The Experts below are selected from a list of 702 Experts worldwide ranked by ideXlab platform
Masahiro Miura - One of the best experts on this subject based on the ideXlab platform.
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oxidative c h c h annulation of imidazopyridines and indazoles through rhodium catalyzed vinylene transfer
Organic Letters, 2020Co-Authors: Koushik Ghosh, Yuji Nishii, Masahiro MiuraAbstract:Transition-metal-catalyzed C–H activation followed by oxidative annulation with alkynes has been an efficient synthetic tool for the assembly of various polyaromatic scaffolds. Despite the substant...
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thioether directed peri selective c h arylation under rhodium catalysis synthesis of arene fused thioxanthenes
Organic Letters, 2019Co-Authors: Sanghun Moon, Yuji Nishii, Masahiro MiuraAbstract:A rhodium-catalyzed direct C–H arylation of naphthalene and anthracene was developed with the assistance of a thioether directing group. The reaction proceeded with exclusive peri-selectivity, and the series of coupling products were readily transformed into the corresponding sulfur-containing Polyaromatics. Charge-transport properties of the provided dithiapyrenes were evaluated by computational studies.
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Thioether-Directed Peri-Selective C–H Arylation under Rhodium Catalysis: Synthesis of Arene-Fused Thioxanthenes
2018Co-Authors: Sanghun Moon, Yuji Nishii, Masahiro MiuraAbstract:A rhodium-catalyzed direct C–H arylation of naphthalene and anthracene was developed with the assistance of a thioether directing group. The reaction proceeded with exclusive peri-selectivity, and the series of coupling products were readily transformed into the corresponding sulfur-containing Polyaromatics. Charge-transport properties of the provided dithiapyrenes were evaluated by computational studies
Yu Seung Kim - One of the best experts on this subject based on the ideXlab platform.
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adsorption of polyaromatic backbone impacts the performance of anion exchange membrane fuel cells
Chemistry of Materials, 2019Co-Authors: Ivana Matanovic, Eun Joo Park, Chulsung Bae, Sandip Maurya, Jong Yeob Jeon, Yu Seung KimAbstract:The performance of anion exchange membrane fuel cells (AEMFCs) employing Pt or PtRu electrocatalyst and ionomers with different polyaromatic backbones is correlated with the density functional theo...
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rational design of polyaromatic ionomers for alkaline membrane fuel cells with 1 w cm 2 power density
Energy and Environmental Science, 2018Co-Authors: Sandip Maurya, Eun Joo Park, Chulsung Bae, Ivana Matanovic, Sangtaik Noh, Claudia Narvaez W Villarrubia, Ulises Martinez, Junyoung Han, Yu Seung KimAbstract:Alkaline membrane fuel cells (AMFCs) show great potential as alternative energy conversion devices to acidic proton exchange membrane fuel cells (PEMFCs). Over the last decade, there has been significant progress in the development of alkaline-stable polyaromatic materials for membrane separators and ionomeric binders for AMFCs. However, the AMFC performance using polyaromatic ionomers is generally poor, ca. a peak power density of <400 mW cm−2. Here, we report a rational design for polyaromatic ionomers which can minimize undesirable phenyl group interaction with hydrogen oxidation catalysts. The AMFC using a newly designed aryl ether-free poly(fluorene) ionomer exhibits a peak power density of 1.46 W cm−2, which is approaching that of Nafion-based PEMFCs. This study further discusses the remaining challenges of high-performing AMFCs.
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quaternized aryl ether free Polyaromatics for alkaline membrane fuel cells synthesis properties and performance a topical review
Journal of Materials Chemistry, 2018Co-Authors: Eun Joo Park, Yu Seung KimAbstract:Quaternized aryl ether-free Polyaromatics are an important family of polymer electrolytes for alkaline membrane fuel cells (AMFCs) due to their outstanding alkaline stability. In this review, state-of-the-art quaternized aryl ether-free Polyaromatics are discussed with respect to their synthesis and preparation. The mechanical and electrochemical properties and alkaline stability of the Polyaromatics that impact AMFC performance and durability are discussed in comparison with aryl ether-containing polyaromatic and polyolefinic electrolytes. Their performance in membrane electrode assemblies (MEAs) is discussed with emphasis on the area specific resistance and phenyl group adsorption on hydrogen oxidation catalysts. The AMFC performance of MEAs employing state-of-the-art aryl ether-free Polyaromatics is compared with those employing polyolefins and aryl ether-containing Polyaromatics. Finally, the limitations and outlook of quaternized aryl ether-free Polyaromatics are briefly summarized.
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anion conducting Polyaromatics having guanidine base
Meeting Abstracts, 2010Co-Authors: Dae Sik Kim, Yu Seung KimAbstract:A guanidine based poly(arylene ether sulfone)s (PAES-TMG) membrane was synthesized from the poly(arylene ether sulfone)s having activated fluorine group and tetramethylguanidine (TMG) without chloromethylation and/or bromination. The methylated PAES-TMG membranes do not have β-hydrogen, and TMG groups have high basicity (pKa = 13.6), which may reduce the potential of degradation due to E2 and SN2 reaction. The membrane showed the good stability in alkaline conditions (0.5M NaOH boiling temperature for 2hr, 80oC for 382hr). The OH- conductivities before and after NaOH test at 80oC for 382hr are 0.036 S/cm, and 0.023S/cm, respectively. The conductivity after exposure to ambient air is 0.019S/cm (σHCO3-) at 80oC.
Ivana Matanovic - One of the best experts on this subject based on the ideXlab platform.
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adsorption of polyaromatic backbone impacts the performance of anion exchange membrane fuel cells
Chemistry of Materials, 2019Co-Authors: Ivana Matanovic, Eun Joo Park, Chulsung Bae, Sandip Maurya, Jong Yeob Jeon, Yu Seung KimAbstract:The performance of anion exchange membrane fuel cells (AEMFCs) employing Pt or PtRu electrocatalyst and ionomers with different polyaromatic backbones is correlated with the density functional theo...
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rational design of polyaromatic ionomers for alkaline membrane fuel cells with 1 w cm 2 power density
Energy and Environmental Science, 2018Co-Authors: Sandip Maurya, Eun Joo Park, Chulsung Bae, Ivana Matanovic, Sangtaik Noh, Claudia Narvaez W Villarrubia, Ulises Martinez, Junyoung Han, Yu Seung KimAbstract:Alkaline membrane fuel cells (AMFCs) show great potential as alternative energy conversion devices to acidic proton exchange membrane fuel cells (PEMFCs). Over the last decade, there has been significant progress in the development of alkaline-stable polyaromatic materials for membrane separators and ionomeric binders for AMFCs. However, the AMFC performance using polyaromatic ionomers is generally poor, ca. a peak power density of <400 mW cm−2. Here, we report a rational design for polyaromatic ionomers which can minimize undesirable phenyl group interaction with hydrogen oxidation catalysts. The AMFC using a newly designed aryl ether-free poly(fluorene) ionomer exhibits a peak power density of 1.46 W cm−2, which is approaching that of Nafion-based PEMFCs. This study further discusses the remaining challenges of high-performing AMFCs.
Sandip Maurya - One of the best experts on this subject based on the ideXlab platform.
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adsorption of polyaromatic backbone impacts the performance of anion exchange membrane fuel cells
Chemistry of Materials, 2019Co-Authors: Ivana Matanovic, Eun Joo Park, Chulsung Bae, Sandip Maurya, Jong Yeob Jeon, Yu Seung KimAbstract:The performance of anion exchange membrane fuel cells (AEMFCs) employing Pt or PtRu electrocatalyst and ionomers with different polyaromatic backbones is correlated with the density functional theo...
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rational design of polyaromatic ionomers for alkaline membrane fuel cells with 1 w cm 2 power density
Energy and Environmental Science, 2018Co-Authors: Sandip Maurya, Eun Joo Park, Chulsung Bae, Ivana Matanovic, Sangtaik Noh, Claudia Narvaez W Villarrubia, Ulises Martinez, Junyoung Han, Yu Seung KimAbstract:Alkaline membrane fuel cells (AMFCs) show great potential as alternative energy conversion devices to acidic proton exchange membrane fuel cells (PEMFCs). Over the last decade, there has been significant progress in the development of alkaline-stable polyaromatic materials for membrane separators and ionomeric binders for AMFCs. However, the AMFC performance using polyaromatic ionomers is generally poor, ca. a peak power density of <400 mW cm−2. Here, we report a rational design for polyaromatic ionomers which can minimize undesirable phenyl group interaction with hydrogen oxidation catalysts. The AMFC using a newly designed aryl ether-free poly(fluorene) ionomer exhibits a peak power density of 1.46 W cm−2, which is approaching that of Nafion-based PEMFCs. This study further discusses the remaining challenges of high-performing AMFCs.
Kai Wang - One of the best experts on this subject based on the ideXlab platform.
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urban organic aerosol composition in eastern china differs from north to south molecular insight from a liquid chromatography orbitrap mass spectrometry study
Atmospheric Chemistry and Physics, 2019Co-Authors: Kai Wang, Rujin Huang, Martin Bruggemann, Yun Zhang, Lu Yang, Haiyan Ni, Meng Wang, Merete BildeAbstract:Abstract. Particulate air pollution in China is influencing human health, ecosystem and climate. However, the chemical composition of particulate aerosol, especially of the organic fraction, is still not well understood. In this study, particulate aerosol samples with a diameter l 2.5 μm (PM2.5) were collected in January 2014 in three cities located in Northeast, East and Southeast China, i.e., Changchun, Shanghai and Guangzhou, respectively. Organic aerosol (OA) in the PM2.5 samples was analyzed by ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution Orbitrap mass spectrometry in both negative mode (ESI−) and positive mode electrospray ionization (ESI+). After a non-target screening including molecular formula assignments, compounds were classified into five groups based on their elemental composition, i.e., CHO, CHON, CHN, CHOS and CHONS. The CHO, CHON and CHN compounds present the dominant signal abundances of 81–99.7 % in the mass spectra and the majority of these compounds were assigned to mono- and Polyaromatics, suggesting that anthropogenic emissions are a large source of urban OA in all three cities. However, the chemical characteristics of these compounds varied among different cities. The degree of aromaticity and the number of polyaromatic compounds were significantly higher in samples from Changchun, which could be attributed to the large emissions from residential heating (i.e., coal combustion) during winter time in Northeast China. Moreover, the ESI− analysis showed higher H / C and O / C ratios for organic compounds in Shanghai and Guangzhou compared to samples from Changchun, indicating that OA in lower latitude regions of China experiences more intense photochemical oxidation processes. The majority of sulfur-containing compounds (CHOS and CHONS) in all cities were assigned to aliphatic compounds with low degrees of unsaturation and aromaticity. Again, samples from Shanghai and Guangzhou exhibit a larger chemical similarity but largely differ from those from Changchun.