1,721,043 research outputs found
Optimizing noble metals exploitation in water oxidation catalysis by their incorporation in layered double hydroxides
No full textWater oxidation (WO) is considered the ideal process for the generation of electrons and protons necessary for the production of sustainable fuels. The unfavorable kinetics of this reaction requires the development of highly efficient catalysts (WOCs). The most promising performance has been obtained with noble metal based systems, which however pose challenges for the careful exploitation of these precious elements. In this Review, one of the most promising strategies for the development of WOCs in a ‘noble metal atom economy’ fashion is described, that is, the incorporation of these metals in layered double hydroxides (LDHs) of earth abundant elements. A rapidly raising number of studies demonstrate that excellent catalytic activity and durability can be obtained by following this strategy. The strong electronic coupling between noble metal nanoparticles or single atoms and the LDHs matrix is typically responsible for such intriguing results. Interestingly, noble metal incorporation as low as 1 wt% allows to boost the catalytic performance of intrinsically active systems like NiFe-LDHs, but also to activate otherwise inert materials like ZnAl-LDHs
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
Poly(3,4-ethylenedioxythiophene) in dye-sensitized solar cells: toward solid-state and platinum-free photovoltaics
No full textDye-sensitized solar cells (DSSCs) have become a strong reality in the field of hybrid photovoltaics. Their ability to operate in diffused light conditions and the possibility of fabrication of modules bearing different colors make these cells attractive for different applications, for example, wearable electronics, building integration, etc. This review focuses on one of the compounds rather often studied for DSSCs, namely, poly(3,4-ethylenedioxythiophene) (PEDOT). It has been introduced both as a substitute for liquid electrolytes, in order to facilitate cells fabrication and increase their durability, and as an alternative to platinum for counter electrodes. The literature counts many studies on PEDOT and this manuscript collects them following a classification criterion based on applications, functionalization/doping strategies, and deposition methods. In addition to comparing the performance obtained for PEDOT-based systems with those of traditional cells (i.e., assembled with liquid iodine-based electrolytes and platinum cathodes), the manuscript also offers a brief analysis of costs and sustainability aspects, built up on experimental data found in the literature; this latter is expected to constitute a precious resource to catalyze the attention of the scientific community on relevant and preliminary aspects when figuring out the industrial scalability of newly proposed cell components
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
Recent advances in eco-friendly and cost-effective materials towards sustainable dye-sensitized solar cells
No full textDye-sensitized solar cells (DSSCs), as emerging photovoltaic technology, have been thoroughly and extensively investigated in the last three decades. Since their first appearance in 1991, DSSCs have gained increasing attention and have been classified as feasible alternatives to conventional photovoltaic devices due to their numerous advantages, such as cheap and simple preparation methods, the possibility of being integrated in buildings and astonishing performances under indoor and diffuse illumination conditions. Photoconversion efficiencies of up to 14% and 8% have been obtained for lab-scale devices and modules, respectively. Albeit the efforts made, these values seem arduous to be outdone, at least under simulated solar radiation. Nevertheless, recent lab-scale systems have demonstrated photoconversion efficiencies of up to 33% under indoor illumination (i.e. 1000 lux) leading to an actual Renaissance (or Revival) of these devices. It is worth mentioning that scientists in this field are developing innovative materials aiming at long-term and efficient devices, being the concept of sustainability often set apart. However, in light of effective commercialization of this technology, stability, efficiency and sustainability should be considered as the essential keywords. Nowadays, DSSCs are finding a "new way back"towards sustainability and rather a huge number of reports have focused on the preparation of green and cost-effective materials to replace the standard ones. In this scenario, the present review aims to give an overview of the most adopted strategies to enhance the sustainability of materials in classical DSSC components (e.g. sensitizer, redox couple, electrolyte and counter-electrode), including smart synthesis and deposition procedures, which currently represent utmost important topics in the scientific community. This journal i
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
Unveiling commercial carbon electrodes for potassium batteries: an in-depth characterization
No full textPotassium-ion batteries (PIBs) are witnessing during the last years an unprecedent interest from the research community. This trend is given by PIBs potential in replacing Li-ion batteries for stationary energy storage plants. Indeed, potassium is abundant on Earth (2.09 wt%), evenly distributed and characterized by a very low standard equilibrium potential (-2.93 V vs. SHE with respect to -3.09 V vs. SHE of Li+/Li) and Lewis acidity (smaller solvated ions and thus faster conduction).
Nevertheless, potassium provides ions the radius of which almost doubles the lithium one, i.e. 1.38 Å vs. 0.76 Å, respectively. This divergence requires a different kind of anode with respect to Li-ion batteries and, thus, a new approach in understanding their electrochemical storage performance is essential. Indeed, the confined space of a graphitic layered anode is not suitable for the accommodation of bigger K-ions as for the smaller Li-ions. The mechanical stress caused by the K-ions diffusion leads to the pulverization of graphitic materials and this shouts the need for anodes with disordered amorphous phases. Their high densitiy of voids and defects provides a high surface area, where K-ions can deposit and be adsorbed storing energy. For this reason, soft and hard amorphous carbon represent the most performing anode materials for PIBs, showing better life cycle, stability and capacity provided. Anyway, their storage mechanism is very different with respect to their Li-graphite system counterpart, where most of the electrochemical capacity is ascribed to the ion intercalation between the graphene layers, and only a limited amount is due to ion adsorption on graphite edges. Electrochemical storage on amorphous carbons occurs mainly as a Faradaic accumulation of ions on the carbon surface. The process is battery-like, nonetheless they behave as a capacitor, and so they are called pseudocapacitive materials.
In this work, commercial carbon materials, known as Super P, C65 and C45, and their pseudocapacitive behaviour are in-depth characterized through electrochemical and morphological analysis. Indeed, depending on their graphitization degree, cyclic voltammetry curve and voltage vs. specific capacity profiles can identify the voltage windows for both insertion and adsorption processes. These results can be confirmed by differential capacity curves, above all if extracted from increasing current data. The Cottrell statement relates the current response with the voltage scan rate and, from this relationship, Dunn’s method, Trasatti’s method, b-value measurement and diffusion coefficient spectra allow to identify and quantify the amount of pseudocapacitive behaviour of the material. To conclude, in-depth characterization allows us to better classify the electrochemical behaviour of these electrode materials, that is of vital significance when choosing the proper anode material for potassium-based batteries
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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