1,720,962 research outputs found
Engineering Cu2O Nanowire Surfaces for Photoelectrochemical Hydrogen Evolution Reaction
Get PDFCu2O is a narrow band gap material serving as an important candidate for photoelectrochemical hydrogen evolution reaction. However, the main challenge that hinders its practical exploitation is its poor photostability, due to its oxidation into CuO by photoexcited holes. Here, we thoroughly minimize the photo-oxidation of Cu2O nanowires by growing a thin layer of the TiO2 protective layer and an amorphous layer of the VOx cocatalyst using magnetron sputtering and atomic layer deposition, respectively. After optimization of the protective and the cocatalyst layers, the photoelectrode exhibits a current density of -2.46 mA/cm2 under simulated sunlight (100 mW/cm2) at 0.3 V versus reversible hydrogen electrode, and its performance is stable for an extended illumination time. The chemical stability and the good performance of the engineered photoelectrode demonstrate the potential of using earth-abundant materials as a light-harvesting device for solar hydrogen production
Sequential physical vapor deposition and chemical vapor deposition for the growth of In2O3-SnO2 radial and longitudinal heterojunctions
No full textHeterostructures of In2O3 and SnO2 were produced by sequential application of the physical- and chemical-vapor deposition techniques usually adopted for nanowire fabrication. In2O3 nanowires exhibit a single crystal body-centered cubic structure oriented along the [1 0 0] direction and grow epitaxially on alpha-sapphire substrate by means of a transport and condensation method assisted by Au nanoparticles. Nucleation and growth occurred via direct vapor solid (VS) mechanism competing with catalyst-mediated vapor-liquid-solid (VLS). SnO2 nanowires were obtained in a single crystal tetragonal (cassiterite) structure and oriented along the [1 0 1] direction, the growth being promoted by the gold particle at the apex of the In2O3 nanowires. The size of the catalyst thereby determines the main morphological features of SnO2 wires. CVD deposition allows precise control of the geometrical features of the heterojunction, also limiting detrimental nucleation of SnO2 on the lateral sides of In2O3 nanowires due to lower longitudinal growth rate. These results can help in improving the ability of finely tuning the morphological and structural properties of heterostructured oxide nanocrystals. (C) 2014 Elsevier B.V. All rights reserved
Cu/CGO cermet based electrodes for Symmetric and Reversible Solid Oxide Fuel Cells
Get PDFCu-based cermets suitable for electrodes in Symmetric and Reversible Solid Oxide Fuel Cells (SR-SOFCs) based on the Cerium Gadolinum Oxide (CGO) electrolyte were developed and successfully tested in the intermediate temperature range (600-800 degrees C). The Cu/CGO cermets were prepared by means of a self-combustion based citrate procedure and the effects of synthesis conditions were studied. Characterization of the Cu/CGO nanocomposites by XPS, XRD, SEM, TPR suggested that this procedure allows obtaining highly dispersed CuO on the cerium gadolinium oxide. Conversion higher than 80% was observed above 600 degrees C in methane total oxidation. Synthesis parameters affected both properties and catalytic performance. The behaviour under redox conditions was studied by operando high-energy XRD under oscillating H-2/O-2 feed. Reducing conditions converted CuO into Cu(0) passing through an intermediate Cu2O phase while increasing the conductivity and the reactivity. This structural modification was completely reversible. The high stability, reversibility, catalytic activity and electrochemical performance make these electrodes promising for SR-SOFCs. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
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
Hybrid thermal-field emission of ZnO nanowires
No full textThe electron emission properties of an array of ZnO nanowires were studied in the temperature
range of 300-473 K. An almost doubling of the current density at 473 K under an electric field of 8
V/lm (j(T¼473 K) ¼ 190 lA/cm2, j(T¼300 K)¼114 lA/cm2) was observed together with a reduction
of the turn-on field from 552 V/lm to 482 V/lm. Theoretical model that combines the thermal-field
emission for high electric field and the Schottky emission for the low field can satisfactorily
account for temperature dependence of current at low as well as at high applied bias. The obtained
effect is particularly appealing for the application in micro-gun for THz vacuum tubes
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
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
Electronic properties of chelating dicarbene palladium complexes: A combined electrochemical, NMR and XPS investigation
No full textA series of N-heterocyclic dicarbene palladium(II) complexes has been characterised combining different techniques (cyclic voltammetry, XPS and 13CNMR spectroscopy), in order to evaluate the influence of the dicarbene ligand on the electronic properties of the metal centre. The data obtained with the three techniques give relevant information, cyclic voltammetry appearing the most useful approach. In addition,the observed variations of the physico-chemical properties of the complexes confirm the possibility
of finely tuning the electronic properties of the palladium(II)centre by changing the characteristics of the dicarbene ligand (wingtip substituents, bridging group between the carbene units, type of heterocyclic ring)
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