1,721,060 research outputs found
Coupled System of Modified Membrane and Modified Cathode for Efficient PEM-FC
No full textA coupled system formed by polyoxometalate (POM)-modified ultra-low Pt loading cathode and sulphated titania (S-TiO2)-doped Nafion membrane is evaluated in a proton exchange membrane (PEM) fuel cell (FC). Modification of fuel cell cathode is performed using Kegging-type polyoxometalate and low Pt loading, in order to enhance active area and mesoporosity [1]. Commercial Nafion is modified with superacidic sulphated titanium oxide nanoparticles, in order to improve the proton transfer and the hydration level in the membrane-electrode assembly (MEA) [2,3]. The cell performance is studied at different relative humidity with polarization dependence and electrochemical impedance spectroscopy at high and low current density. Analysis of cell performance shows that the catalytic and transport properties are improved, with respect to unmodified commercial materials, using the coupled system, despite the ultra- low Pt loading used, thanks to rich proton environment provided from both cathode and membrane
Conductivity and Dielectric Relaxations in New Morpholinium- and Piperidinium-Based Ionic Liquids
No full textRoom Temperature Ionic Liquids (RTILs) are key materials for the development of new energy storage and conversion systems [1]. In the past decade several relevant properties such as their negligible vapour pressure, non-flammability, and high roomtemperature conductivity were explored in order to obtain safer and better performing devices [2]. Despite of this, the complex interplay existing between the IL nanostructure and the conductivity mechanism is still under discussion within the scientific community [3]. Following this, the synthesis of new ILs and the investigation of their electrical properties are of crucial importance and could pave the way to new applications in the field of ion-conducting materials [4, 5].
This contribution summarizes the electrical study of a family of ILs based on 1-methylmorpholinium (MM+) and 1-methylpiperidinium (MP+) cations. The MM+ and MP+ cations have been synthesized comprising two different alkyl side chain substituents on the nitrogen atom, namely 1-methoxyethyl (ME) and 1-ethoxyethyl (EE) groups. A set of four cations (ME-MM+, EE-MM+, ME-MP+ and EEMP+) neutralized by TFSI-anions is obtained, thus giving rise to four new RTILs.
The structure of these ILs allows the systematic investigation of the presence of oxygen atoms on the aliphatic ring (see morpholinium vs. piperidinium cations) with respect to the different substituent side chain length (see methoxyethyl vs.ethoxyethyl groups). The effect of the oxygen atom position on the diffusion of conformational states as well as the charge transfer mechanism is particularly interesting for future Lithium battery applications in which the oxygen atoms are expected to play a crucial role on the migration of Li cations.
At this regard, Broadband Electrical Spectroscopy (BES) measurements were undertaken to elucidate the electrical response of the ILs in terms of dielectric relaxations and polarization phenomena. At TTg, interdomain polarization events are detected. These polarization events are associated with the presence of cation and anion nanocluster aggregates with different permittivities.
The results allow us to correlate the dielectric relaxations of the different cations with the overall long-range charge migration, thus elucidating the interplay existing between conductivity and nanostructure of this new ILs.
References
[1] H. Ohno, ed., Electrochemical Aspects of Ionic Liquids, 2nd ed., John Wiley & Sons, Hoboken, NJ, USA, 2005.
[2] F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, et al., A Key concept in Magnesium Secondary Battery Electrolytes., ChemSusChem. 8 (2015) 3069–76.
[3] A. Tsurumaki, F. Bertasi, K. Vezzù, E. Negro, V. Di Noto, H. Ohno, Dielectric relaxations of polyether-based polyurethanes containing ionic liquids as antistatic agents., PCCP. 18 (2016) 2369–78.
[4] F. Bertasi, F. Sepehr, G. Pagot, S.J. Paddison, V. Di Noto, Toward a Magnesium-Iodine Battery, Adv. Funct. Mater. 26 (2016) 4860–4865.
[5] M. A. Navarra, K. Fujimura, M. Sgambetterra, S. Panero, A. Tsurumaki, N. Nakamura, H. Ohno, B. Scrosati, New morpholinium- and piperidinium-based ionic liquids, functionalized with ethoxyethyl-side chains, as electrolyte components in lithium and lithium-ion batteries, ChemSusChem. 2017, in press, doi: 10.1002/cssc.201700346
Front Cover: Enhancing oxygen reduction reaction catalytic activity using a sub‐stoichiometric CaTiO3−δ additive (ChemElectroChem 24/2019)
No full textThe Front Cover shows a rotating disk electrode pinball where, thanks to the presence of the sub‐stoichiometric calcium titanate perovskite, the oxygen reduction reaction is facilitated to proceed via the four‐electron pathway. More information can be found in the Communication by L. Mazzapioda et al. on page 5941 in Issue 24, 2019 (DOI: 10.1002/celc.201901292)
Hybrid membranes based on sulfated titania nanoparticles as low-cost proton conductors
No full textThis work reports on a novel, hybrid solid-state membrane based on sulfated titania nanoparticles stabilized by a polyvinylidene fluoride-hexafluoropropylene copolymer. A fast solvent-casting technique was adopted as a valid alternative to a fully dry, hot-pressing preparation procedure. Self-standing, flexible membranes with high proton conductivity were obtained
Titanium-Based Tetrakis-2,3-[5,6-di(Substituted)pyrazino]porphyrazine: Synthesis and Characterization
Get PDFTetrapyrazinoporphyrazine (TPysPz) ligands and metal complexes find, generally, application as electronic materials and catalysts. Considering the limited application of Titanium (Ti), we prepared and characterized a family of ligands and Ti-based complexes of tetrakis-2,3-[5,6-di-R8-pyrazino]porphyrazine (R = H, 2-Py, Ph). UV/Vis measurements in different solvents confirm molecular aggregation, which results more pronounced in the presence of 2-pyridil and phenyl substituents on the macrocycle edge. Because of low solubility, solid state NMR was applied for structure characterization. Additional IR and MALDI-TOF were carried out to complete the characterization. Cyclic voltammetry in DMSO/Bu4NBF4 0.1 m unveiled that our Ti complexes can take part in up to five redox events. The first two quasi-reversible reductions involve Ti(IV), whereas the further to or three occur at the expense of the TPysPz macrocycle. To test the applicability of our compounds as catalytic materials, we performed a preliminary cyclic voltammetry investigation in the solid-state, which showed typical peaks of hydrogen redox reactions
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
An advanced lithium-ion battery based on a nanostructured Sn-C anode and an electrochemically stable LiTFSi-Py24TFSI ionic liquid electrolyte
No full textWe report here a detailed impedance analysis of the interface between a selected IL electrolyte, i.e. a solution of lithium N, N-bis(trifluoromethane sulfon) imide in N-n-butyl-N-ethyl pyrrolidinium and a N, N-bis(trifluoromethane sulfon) imide, LiTFSI-Py24TFSI, and two electrodes, namely a conventional lithium metal and an advanced nanostructured Sn-C alloy, respectively. We show that the Sn-C alloy, in virtue of a specific formation of a surface protecting film, has an interface much more stable than that of the Li electrode. This favourable property is exploited for using Sn-C as a new anode for the development of an advanced lithium-ion battery based on LiTFSI-Py24TFSI as the electrolyte and on olivine LiFePO4 as the cathode. The results demonstrated that this battery has very promising performances in terms of cycle life and rate capability. (C) 2009 Elsevier B. V. All rights reserved
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