1,721,016 research outputs found
Probing the stability of SrIrO 3 during active water electrolysis via operando atomic force microscopy
No full textUsing atomically flat SrIrO 3 as a model electrocatalyst for water oxidation, we study the interplay between Sr 2+ leaching and perovskite dissolution at the nanometer scale through electrochemical atomic force microscopy.Mechanistic studies of oxide electrocatalysts for heterogeneous water oxidation have been primarily focused on understanding the origins of activity, with fewer studies addressing fundamental properties that influence stability. The main challenge is directly observing and quantifying local structural instability under operating conditions. In this work, we provide a dynamic view of the perovskite stability as a function of time and operational voltage using operando electrochemical atomic force microscopy (EC-AFM). Specifically, we study the degradation pathways of SrIrO 3 , a highly active electrocatalyst, during the oxygen evolution reaction (OER) by tracking the potential-dependent Sr leaching and perovskite dissolution at the nanometer scale. This material serves as a model system for degradation studies of perovskite AMO 3 oxides, exhibiting both A-cation leaching and transition metal (M) dissolution. We show that Sr leaching precedes perovskite dissolution by up to 0.8 V, leading to a wide voltage window of stability where water oxidation occurs on a Sr-depleted surface without significant corrosion. Moreover, we reveal that the stability of the perovskite surface is strongly influenced by the electrolytic environment and that corrosion rates differ dramatically as a function of dissolved Sr concentration. Ultimately, our study demonstrates that the overall stability of perovskite oxides during electrocatalysis can be substantially improved by suppressing A-site leaching.U.S. Department of Energy https://doi.org/10.13039/100000015Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659National Science Foundation https://doi.org/10.13039/10000000
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
Dewetting of Pt Nanoparticles Boosts Electrocatalytic Hydrogen Evolution Due to Electronic Metal-Support Interaction
Get PDFSolid-state dewetting is the heat-induced agglomeration of thin metal films into defined nanoparticles (NPs). Dewetted Pt nanoparticles are investigated on F-doped SnO2 (FTO) substrates as model binder-free electrodes for the hydrogen evolution reaction (HER). Dewetting of Pt films into particles exposes the FTO substrate and the metal/support (Pt-FTO) contact line. Despite the decrease in Pt electrochemical surface area (ECSA) upon dewetting, dewetted NPs show a >3-fold increase in ECSA-normalized HER activity compared to as-deposited nanocrystalline Pt films. Electrodes designed with dewetted Pt NPs of different sizes show that the HER activity does not only correlate with the ECSA but also increases with increasing the Pt-FTO contact line length. The smaller the NPs, the larger the Pt-FTO contact line, and the higher the activity. This effect is ascribed to electronic metal-support interaction (EMSI), due to electron transfer from FTO to Pt. It is proposed that EMSI effects alter the electronic structure of Pt sites near the Pt-FTO contact line, facilitating the H2 evolution kinetics. When NPs are a few nm-sized, a large mass fraction of Pt is affected by EMSI, resulting in a further increase of HER activity compared to NPs ≥10 nm despite the lower ECSA.</p
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
Carrier manipulation in graphene/ferroelectric hybrid structures
Get PDFThe combination of two novel classes of functional materials with exciting prospects for future nanoelectronic applications, i.e. carbon nanoelectronics and complex oxide thin film electronics, is expected to lead to a range of new phenomena being accessible for observation, scientific characterization and understanding, as well as for utilization in future electronic devices. This thesis reports significant advancement in the integration of two prominent representatives of these material classes - graphene and ferroelectric oxides.
First, the major road blocks complicating previous attempts to integrate graphene with ferroelectric oxides are identified. The hybrid devices fabricated so far suffered
from extrinsic hysteresis effects from adsorbed molecules screening any coupling between the graphene charge carriers and the ferroelectric polarization. The experimental methods utilized to overcome these challenges are introduced for device fabrication
and characterization.
The resulting graphene/PbZr0.2Ti0.8O3 hybrid structures presented here exhibit
bidirectional interdependency between the graphene doping level and the ferroelectric polarization. Using graphene-based electrodes, the polarization of the PbZr0.2Ti0.8O3
can be switched reliably and fast with low voltages, which in turn can change the doping
level in graphene channels. One of the most striking consequences of ferroelectriccpolarization switching dominating electron transport in graphene is the complete reversalcof the hysteresis direction in transistor devices. This reversible and permanent switching behavior can now be used in non-volatile ferroelectric graphene transistors.
To overcome the low on/off ratio of these devices, a utilization of complex domain structures underlying a graphene transistor channel is explored for novel carrier manipulation. Through the detailed characterization with Raman spectroscopy and scanning photocurrent measurements, the creation of potential steps in graphene at domain walls of the underlying ferroelectric is demonstrated. Carrier density modulations of approximately 5x 10^12 cm^-2 now provide a platform that offers graphene devices exhibiting potential steps which can be tuned from p+-p to p-n to n-n+ junctions through the application of a single gate for the entire channel area. This is particularly useful for the implementation and utilization of the exciting two-dimensional phenomena in graphene.Item withdrawn by Alexis Thompson ([email protected]) on 2013-04-18T14:44:02Z
Item was in collections:
University of Illinois Theses & Dissertations (ID: 1)
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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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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