排序方式: 共有12条查询结果,搜索用时 15 毫秒
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Jiazhan Li Hanguang Zhang Widitha Samarakoon Weitao Shan David A. Cullen Stavros Karakalos Mengjie Chen Daming Gu Karren L. More Guofeng Wang Zhenxing Feng Zhenbo Wang Gang Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19147-19156
FeN4 moieties embedded in partially graphitized carbon are the most efficient platinum group metal free active sites for the oxygen reduction reaction in acidic proton‐exchange membrane fuel cells. However, their formation mechanisms have remained elusive for decades because the Fe?N bond formation process always convolutes with uncontrolled carbonization and nitrogen doping during high‐temperature treatment. Here, we elucidate the FeN4 site formation mechanisms through hosting Fe ions into a nitrogen‐doped carbon followed by a controlled thermal activation. Among the studied hosts, the ZIF‐8‐derived nitrogen‐doped carbon is an ideal model with well‐defined nitrogen doping and porosity. This approach is able to deconvolute Fe?N bond formation from complex carbonization and nitrogen doping, which correlates Fe?N bond properties with the activity and stability of FeN4 sites as a function of the thermal activation temperature. 相似文献
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Maity PK Kainz QM Faisal S Rolfe A Samarakoon TB Basha FZ Reiser O Hanson PR 《Chemical communications (Cambridge, England)》2011,47(46):12524-12526
The utilization of a monomer-on-monomer (MoM) intramolecular Mitsunobu cyclization reaction employing norbornenyl-tagged (Nb-tagged) reagents is reported for the synthesis of benzofused thiadiazepine-dioxides. Facile purification was achieved via ring-opening metathesis (ROM) polymerization initiated by one of three metathesis catalyst methods: (i) free metathesis catalyst, (ii) surface-initiated catalyst-armed silica, or (iii) surface-initiated catalyst-armed Co/C magnetic nanoparticles. 相似文献
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Dinesh Kumar Rayabarapu Aihua Zhou Kyu Ok Jeon Thiwanka Samarakoon Alan Rolfe Hina Siddiqui Paul R. Hanson 《Tetrahedron》2009,65(16):3180-7773
The development of new methods to skeletally diverse sultams based on a central α-halo benzene sulfonamide building block is reported. Several salient features of this building block are utilized in multiple reaction pathways, including the Heck reaction, C- and O-arylation, Sonogashira-Pauson-Khand, Sonogashira-intramolecular hydroamination, and domino aza-Michael-Heck for the generation of five-, six-, and seven-membered benzofused bicyclic and tricyclic sultams. 相似文献
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Samarakoon TB Loh JK Rolfe A Le LS Yoon SY Lushington GH Hanson PR 《Organic letters》2011,13(19):5148-5151
A reaction pairing strategy centered on utilization of a reaction triad (sulfonylation, S(N)Ar addition and Mitsunobu alkylation) generating skeletally diverse, tricyclic and bicyclic benzofused sultams is reported. Pairing sulfonylation and S(N)Ar reactions yields bridged, tricyclic and bicyclic benzofused sultams. Application of the Mitsunobu reaction in a sulfonylation-Mitsunobu-S(N)Ar pairing allows access to benzthiazocine-1,1-dioxides, while a simple change in the order of pairing to sulfonylation-S(N)Ar-Mitsunobu affords structurally different, bridged tricyclic benzofused sultams. 相似文献
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Fractal groups (also called self-similar groups) is the class of groups discovered by the first author in the 1980s with the purpose of solving some famous problems in mathematics, including the question of raising to von Neumann about non-elementary amenability (in the association with studies around the Banach-Tarski Paradox) and John Milnor’s question on the existence of groups of intermediate growth between polynomial and exponential. Fractal groups arise in various fields of mathematics, including the theory of random walks, holomorphic dynamics, automata theory, operator algebras, etc. They have relations to the theory of chaos, quasi-crystals, fractals, and random Schrödinger operators. One important development is the relation of fractal groups to multi-dimensional dynamics, the theory of joint spectrum of pencil of operators, and the spectral theory of Laplace operator on graphs. This paper gives a quick access to these topics, provides calculation and analysis of multi-dimensional rational maps arising via the Schur complement in some important examples, including the first group of intermediate growth and its overgroup, contains a discussion of the dichotomy “integrable-chaotic” in the considered model, and suggests a possible probabilistic approach to studying the discussed problems. 相似文献
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Maity PK Rolfe A Samarakoon TB Faisal S Kurtz RD Long TR Schätz A Flynn DL Grass RN Stark WJ Reiser O Hanson PR 《Organic letters》2011,13(1):8-10
A monomer-on-monomer (MoM) Mitsunobu reaction utilizing norbornenyl-tagged (Nb-tagged) reagents is reported, whereby purification was rapidly achieved by employing ring-opening metathesis polymerization, which was initiated by any of three methods utilizing Grubbs catalyst: (i) free catalyst in solution, (ii) surface-initiated catalyst-armed silica, or (iii) surface-initiated catalyst-armed Co/C magnetic nanoparticles. 相似文献
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Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 C, autogenous pressure, batch reactor). The initial surface-specific activities for ethylene glycol reforming were in a similar range but decreased in the order of Pt (15.5 h1 ) >Co(13.0 h1 ) >Ni(5.2 h1 ) while the Cu catalyst only showed low dehydrogenation activity. The hydrogen molar selectivity decreased in the order of Pt (53%)>Co(21%)>Ni (15%) as a result of the production of methane over the latter two catalysts. Over the Co catalyst acids were formed in the liquid phase while alcohols were formed over Ni and Pt. Due to the low pH of the reaction mixture, especially in the case of Co (as a result of the formed acids), significant cobalt leaching occurs which resulted in a rapid deactivation of this catalyst. Investigations of the spent catalysts with various techniques showed that metal particle growth is responsible for the deactivation of the Pt and Ni catalysts. In addition, coking might also contribute to the deactivation of the Ni catalyst. 相似文献
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