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91.
Kinetic isotope effect (KIE) was used to study the rate-determining step for oxygen reduction reaction (ORR) on dispersed Pt/C electrocatalyst and polycrystalline Pt (Pt-poly). KIE is defined as the ratio of the kinetic current measured in protonated electrolyte versus deuterated electrolyte, with KIE values larger than one indicating proton participation in the rate-determining step. The effect of poisoning anions on the platinum rate determining step is investigated by assessing the KIE in perchloric (non-poisoning) and sulfuric acid-based electrolytes. The kinetics currents were calculated using the Koutechy-Levich and Tafel analysis. A KIE of 1 was observed for Pt/C (with a 40 wt.% Pt loading) and Pt-poly, thus indicating that, on 40 wt. % Pt/C and Pt-poly, the rate determining step is proton independent.  相似文献   
92.
Platinum group metal–free (PGM-free) catalysts are promising candidates to catalyze the oxygen reduction reaction in polymer electrolyte fuel cells (PEFCs). Because of their low activity, larger loadings are used resulting in thicker catalyst layers. Transport, particularly water management, thereby becomes a more prominent performance factor. Currently, very few works attempted to understand water management in PGM-free catalyst layers, mainly because of other challenges that had to be overcome first, such as enhancing their activity and durability. The field has also been active in a hypothesis discussion of micropores flooding that led to the belief that poor stability of the PEFC performance is linked to active sites flooding within the micropores. We present here an overview of recent advances in understanding water management in the PGM-free catalyst layer for oxygen reduction reaction in PEFCs and provide an opinion on design guidance in optimizing catalyst layers to avoid flooding.  相似文献   
93.
The synthesis of novel pyrrolo[1,2-a]azolo-(azino-)[c]quinazolines by tandem reaction of 2-(azolyl-(azinyl-))anilines with oxocarboxylic acids was described in this article. The mechanism of obtained compounds formation was proposed, and the intermediate of the heterocyclization has been isolated and characterized. The IR-, 1H and 13C NMR-, chromato-mass spectra of synthesized compounds were studied for estimation of their structure and spectral patterns features. The molecular structure of the obtained compounds was additionally proved by X-ray diffraction method.  相似文献   
94.
X-ray imaging techniques are powerful tools for understanding morphology, transport and even reactions within the electrochemical energy systems. Transmission X-ray microscopy (TXM) and X-ray computed tomography (CT) have been widely used in ex-situ studies to probe morphology of electrochemical energy materials. Emerging operando studies highlight the possibility of imaging energy materials and devices under realistic operating conditions. We present an overview of recent advances in the X-ray CT methods with application to fuel cells, batteries and other energy technologies, and describe how the information obtained with multimodal imaging is used within the multi-scale computational models. Overall, the progress in imaging outran the modeling progress, and current models are limited in their utility to incorporate vast amount of multimodal image data.  相似文献   
95.
96.
Despite significant progress in conformational analysis of cyclic molecules, the number of computational studies is still limited while most of that available in the literature data have been obtained long time ago with outdated methods. In present research, we have studied temperature driven conformational changes of the furan ring at three different temperatures. Additionally, the effect of deuteration on the ring dynamics is discussed; in addition, the aromaticity indices following the Bird and HOMA schemes are computed along all trajectories. Our ab initio molecular dynamic simulations revealed that deuteration has changed the furan ring dynamics and the obvious consequences; in addition, the shape and size of molecule are expected to be different.  相似文献   
97.
A general approach to a new generation of spirocyclic molecules – oxa-spirocycles – was developed. The key synthetic step was iodocyclization. More than 150 oxa-spirocyclic compounds were prepared. Incorporation of an oxygen atom into the spirocyclic unit dramatically improved water solubility (by up to 40 times) and lowered lipophilicity. More potent oxa-spirocyclic analogues of antihypertensive drug terazosin were synthesized and studied in vivo.

A general practical approach to a new generation of spirocyclic molecules – oxa-spirocycles – is developed.  相似文献   
98.
The treatment of InCl3 with MOCH(CF3)2 (M = Li, Na, K) in a 1:6 stoichiometry, followed by recrystallisation results in the formation of the bimetallic “ate” complexes [Na3In(OCH(CF3)2)6(THF)3] (2) and [Li3In(OCH(CF3)2)6(THF)3] (5) from hexane, and [K3In(OCH(CF3)2)6]n (4) from a THF and toluene mixture. If a 1:3 stoichiometry is used chloride containing compounds [Na2InCl(OCH(CF3)2)4(THF)4] (1) and [KInCl2 (OCH(CF3)2)2(THF)3]n · THF (3) are obtained on recrystallisation from hexane. Treatment of GaCl3 with 6 equivalents of LiOC(CH3)2CF3 gives [LiGa(OC(CH3)2CF3)4(THF)2] (6) on recrystallisation from hexane. The protolysis reaction between In(N(SiMe3)2)3, formed in situ from (Me3Si)2NH, nBuLi and Incl3, and HOCH(CH3)CF3 results in isolation of [LiIn(OCH(CH3)CF3)3Bu]2 (7) from hexane. The structures of 2, 4, and 5 all contain the tetranuclear core InO6M3. Compounds 1 and 3 have residual chloride; 1 is a trinuclear species with two THF ligands per Na, while 3 is a linear polymer. Compound 6 has a GaO2Li four-membered parallelogram at its core. Complex 7 has a tetranuclear In2O6Li2 core and an unexpected nBu group on the In atoms. The coordination spheres of the alkali metals in 1-6 include solvated THF while 1-5 display additional close M?F interactions.  相似文献   
99.
100.
The biological mediation of mineral formation (biomineralization) is realized through diverse organic macromolecules that guide this process in a spatial and temporal manner. Although the role of these molecules in biomineralization is being gradually revealed, the molecular basis of their regulatory function is still poorly understood. In this study, the incorporation and distribution of the model intrinsically disordered starmaker-like (Stm-l) protein, which is active in fish otoliths biomineralization, within calcium carbonate crystals, is revealed. Stm-l promotes crystal nucleation and anisotropic tailoring of crystal morphology. Intracrystalline incorporation of Stm-l protein unexpectedly results in shrinkage (and not expansion, as commonly described in biomineral and bioinspired crystals) of the crystal lattice volume, which is described herein, for the first time, for bioinspired mineralization. A ring pattern was observed in crystals grown for 48 h; this was composed of a protein-enriched region flanked by protein-depleted regions. It can be explained as a result of the Ostwald-like ripening process and intrinsic properties of Stm-l, and bears some analogy to the daily growth layers of the otolith.  相似文献   
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