1,721,013 research outputs found
Interaction of CO with atomically well-defined PtxRuy/Ru(0001) surface alloys
No full textThe interaction of CO with structurally well-defined PtxRuy surface alloys supported on Ru(0001) was investigated by thermal desorption spectroscopy and infrared reflection-absorption spectroscopy. The surface composition and the distribution of the surface atoms were controlled by high resolution scanning tunneling microscopy. On these surfaces, which have a nearly random distribution of the two surface species, the adsorption (and desorption) of CO is strongly modified compared to the pure elemental surfaces, by strain effects and electronic ligand effects. CO adsorbs exclusively in a linear configuration on Pt and Ru atoms for all surfaces investigated. The adsorption energy of CO is lowered on the alloy surfaces with respect to both Pt(111) and Ru(0001), similar as for pseudomorphic monolayer Pt films. For both Pt and Ru sites the adsorption strength decreases with increasing Pt concentration. (c) 2007 Elsevier B.V. All right
Reinforcing the Electrode/Electrolyte Interphases of Lithium Metal Batteries Employing Locally Concentrated Ionic Liquid Electrolytes
Get PDFLithium metal batteries (LMBs) with nickel-rich cathodes are promising candidates for next-generation high-energy-density batteries, but the lack of sufficiently protective electrode/electrolyte interphases (EEIs) limits their cyclability. Herein, trifluoromethoxybenzene is proposed as a cosolvent for locally concentrated ionic liquid electrolytes (LCILEs) to reinforce the EEIs. With a comparative study of a neat ionic liquid electrolyte (ILE) and three LCILEs employing fluorobenzene, trifluoromethylbenzene, or trifluoromethoxybenzene as cosolvents, it is revealed that the fluorinated groups tethered to the benzene ring of the cosolvents not only affect the electrolytes' ionic conductivity and fluidity, but also the EEIs' composition via adjusting the contribution of the 1-ethyl-3-methylimidazolium cation (Emim+) and bis(fluorosulfonyl)imide anion. Trifluoromethoxybenzene, as the optimal cosolvent, leads to a stable cycling of LMBs employing 5 mAh cm-2 lithium metal anodes (LMAs), 21 mg cm-2 LiNi0.8Co0.15Al0.05 (NCA) cathodes, and 4.2 mu L mAh-1 electrolytes for 150 cycles with a remarkable capacity retention of 71%, thanks to a solid electrolyte interphase rich in inorganic species on LMAs and, particularly, a uniform cathode/electrolyte interphase rich in Emim+-derived species on NCA cathodes. By contrast, the capacity retention under the same condition is only 16%, 46%, and 18% for the neat ILE and the LCILEs based on fluorobenzene and benzotrifluoride, respectively.A locally concentrated ionic liquid electrolyte based on trifluoromethoxybenzene cosolvent is proposed for lithium metal batteries with nickel-rich cathodes, through a comparative study of three fluorinated aromatic cosolvents. The generated solid electrolyte interphase rich in inorganic species on anodes and, particularly, a uniform cathode/electrolyte interphase rich in organic cation-derived species on cathodes enable stable cycling of Li/LiNi0.8Co0.15Al0.05O2 cells.imag
Metal–organic framework derived Fe7S8 nanoparticles embedded in heteroatom-doped carbon with Lithium and Sodium storage capability
Get PDFIron sulfides are promising materials for lithium- and sodium-ion batteries owing to their high theoretical capacity and widespread abundance. Herein, the performance of an iron sulfide-carbon composite, synthesized from a Fe-based metal–organic framework (Fe-MIL-88NH2) is reported. The material is composed of ultrafine Fe7S8 nanoparticles (<10 nm in diameter) embedded in a heteroatom (N, S, and O)-doped carbonaceous framework (Fe7S8@HD-C), and is obtained via a simple and efficient one-step sulfidation process. The Fe7S8@HD-C composite, investigated in diethylene glycol dimethyl ether-based electrolytes as anode material for lithium and sodium batteries, shows high reversible capacities (930 mAh g−1 for lithium and 675 mAh g−1 for sodium at 0.1 A g−1). In situ X-ray diffraction reveals an insertion reaction to occur in the first lithiation and sodiation steps, followed by conversion reactions. The composite electrodes show rather promising long-term cycling stability and rate capability for sodium storage in glyme electrolyte, while an improved rate capacity and long-term cycling stability (800 mAh g−1 after 300 cycles at 1 A g−1) for lithium can be achieved using conventional carbonates
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Impact of a PEO-based Interphase at the Negative Electrode of "Zero Excess" Lithium-Metal Batteries
No full text"Zero-excess" lithium-metal batteries represent a very promising next-generation battery concept, enabling extremely high energy densities. However, lithium metal deposition is often non-uniform and accompanied by severe side reactions with the electrolyte, limiting Coulombic efficiency and, thus, energy density and cycle life. To address this issue, we introduced a thin polymer-based artificial interphase at the negative electrode. The influence of this interphase on the lithium deposition, and generally the reactions occurring at the negative electrode, was evaluated by galvanostatic stripping/plating tests and a thorough ex situ analysis via scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), scanning photoemission microscopy (SPEM), and soft-X-ray absorption spectroscopy (soft-XAS). The results demonstrate that the introduction of such a polymer-based interlayer allows for more stable cycling and reduces dendritic lithium growth owing to the formation of a more homogeneous, thin, and fluorine-rich passivation layer
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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