggon Kim, Kwang-Deog Jung, Gyeongtaek Gong, and Ki Yong Lee
- Subjects
Hydrogen ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Sulfuric acid ,Condensed Matter Physics ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Desorption ,Ionic liquid ,Thermal stability ,Thermochemical cycle ,Solubility ,Absorption (chemistry) - Abstract
In the thermochemical cycles such as the SI (sulfur–iodine) cycle, the Westinghouse process, and Ispra Mark 13 process, SO2 needs to be separated and purified to enhance system efficiency. As novel absorbents with non-volatility, thermal stability and high SO2 absorption capability, the characteristics of ionic liquids (ILs) as SO2 absorbents were investigated to separate SO2 in SO2/O2 gaseous mixtures from the sulfuric acid decomposer. SO2 absorption and desorption experiments showed that SO2 solubility and absorption rate in ILs were influenced mainly by anions of ILs. [BMIm][Cl] and [BMIm][OAc] (1.40–1.69 SO2 gmol/ILs gmol) showed the highest SO2 solubility among the tested ILs at 50 °C and 0.67 atm P SO 2 . Interestingly, [BMIm][OAc] showed irreversibility in the cycle of absorption and desorption. [BMIm][MeSO4] showed moderate SO2 solubility and good reversible cycles of absorption and desorption. The dependency of temperature and pressure on SO2 solubility of [BMIm][MeSO4] was scrutinized. more...
- Published
- 2008
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40. Zwitterionic imidazolium compounds with high cathodic stability as additives for lithium battery electrolytes
- Author
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Hyunjoo Lee, Minserk Cheong, Je Seung Lee, Dinh Quan Nguyen, Honggon Kim, Hoon Sik Kim, Eun Hee Jeon, and Hyun Woo Bae
- Subjects
Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Energy Engineering and Power Technology ,Electrolyte ,Electrochemistry ,Medicinal chemistry ,Lithium battery ,chemistry.chemical_compound ,chemistry ,Zwitterion ,Ionic liquid ,Carbonate ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Dimethyl carbonate ,Ethylene carbonate - Abstract
A series of imidazolium-based zwitterionic compounds having both a propylsulfonate group at 3-position and an ester group at 1- or 2-position are synthesized and their interactions with LiPF6 are investigated. FT-IR study and theoretical calculation using density functional theory show that the interactions of the zwitterionic compound with LiPF6 varies significantly with the location of the ester group on the imidazolium ring. The electrochemical stability of the imidazolium-based zwitterionic compound is significantly improved by introducing an ester group at the C-2 position of the imidazolium ring. Cycle performance tests show that the initial cell capacity remains almost unchanged up to 100 cycles at 1/2 C when 2.5 wt.% of 2-(acetoxymethy)-1-butylimidazolium-3-propylsulfonate is added to the model electrolyte consisting of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC) (EC/DMC/EMC = 1/1/1 v/v/v), whereas the capacity of the cell containing an unsubstituted or methyl-substituted imidazolium compound at the C-2 position, 1-(acetoxymethyl)imidazolium-3-propylsulfonate or 1-(acetoxymethyl)-2-methylimidazolium-3-propylsulfonate as an additive, starts to decrease rapidly just after a few cycles. more...
- Published
- 2008
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41. Fluoride-catalyzed hydroalkoxylation of hexafluoropropene with 2,2,2-trifluoroethanol
- Author
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Debby Natalia, Ji Hee Oh, Honggon Kim, Hyunjoo Lee, Dinh Quan Nguyen, and Hoon Sik Kim
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Hydrogen bond ,Organic Chemistry ,Inorganic chemistry ,Alkali metal ,Biochemistry ,Medicinal chemistry ,Dissociation (chemistry) ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,2,2,2-Trifluoroethanol ,Environmental Chemistry ,Physical and Theoretical Chemistry ,Selectivity ,Fluoride ,Hydroalkoxylation - Abstract
Trifluoroethoxylation of hexafluoropropene with 2,2,2-trifluoroethanol (TFE) were conducted using an alkali metal fluoride catalyst to produce CF 3 CHFCF 2 OCH 2 CF 3 . KF exhibited the highest yield and selectivity of CF 3 CHFCF 2 OCH 2 CF 3 , whereas LiF and NaF were inactive for the trifluoroethoxylation reaction. The same reaction also proceeded well in the presence of RbF or CsF, but yielded large amounts of olefinic and high molecular weight side products, implying that the size of alkali metal cation or the degree of MF dissociation plays an important role in determining the activity and the product composition. FT-IR and NMR experiments revealed that CsF interacts with TFE more strongly than KF through a hydrogen bonding. The experimental and spectroscopic results suggest that the degree of MF dissociation should be in the medium range for the selective production of CF 3 CHFCF 2 OCH 2 CF 3 in high yield and selectivity. more...
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- 2008
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42. One-pot synthesis of ethylene trithiocarbonate from ethylene carbonate
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Hyunjoo Lee, Minserk Cheong, Dinh Quan Nguyen, Je Seung Lee, Hoon Sik Kim, Honggon Kim, and Nan Hee Ko
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Ethylene ,Ethylene oxide ,Process Chemistry and Technology ,Inorganic chemistry ,Halide ,chemistry.chemical_element ,Catalysis ,chemistry.chemical_compound ,chemistry ,Lithium chloride ,Lithium ,Selectivity ,Ethylene carbonate ,Nuclear chemistry - Abstract
Ethylene trithiocarbonate (ETTC) was synthesized in good to excellent yields and selectivities from a one-pot catalytic reaction of ethylene carbonate (EC) and CS 2 in the presence of a lithium halide by using EC as a source of ethylene oxide (EO). The selectivity of ETTC was strongly affected by the rate of EC decomposition into EO and CO 2 . Lithium chloride, the least active catalyst for the EC decomposition, showed the highest yield and selectivity. more...
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- 2008
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43. Synthesis and Characterization of Quaternary Ammonium-based Ionic Liquids Containing an Alkyl Carbonate Group
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Dinh Quan Nguyen, Hyunjoo Lee, Hoon Sik Kim, Chang Soo Kim, Honggon Kim, Ji Hee Oh, and Seung Wook Kim
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chemistry.chemical_classification ,chemistry.chemical_compound ,Chemistry ,Ionic liquid ,Inorganic chemistry ,Carbonate ,Ionic conductivity ,Thermal stability ,Ammonium ,General Chemistry ,Electrolyte ,Electrochemistry ,Alkyl - Abstract
A series of quaternary ammonium-based ionic liquids (ILs) containing an alkyl carbonate group on the cation was first prepared and their physical and electrochemical properties including density, viscosity, thermal stability, electrochemical stability, and ionic conductivity were reported. These ILs exhibited wide electrochemical windows of at least 5.0 V and relatively high conductivities. In contrast to dialkyl-substituted ionic liquids, the ILs with an alkyl carbonate group on the cation showed much smaller drop in conductivities when mixed with a lithium salt, due to the interaction of lithium ions with carbonate groups. Upon interaction with a Li salt, the carbonyl stretching frequency of the carbonate group shifted to a lower frequency whereas the peak associated with C-O single bond moved to a higher frequency. more...
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- 2007
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44. Efficient Hydrogenation Catalysts of Ni or Pd on Nanoporous Carbon Workable in an Acidic Condition
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Ik-Mo Lee, Min Kang, Honggon Kim, Dong-Hwan Lee, and Ji Man Kim
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Steric effects ,Reaction mechanism ,Chemistry ,Inorganic chemistry ,Noyori asymmetric hydrogenation ,General Chemistry ,Catalysis ,Reaction rate ,Metal ,chemistry.chemical_compound ,Nanoporous carbon ,visual_art ,Trifluoroacetic acid ,visual_art.visual_art_medium ,Organic chemistry - Abstract
Efficient catalytic systems, where Ni or Pd is introduced in a supporting material of nanoporous carbon, have been developed for a liquid-phase hydrogenation of carboxylic acids and ketones at room temperature. It has been found that the catalysts reliably show high activities and selectivities for the hydrogenation to alcohols even in acidic conditions, and the catalytic activities depend on the preparative method of catalysts, the hydrogen pressure, the agitation rate, and the catalytic species. The hydrogenation of carboxylic acids and ketones clearly shows that the reaction rate is affected by the electronic and the steric effects, and a plausible reaction mechanism using metal hydrides as catalytic species is proposed. more...
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- 2007
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45. Preparation of novel ceramic membranes modified by mesoporous silica with 3-aminopropyltriethoxysilane (APTES) and its application to Cu2+ separation in the aqueous phase
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Jungwoo Moon, Honggon Kim, Taewook Kang, Seogil Oh, Surin Hong, and Jongheop Yi
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Aqueous solution ,Chemistry ,Metal ions in aqueous solution ,Inorganic chemistry ,Filtration and Separation ,Mesoporous silica ,Biochemistry ,Polyelectrolyte ,Mesoporous organosilica ,Ceramic membrane ,Membrane ,Chemical engineering ,General Materials Science ,Physical and Theoretical Chemistry ,Mesoporous material - Abstract
A chemically active inorganic membrane with an ordered mesoporous skin layer was used for separation of Cu 2+ in an aqueous solution. Mesoporous silica was deposited on the surface of a ceramic membrane using an anionic polyelectrolyte (poly(sodium 4-styrene sulfonate)) as an intermediate layer. A strong anionic polyelectrolyte was used to reduce electrostatic repulsion between the membrane surface and mesoporous silica under acidic (pH ≤ 1) conditions. Next, to provide the membrane and mesoporous skin layer with the ability to reject Cu 2+ ions, 3-aminopropyltriethoxysilane (APTES) was grafted onto the surface of the mesoporous skin layer. This modified membrane (CM-MA) was characterized by FE-SEM, TEM and FT-IR. The CM-MA showed a much higher total rejection value (87.08%) than that of the untreated membrane (6.09%). In addition, the CM-MA exhibited a highly selective separation capability for Cu 2+ ions in the presence of equimolar amounts of other metal ions (Ni 2+ , Pb 2+ ). more...
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- 2007
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46. Synthesis and H2 uptake of Cu2(OH)3Cl, Cu(OH)2 and CuO nanocrystal aggregate
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Sunghoon Park, Joong Beom Lee, Soon Chang Lee, Seung-Mok Lee, and Honggon Kim
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Range (particle radiation) ,Materials science ,Hydrogen ,Nanowire ,chemistry.chemical_element ,Nanotechnology ,General Chemistry ,Heterogeneous catalysis ,Catalysis ,Hydrothermal circulation ,Hydrogen storage ,chemistry ,Chemical engineering ,Nanocrystal - Abstract
Monodispersed Cu 2 (OH) 3 Cl nanoplatelets, Cu(OH) 2 nanowires, CuO nanoparticles and nanoribbons with a spherical morphology were synthesized using hydrothermal and heat-treatment reactions, and their H 2 storage characteristics were examined. The Cu 2 (OH) 3 Cl nanoplatelets particles formed immediately after mixing the reactant, which subsequently formed larger uniform spherical particles in the submicron range. This procedure highlights a practical strategy for producing spherical Cu(OH) 2 and CuO materials consisting of monodispersed nanocrystals. The spherical aggregates of Cu 2 (OH) 3 Cl nanoplatelets heat-treated at 473 K could reversibly store up to 2.35 wt.% H 2 at 38 bar and 293 K. more...
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- 2007
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47. A facile synthesis of fluorinated alkoxytrimethylsilanes using 1-methylimidazole as an acid scavenger
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Jin Hyung Kim, Hoon Sik Kim, Minserk Cheong, Bora Lee, Honggon Kim, Byoung Sung Ahn, and Hyunjoo Lee
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Cleaning agent ,Organic Chemistry ,Alcohol ,General Medicine ,Biochemistry ,Chloride ,Scavenger (chemistry) ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Ionic liquid ,Proton NMR ,medicine ,Environmental Chemistry ,Organic chemistry ,Physical and Theoretical Chemistry ,1-Methylimidazole ,medicine.drug - Abstract
Fluorinated alkoxytrimethylsilanes (RfCH2OSiMe3), potential candidates for the third-generation cleaning agents, were synthesized in high yields over 95% from the reaction of chlorotrimethylsilane and fluorinated alcohol (RfCH2OH) in the presence of 1-methylimidazole. Elemental and 1H NMR spectroscopic analysis showed that the reaction proceeds through the formation of an intermediate, 3-methyl-1-trimethylsilylimidazolium chloride. more...
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- 2007
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48. Multi-functional zwitterionic compounds as additives for lithium battery electrolytes
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Honggon Kim, Minserk Cheong, Je Seung Lee, Hoon Sik Kim, Hyunjoo Lee, Dinh Quan Nguyen, Bora Lee, and Jung Min Hwang
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Lithium tetrafluoroborate ,Electrolyte ,Electrochemistry ,Medicinal chemistry ,Lithium battery ,lcsh:Chemistry ,chemistry.chemical_compound ,Sulfonate ,chemistry ,lcsh:Industrial electrochemistry ,lcsh:QD1-999 ,Zwitterion ,Ionic liquid ,Functional group ,Organic chemistry ,lcsh:TP250-261 - Abstract
A series of multi-functional zwitterionic compounds having both ester and sulfonate groups were synthesized and their electrochemical properties were investigated. The effect of added zwitterionic compounds on the cycling performance of the cell containing 1 M LiPF6 in EC, DMC, and EMC (1/1/1 by vol.) was also examined. The cell capacity was not varied much at 1/5 C up to 50 cycles with the addition of either 2.25 wt% N-methylpyrrolidinium-N-(propyl sulfonate) (MePyS) or N-methylpiperidinium-N-(propyl sulfonate) (MePipS) as an additive, but dropped significantly at higher C rate of 1 C. Such a sharp decrease of the performance at higher C rate was not observed when MePyS or MePipS was replaced by N-(2-acetoxyethyl) pyrrolidinium-N-(propyl sulfonate) (EsPyS) or N-(2-acetoxyethyl) piperidinium-N-(propyl sulfonate) (EsPipS), implying the positive role of the ester functional group.FT-IR study clearly demonstrates that ester-containing zwitterionic compounds are able to interact with Li+ ions through both sulfonate and ester functional groups. Keywords: Zwitterionic compounds, Lithium battery, Ionic liquids, Cycling performance more...
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- 2007
49. Tailoring of Energy Levels in D-π-A Organic Dyes via Fluorination of Acceptor Units for Efficient Dye-Sensitized Solar Cells
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Min Jae Ko, Bongsoo Kim, Duck-Hyung Lee, Jin Young Kim, Hae Jung Son, Min Woo Lee, Jae-Yup Kim, Kyungkon Kim, Honggon Kim, and Doh Kwon Lee
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Photocurrent ,Multidisciplinary ,Materials science ,Band gap ,Energy conversion efficiency ,chemistry.chemical_element ,Photochemistry ,Acceptor ,Article ,Dye-sensitized solar cell ,chemistry.chemical_compound ,Cyanoacetic acid ,chemistry ,Fluorine ,HOMO/LUMO - Abstract
A molecular design is presented for tailoring the energy levels in D-π-A organic dyes through fluorination of their acceptor units, which is aimed at achieving efficient dye-sensitized solar cells (DSSCs). This is achieved by exploiting the chemical structure of common D-π-A organic dyes and incorporating one or two fluorine atoms at the ortho-positions of the cyanoacetic acid as additional acceptor units. As the number of incorporated fluorine atoms increases, the LUMO energy level of the organic dye is gradually lowered due to the electron-withdrawing effect of fluorine, which ultimately results in a gradual reduction of the HOMO-LUMO energy gap and an improvement in the spectral response. Systematic investigation of the effects of incorporating fluorine on the photovoltaic properties of DSSCs reveals an upshift in the conduction-band potential of the TiO2 electrode during impedance analysis; however, the incorporation of fluorine also results in an increased electron recombination rate, leading to a decrease in the open-circuit voltage (Voc). Despite this limitation, the conversion efficiency is gradually enhanced as the number of incorporated fluorine atoms is increased, which is attributed to the highly improved spectral response and photocurrent. more...
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- 2015
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50. Catalytic decomposition of sulfur trioxide on the binary metal oxide catalysts of Fe/Al and Fe/Ti
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Tae Ho Kim, Honggon Kim, Byung Gwon Lee, Kwang-Deog Jung, Hee Young Jeon, Chae-Ho Shin, Kwan-Young Lee, and Gyeongtaek Gong
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Hydrogen ,Process Chemistry and Technology ,Inorganic chemistry ,Oxide ,chemistry.chemical_element ,Decomposition ,Catalysis ,chemistry.chemical_compound ,chemistry ,Sulfur trioxide ,Water splitting ,Chemical decomposition ,Space velocity - Abstract
The iodine–sulfur (IS) cycle has been focused for hydrogen production by water splitting using a very high temperature nuclear reactor (VHTR) which is a high temperature heat source. The nuclear energy was absorbed at the temperature ranges of 750–900 °C by SO 3 decomposition reaction to SO 2 and O 2 in IS cycle. In this work, the activity of Fe/Al and Fe/Ti catalysts prepared by a co-precipitation was studied in an attempt to find some suitable catalysts for the decomposition of sulfur trioxide as the oxygen-generating reaction in the thermo-chemical water splitting process. The SO 3 decomposition was performed in the temperature range of 750–950 °C at a space velocity of 72,000 cm 3 /g cat. h in a fixed bed reactor. The catalytic activity of Fe/Al and Fe/Ti catalysts increased with an increase in Fe loadings, indicating that the Fe component should be active. The mechanism for the SO 3 decomposition on metal oxides can be described as follows: the metal sulfate formation (MO + SO 3 → MSO 4 ) and the decomposition of metal sulfate (MSO 4 → MO 2 + SO 2 and MO 2 → MO + 1/2O 2 ). more...
- Published
- 2006
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