1,721,002 research outputs found
Multicomponent nonprecious hydrogen evolution catalysts for high performance and durable proton exchange membrane water electrolyzer
No full textThe commercialization of proton exchange membrane water electrolysis (PEMWE) as an environmentally friendly energy storage technology requires the development of highly active non-Pt catalysts that are stable in acidic media. Nonprecious CuNiMo ternary catalysts with superior activity and durability for the hydrogen evolution are electrodeposited. A wide range of compositions, from Cu and Ni as single metals to binary and ternary alloys, are tested to identify the composition range in which the intrinsic activity is enhanced. In particular, Cu44.4Ni46Mo9.6 exhibits superior electrochemical characteristics, comparable to those of Pt group metals, with a Tafel slope of 27.7 mV dec(-1) and an overpotential of 18 mV at -10 mA cm(-2). Moreover, during a long-term durability test (24 h at -10 mA cm(-2)), the overpotential only decays by a few millivolts owing to the modified electronic structure obtained by alloying. PEMWE with Cu44.4Ni46Mo9.6 cathode exhibits 266% higher activity than the average activity of recently reported non-Pt cathode-based PEMWEs at 1.9 Vcell without degradation of performance during 48 h operation. Thus, Cu44.4Ni46Mo9.6 is a promising catalyst for the costefficient PEMWE.
Impact of Phosphide-Phosphate Ratio on NiCoP Catalysts for Hydrogen Evolution in Anion Exchange Membrane Water Electrolysis
No full textAlkaline and anion exchange membrane water electrolysis (AEMWE) presents a promising approach for hydrogen production. However, the slow kinetics of the alkaline hydrogen evolution reaction (HER) remains a significant challenge. This study aimed to enhance HER activity by optimizing transition metal-phosphorus compound catalysts, including Ni, Co, NiCo, NiP, CoP, and NiCoP. Their surface structure, crystallinity, electrochemical properties, and HER performance were meticulously studied. Among the catalysts, Ni28Co62P10 exhibited exceptional HER performance, achieving a low overpotential of 48 mV at a current density of -10 mA cm-2 in 1 M KOH. X-ray photoelectron spectroscopy analysis revealed that an optimal 1:1 balance of phosphate to phosphide is critical for achieving efficient HER. These findings emphasize the importance of balancing phosphorus species for optimal alkaline HER catalysis. Moreover, Ni28Co62P10 demonstrated excellent durability, maintaining high performance after 5000 cycles. In AEMWE single-cell tests, the catalyst achieved a cell voltage of 1.88 V at 1 A cm-2, surpassing the performance of Ni/Co-based catalysts from previous studies. The NiCoP-based catalysts in this study presented considerable promise for AEMWE systems, paving the way to the development of more efficient and durable catalysts for hydrogen production and advancing hydrogen-based renewable energy technologies.
Promoting oxygen evolution in proton exchange membrane water electrolysis: controlling the oxidation state of electrochemically fabricated iridium-cobalt oxide catalysts
No full textThe harsh corrosive environment and sluggish oxygen evolution reaction (OER) kinetics at the anode of proton exchange membrane water electrolysis (PEMWE) cells warrant the use of excess Ir, thereby hindering large-scale industrialization. To mitigate these issues, the present study aimed at fabricating a robust low-Ir-loading electrode via one-pot synthesis for efficient PEMWE. The pre-electrode was first prepared by alloying through the co-electrodeposition of Ir and Co, followed by the fabrication of Ir- Co oxide (Co-incorporated Ir oxide) electrodes via electrochemical dealloying. Two distinct dealloying techniques resulted in a modified valence state of Ir, and the effects of Co incorporation on the activity and stability of the OER catalysts were clarified using density functional theory (DFT) calculations, which offered theoretical insights into the reaction mechanism. While direct experimental validation of the oxygen evolution mechanism remains challenging under the current conditions, DFT-based theoretical modeling provided valuable perspectives on how Co incorporation could influence key steps in oxygen evolution catalysis. The Ir-Co oxide electrode with a selectively modulated valence state showed impressive performance with an overpotential of 258 mV at 10 mA cm-2, a low Tafel slope of 29.4 mV dec-1, and stability for 100 hat 100 mA cm-2 in the OER, in addition to a low overpotential of 16 mV at -10 mA cm-2 and high stability for 24 h in the hydrogen evolution reaction. The PEMWE cell equipped with the bifunctional Ir-Co oxide electrode as the anode and cathode exhibited outstanding performance (11.4 A cm-2 at 2.3 Vcell) despite having a low noble-metal content of 0.4 mgNM cm-2. (c) 2025 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
One-Pot Synthesis of Intermetallic Electrocatalysts in Ordered, Large-Pore Mesoporous Carbon/Silica toward Formic Acid Oxidation
No full textThis study describes the one-pot synthesis and single-cell characterization of ordered, large-pore (>30 nm) mesoporous carbon/silica (OMCS) composites with well-dispersed intermetallic PtPb nanoparticles on pore wall surfaces as anode catalysts for direct formic acid fuel cells (DFAFCs). Lab-synthesized amphiphilic diblock copolymers coassemble hydrophobic metal precursors as well as hydrophilic carbon and silica precursors. The final materials have a two-dimensional hexagonal-type structure. Uniform and large pores, in which intermetallic PtPb nanocrystals are significantly smaller than the pore size and highly dispersed, enable pore backfilling with ionomers and formation of the desired triple-phase boundary in single cells. The materials show more than 10 times higher mass activity and significantly lower onset potential for formic acid oxidation as compared with commercial Pt/C, as well as high stability due to better resistivity toward CO poisoning. In single cells, the maximum power density was higher than that of commercial Pt/C, and the stability highly improved, compared with commercial Pd/C. The results suggest that PtPb-based catalysts on large-pore OMCSs may be practically applied as real fuel cell catalysts for DFAFC.
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
Direct access to aggregation-free and small intermetallic nanoparticles in ordered, large-pore mesoporous carbon for an electrocatalyst
No full textAn intermetallic catalyst with ordered atomic arrays has a higher electrocatalytic activity than alloy, but the high temperature required for the formation makes the particles large, resulting in low mass activity. We report the simple synthesis of small Pt-based intermetallic nanoparticles on a carbon-based ordered mesoporous support by combining block copolymer-assisted evaporation-induced self-assembly and strong metal-support interaction (SMSI). Aluminosilicate in the mesostructured wall is an SMSI agent and charge transfer from Pt to the aluminosilicate suppresses the sintering of intermetallic nanoparticles. Intermetallic PtPb and Pt3Co on carbon-based mesoporous supports are synthesized, and their particle sizes are below 5 nm even at high loading. The PtPb catalyst shows 15 times higher mass activity for formic acid oxidation than Pt/C, and the Pt3Co catalyst shows 3.25 times higher mass activity for oxygen reduction than Pt/C. This procedure can be extended to synthesize various heterogenous catalysts that require high temperature for synthesis or to operate.
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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