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Monnier J.,CNRS East Paris Institute of Chemistry and Materials Science | Chen H.,CNRS East Paris Institute of Chemistry and Materials Science | Joiret S.,Paris-Sorbonne University | Joiret S.,CNRS Laboratory Interfaces & Systems Electrochemistry | And 2 more authors.
Journal of Power Sources | Year: 2014

To improve the performances of Nickel-Metal Hydride batteries, an important step is the understanding of the corrosion processes that take place in the electrode material. In particular, the present study focuses for the first time on the model (La, Mg)2Ni7 system. The calendar corrosion in 8.7 M KOH medium was investigated from 6 h to 16 weeks immersion. By a unique combination of structural and elemental characterisations, the corrosion products are evidenced in those systems. In particular, we demonstrate that Ni and Mg combine in a pseudo-binary hydroxide Mg1-xNi x(OH)2 whereas La corrodes into nanoporous La(OH) 3 needles with inner hollow nanochannels. © 2014 Elsevier B.V. All rights reserved.

Alexander C.L.,University of Florida | Tribollet B.,CNRS Laboratory Interfaces & Systems Electrochemistry | Orazem M.E.,University of Florida
Electrochimica Acta | Year: 2016

Finite-element simulations were performed to determine the influence of a radial distribution of capacitance on the impedance of ideally polarized disk electrodes. The characteristic length associated with this form of distribution was found to be the period of the distribution. This work showed that while a capacitance distribution causes frequency dispersion, this effect is seen only at frequencies that are much higher than those associated with the disk-geometry-induced frequency dispersion. Thus, a constant-phase-element associated with a surface distribution of time constants cannot be attributed to a distribution of capacitance. © 2015 Elsevier Ltd. All rights reserved.

Lugaresi O.,University of Milan | Perales-Rondon J.V.,University of Alicante | Minguzzi A.,University of Milan | Solla-Gullon J.,University of Alicante | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2015

Electrochemical abatement of volatile polychlorinated organic compounds for environmental applications represents a very attractive and feasible alternative for working at mild reaction conditions and reduced costs. We present herein the synthesis of three different sized Ag nanoparticles (NPs) and their electrocatalytic performance in the degradation of a model pollutant (trichloromethane, CHCl3) in aqueous media. Two different methodologies are used: A conventional study based on voltammetry and chronoamperometry and a novel screening approach based on the micropipette delivery/substrate collection (MD/SC) mode of the scanning electrochemical microscopy (SECM). This new approach allows to dose any reactant, in this case CHCl3, even if the latter cannot be electrogenerated. Moreover, we introduce here a novel platform for studying nanomaterials by reducing the current collector background contribution using disposable screen-printed array electrodes. The performance ranking obtained by the SECM for the three different samples of Ag NPs synthesized is validated by its comparison with the results obtained by chronoamperometry, which demonstrates the feasibility and the good sensitivity of SECM in electrocatalysts screening for the CHCl3 reduction reaction. In addition, SECM allows to analyze simultaneously a large number of catalysts in one single experiment under constant experimental conditions. We suggest the proper size range and the presence of abundant superficial defective sites, such as steps or kinks, as the main reasons for Ag NPs C1 exhibiting the best overall catalytic performance in trichloromethane electrochemical reduction. © 2014 Elsevier B.V.

Faure M.,CNRS Laboratory Interfaces & Systems Electrochemistry | Sotta B.,CNRS Developmental Biology Laboratory | Gamby J.,CNRS Laboratory Interfaces & Systems Electrochemistry
Biosensors and Bioelectronics | Year: 2014

Real time monitoring of electrolyte resistance changes during hydrolysis of 4-nitrophenylphosphate (pNPP) by alkaline phosphatase (ALP) bound on paramagnetic-beads was performed into a small dielectric channel. The reaction kinetic fit with a non-competitive substrate-inhibition equation. Michaelis-Menten apparent constant, KMapp, was determined as 0.33±0.06mM and the maximum apparent rate, Vmaxapp as 98±5pMs-1. The detection limits were 15fM for ALP and 0.75mM for pNPP. © 2014 Elsevier B.V.

Joiret S.,CNRS Laboratory Interfaces & Systems Electrochemistry | Pillier F.,CNRS Laboratory Interfaces & Systems Electrochemistry | Lemarchand A.,CNRS Laboratory of Theoretical Physics and Condensed Matter
Journal of Physical Chemistry C | Year: 2014

To propose a picture of plaster hydration at a submicrometric scale, we have developed a kinetic Monte Carlo simulation model of gypsum crystal growth. Raman spectroscopy is used to check the model and to assign physical values to the parameters. Special focus is put on the effects of increasing plaster-to-water ratio and using citric acid as an additive. The hypothesis about the autocatalytic growth of gypsum needles during the first stage of the reaction is confirmed by the correct simulation of the induction period preceding the fast growth regime. The aspect ratio of gypsum needles, defined as the ratio of needle length and width, emerges as a relevant parameter to control both dynamics and material structure. Addition of citric acid is known to produce compact gypsum crystals instead of long needles. The choice of a small aspect ratio is sufficient for the simulations to reproduce the effects of citric acid, including the slowing down of the reaction without recourse to fitting parameters. The kinetic Monte Carlo simulation model proved to be a predictive tool that could assist the rational development of novel additives and reagent treatments with the aim of producing materials with predefined properties. © 2014 American Chemical Society.

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