1,721,034 research outputs found
Design of Li-O2 cells and study of the electrodes reactivity by means of a multi-technique approach
Full text linkThe PhD thesis work has been focused on aprotic Li-O2 cells assembled with different cathode materials in combination with the ether-based LiTFSI/TEGDME electrolyte. The performance of these promising energy storage systems have been investigated and related to the electrochemical and chemical processes at the triple O2/cathode/electrolyte interface and to the peculiar influence of each type of cathode material. These goals have been achieved by a powerful combination of techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The remarkable role of the TFSI- anion in the degradation process of a carbon-based cathode has been discussed in Chapter 4 on the basis of a post-mortem characterization of the positive electrode. Moreover, the fade of long-term stability of the cells has been related to the accumulation on the cathode surface of both insulating reaction products and byproducts, leading to the rise of overvoltages upon discharge and charge. A full electrochemical and chemical characterization of novel carbon-free Mn+-doped (Mn+=Cr3+ and Zn2+) NiCo2O4 nanomaterials grown on Ni foam (NCCr@Ni and NCZn@Ni) has been reported in Chapters 5 and 6. For the first time in the literature these materials have been tested as cathodes in Li-O2 cells and the beneficial effect of Cr(III)- and Zn(II)-doping of the NiCo2O4 spinel to boost the kinetics of both the ORR and the OER has been demonstrated. By means of in-house and synchrotron measurements the dopants role in the increase of the performance respect to the undoped material has been investigated. The preparation and characterization of novel composite Pd/PdO@NCCr@Ni cathodes made of Pd nanoparticles deposited on a nanostructured Cr(III)doped NiCo2O4 on Ni foam has been described in Chapter 7. The synergistic co-catalytic effect between the Pd NP and the doped nickel cobaltite has been proved to reduce both discharge and charge overvoltages and to improve the cell calendar life.
Overall, the general objectives of the PhD activity have been met, since three novel materials have been produced and demonstrated to be performing cathodes for Li-O2 cells. Moreover, this study allowed the acquisition of skills concerning laboratory practice and widely applicable electrochemical and chemical characterization techniques
Boosting Microbial Fuel Cell Performance by Combining with an External Supercapacitor: An Electrochemical Study
No full textAbstract Invited for this month's cover picture is the group of Dr. Francesca Soavi (Laboratory of Electrochemistry of Materials for Energetics, Department of Chemistry “Giacomo Ciamician”, University of Bologna). The cover picture shows a microbial fuel cell connected in parallel with a supercapacitor. Read the full text of the Article at 10.1002/celc.201901876
Bridging Electronics and Micro Energy Storage
No full textThe development of small, smart and remote objects requires microscale
components and energy autonomy. Activated carbon electrodes with high specific
surface areas, achieving high electrical double layer capacitances present an opportunity
to associate electronic components and energy storage. Transistors are a key
element in any integrated circuit and the use of carbon gate electrodes has proven
efficient to achieve low-voltage (sub-1 V) current modulation, reducing the energy
required to operate them. Furthermore, the monolithic integration of an ion-gated
transistor and a supercapacitor allowed to store and reuse up to 50% of the energy
used to switch on the transistor. This paves the path to low-power, durable and
autonomous devices able to function on small ambient energy harvesters and/or
energy storage units
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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