1,721,154 research outputs found
Strain engineering of dealloyed nanoporous cu for electrochemical CO(2) reduction
No full textThe electrochemical CO2 and CO reduction reaction (CO(2)RR) enables the recycling of greenhouse gases into valuable chemicals and fuels using renewable electricity. Among catalysts, Cu is unique in its ability to efficiently produce multi-carbon products, and nanoporous Cu (NPC) derived from brass dealloying has emerged as a promising candidate. However, fundamental understanding of both brass dealloying and CO₂RR mechanisms remains incomplete. This thesis advances knowledge in both areas.
In Chapter 3, we introduce CO Displacement, a new method to quantify active sites for CO(2)RR on Cu-based nanomaterials. Comparison with the conventional double-layer capacitance method across four nanostructured electrodes validated its accuracy. We confirm that electropolished Cu exhibits the highest intrinsic activity, and our findings suggest under-coordinated Cu atoms are the true active sites for CO₂RR. Chapter 4 explores NPC synthesis by chemical dealloying of Cu20Zn80 in 5 M H3PO4 at varied temperatures, yielding tuneable ligament sizes from tens of nanometres to micrometres. In situ synchrotron X-ray diffraction (XRD) and cryogenic-atom probe tomography (cryo-APT) reveal complex phase transformations during dealloying. We further propose a method based on XRD peak asymmetry to estimate under-coordinated atom density, expressed as ligament surface strain. Finally, electrochemical CO2 and CO reduction measurements using H-cell and electrochemical mass spectrometry (EC-MS) respectively demonstrate superior performance of NPC relative to polycrystalline Cu. A linear relationship between the CO intrinsic activity and ligament surface strain was found for CO2RR, and an optimal ligament surface strain value was also observed for the CO reduction of NPC on EC-MS. These results further suggest that under-coordinated Cu atoms are the active sites for CO(2)RR. Hence, this work establishes novel scientific methods for analysing nano-porous materials for electro-catalysis, with broad applicability to other nano-structured catalysts, as well as mechanistic insights into both dealloying of brass and electrochemical CO2 and CO reduction.Open Acces
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
Modeling Anion Poisoning during Oxygen Reduction on Pt Near-Surface Alloys
No full textElectrolyte effects play an important role in the activity of the oxygen reduction reaction (ORR) of Pt-based electrodes. Herein, we combine a computational model and rotating disk electrode measurements to investigate the effects from phosphate anion poisoning for the ORR on well-defined extended Pt surfaces. We construct a model including the poisoning effect from phosphate species on Pt(111) and Cu/Pt(111) based on density functional theory simulations. By varying the subsurface Cu content of the Cu/Pt(111) alloy, we tune the *OH binding energies on the surface by means of ligand effects, and as a result, we tune the ORR activity. We have investigated the effect of adsorbed phosphate species at low overpotentials when tuning *OH binding energies. Our results display a direct scaling relationship between adsorbed *OH and phosphate species. From the model, we observe how the three-fold binding sites of phosphate anions limit the packing of poisoning phosphate on the surface, thus allowing for *OH adsorption even when poisoned. Our work shows that, regardless of surface site blockage from phosphate, the trend in the catalytic oxygen reduction activity is predominantly governed by the *OH binding.</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
The importance of being together
No full textPlatinum catalyzes several chemical and electrochemical reactions that are central to humankind's use of energy, such as the electrochemical reduction of molecular oxygen, carbon monoxide oxidation, and the water-gas shift reaction to produce carbon dioxide and hydrogen from carbon monoxide and water. Two reports in the current issue provide insights into which platinum coordination number—defined as the number of nearest neighbors—may provide the highest catalytic activities for these reactions. On page 185, Calle-Vallejo et al. use the concept of generalized coordination numbers to show that concave atomic sites on a platinum single crystal are highly active for oxygen electroreduction (1). On page 189, Ding et al. use spectroscopic techniques to determine what role isolated Pt atoms play in CO oxidation and the water-gas shift reaction (2)
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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