1,721,021 research outputs found
The influence of organizational culture as moderator between person-organization (P-O) fit and work attitudes
No full textGreen synthesis of a redox-active riboflavin-integrated Ni-MOF and its versatile electrocatalytic applications towards oxygen evolution and reduction, and HMF oxidation reactions
No full textThe post-synthetic modification (PSM) of metal-organic frameworks (MOFs) with redox-active molecules under mild conditions is a highly challenging approach to modify the inherent properties of MOFs without altering their crystallinity and other characteristics. Here, we prepared a single crystal Ni-MOF with a two-dimensional rod-like morphology. Furthermore, we utilized the PSM technique to incorporate redox-active riboflavin (Rbf) in the Ni-MOF using a green and facile mechanochemical method under solvent-free conditions. The Rbf-doped Ni-MOF (Rbf-Ni-MOF) showed a 4-fold increase in conductivity compared to the pristine Ni-MOF. We employed the Rbf-Ni-MOF as a multifunctional electrocatalyst towards the oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and oxidation of 5-hydroxymethylfurfural (HMF). As an OER electrocatalyst, the Rbf-Ni-MOF delivered a high current density of 580 mA cm−2, which is around 26-fold greater than those of Rbf and the pristine Ni-MOF. The prep..
One-pot synthesis of ni0.05 ce0.95 o2−δ catalysts with nanocubes and nanorods morphology for CO2 methanation reaction and in operando drift analysis of intermediate species
Get PDFThe valorization of CO2 via renewable energy sources allows one to obtain carbon-neutral fuels through its hydrogenation, like methane. In this study, Ni0.05 Ce0.95 O2−δ catalysts were prepared using a simple one-pot hydrothermal method yielding nanorod and nanocube particles to be used for the methanation reaction. Samples were characterized by XRD, BET, TEM, H2-TPR, and H2-TPD experiments. The catalytic activity tests revealed that the best performing catalyst was Ni0.05 Ce0.95 O2−δ, with nanorod morphology, which gave a CO2 conversion of 40% with a selectivity of CH4 as high as 93%, operating at 325◦ C and a GHSV of 240,000 cm3 h−1 g−1 . However, the lower activation energy was found for Ni0.05 Ce0.95 O2−δ catalysts with nanocube morphology. Furthermore, an in operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis was performed flowing CO2:H2 or CO:H2 mixture, showing that the main reaction pathway, for the CO2 methanation, is the direct hydrogenation of formate intermediate
Phosphazene-Based Covalent Organic Polymer Decorated with NiCo2O4Nanocuboids as a Trifunctional Electrocatalyst: A Unique Replacement for the Conventional Electrocatalysts
No full textDeveloping nonprecious metal-based electrocatalysts to convert water into green fuels (H2 and O2) is key to address urgent climate and energy challenges. We have prepared an electrocatalyst by the immobilization of NiCo2O4 on a phosphazene-based covalent organic polymer (P-COP) through a facile hydrothermal method. The elemental composition of the P-COP showed the presence of a greater amount of heteroatoms N (6.62%) and P (5.62%) throughout the polymer support. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were utilized to determine the atomic structure of the nanocuboids, which depicted the formation of an inverse spinel structure. A NiCo2O4-P-COP-based electrode was simultaneously used for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), and it displayed a minimum overpotential of 270 and 130 mV (V vs RHE), respectively, at a current density of 10 mA cm-2. In addition, it acted as an oxygen reduction catalyst with a half-wave potential of 0.83 V (V vs RHE) and a maximum current density of 4.5 mA cm-2. The electrocatalytic activity is comparable with that of the commercially available Pt and RuO2 catalysts. The combined experimental and computational studies confirm that the catalytic centers formed through the interaction between the heteroatoms (N and P) in the phosphazene matrix and metal oxides (Co and Ni) play an important role in its improved durability and electrocatalytic activity
Production and size characterization of graphene
No full textGraphene, a 2D nanomaterial made of carbon, has gained interest in the scientific community since its discovery in 2004. Among other properties, graphene has excellent tensile strength, electrical and thermal conductivity and can be used as catalyst. Graphene has no shortage of applications, but large scale production methods are yet to be developed. LPE is a promising method, in which the layers that make up graphite are separated to produce graphene in a liquid medium. However, the flakes that are produced are polydispersed in size and thickness, which leads to the need for size selection. Current studies have achieved size selection with centrifugation. However, centrifugation has thus far been a trial and-error procedure, without understanding the underlying physics and statistics. This research focuses on creating a rational basis by combining experiments with simulations based on fluid dynamics and statistics. By combining results from simulations and experiments we are able to arrive at the size distributions of initial stock dispersion of graphene that was made from LPE. The simulations entail plate particle settling in a tube, where randomly generated polydisperse particles are randomly distributed in a tube. Stokes settling velocity is assumed for each particle. In parallel to this, we perform sedimentation experiments of stock dispersion at fixed relative centrifugal force (RCF) for different times. From the experiments we know the mass transfer from the supernatant to the sediment and the average thickness of the plates in the supernatant. Both these experimental results allow us to narrow the initial particle size distributions we assumed in the simulations. Thus we have developed a technique based on simple experiments and simulations that gives great insight into particle size distribution without having to perform tedious characterization such as AFM or TEM. Once the particle size distribution is known for a specific LPE protocol, it will allow the likes of both industry and academia to standardize graphene quality.<br/
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
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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