37 research outputs found
Vers un nouveau concept de batterie protonique
No full textLes batteries Ni-MH sont des systèmes de stockage d'énergie largement utilisés qui sont reconnues pour leur bonne cyclabilité, une densité énergétique compétitive, un faible effet mémoire, une large gamme de températures de fonctionnement, un faible coût et leur respect de l'environnement. Malgré ces avantages notables, leur utilisation est limitée par une énergie spécifique relativement modeste et du problème de vieillissement des matériaux d’électrodes. Ces limitations sont principalement dues à l'utilisation d'un électrolyte alcalin (KOH) qui est assez agressif avec une fenêtre de potentiel électrochimique (EPW) relativement limitée. Ce travail vise à proposer un électrolyte alternatif pour l'électrode négative de stockage d'hydrogène des batteries Ni-MH afin de remplacer l'électrolyte aqueux KOH 8,7 M conventionnel et surmonter les inconvénients susmentionnés. Plusieurs liquides ioniques et leurs mélanges ont été synthétisés et leurs propriétés physicochimiques ont été étudiées. Trois liquides ioniques, l'acétate de pyrrolidinium, l'acétate d'éthanolammonium et l'acétate de diéthanolammonium, ont été utilisés avec succès comme électrolyte avec l'électrode négative de la batterie et une capacité de décharge maximale de 295 mAh.g-1 a été obtenue lors de l'utilisation du mélange acide acétique 2M / acétate de pyrrolidinium. Tous ces électrolytes ont une EPW élargie par rapport à l'électrolyte KOH (0.20 à 0.41 V). Cet élargissement permet d’entrevoir des possibilités pour de nouveaux types d'électrodes dont l'utilisation était limitée en raison de l'étroitesse de l'EPW de l'eau, ce qui permet d'augmenter de manière significative la puissance spécifique de la batterie Ni-MH. La corrosion calendaire de l'alliage de l'électrode négative a été étudiée ainsi que la dégradation de l'électrode négative pendant le fonctionnement de la batterie. Il a été montré que l'utilisation de [Pyrr][Ac] et [DEAO][Ac] limite significativement la corrosion de l'alliage typiquement observée dans l'électrolyte KOH, qui est la cause principale de la dégradation de la batterie Ni-MH commerciale, pendant le fonctionnement de la batterie et la corrosion calendaire.Ni-MH battery is widely used energy storage systems, which are recognized for their good cyclability, competitive energy density, low memory effect, wide range of operating temperatures, low cost, and environmental friendliness. Despite these notable advantages, their widespread adoption is still limited by the relatively modest specific energy and the challenge of electrode aging. Those limitations are mainly affected by the use of quite aggressive water-based KOH electrolyte and with a relatively low Electrochemical Potential Window (EPW). This work aims to propose an alternative electrolyte for hydrogen storage negative electrode of Ni-MH batteries to replace the conventional water-based KOH 8.7 M and overcome aforementioned drawbacks. Series of PILs and their mixtures have been synthetized, and their physicochemical properties have been studied. Three ionic liquids, Pyrrolidinium Acetate, Ethanolammonium Acetate and Diethanolammonium acetate, showed successful use as electrolyte with negative battery electrode, with a maximum discharge capacity of 295 mAh.g-1 when working in a mixture 2M Acetic Acid / Pyrrolidinium Acetate. All these electrolytes have enlarged EPW compare to KOH electrolyte, with an increase of 0.20 to 0.41 V. This enlargement paves the way for possibilities of using new type of electrodes which were limited due to the narrow EPW of water. It can thus significantly increase the specific power of Ni-MH battery. The calendar corrosion of the negative electrode alloy was studied as well as degradation of the negative electrode while battery was operating. It was shown that use of [Pyrr][Ac] and [DEAO][Ac] prevents the corrosion of the alloy typically observed in KOH electrolyte, which is the main cause of the degradation of the commercial Ni-MH battery, during battery performance and calendar corrosion
Surfactant Self-Assembly Nanostructures in Protic Ionic Liquids
No full textThe existence and properties of mesoscopic self-assembly structures formed by surfactants in protic ionic liquid solutions are reported. Micellar aggregates of n-alkyltrimethylammonium (n = 10, 12, 14, 16) chlorides and bromides and of n-alkylpyridinium (n = 12, 16) chlorides in ethylammonium nitrate and propylammonium nitrate were observed by means of several experimental techniques, including surface tension, transmission electron micrography, dynamic light scattering, and potentiometry using surfactant-selective electrodes. The effect of the alkyl chain length of both solute and solvent molecules on the critical micelle concentration is discussed, and a Stauff-Klevens law is seen to apply to surfactant solutions in both protic ionic liquids. The counterion role is also a matter of study in the case of alkyltrimethylammonium-based surfactants, and the presently reported evidence suggests that the place of the surfactant counterion in the Hoffmeister's series could determine its effect on micellization in IL solution. The size distribution of the aggregates is also analyzed together with the Gibbs free energies of micellization and the minimum surface area per monomer in all of the studied cases. All of the hereby reported evidence suggests that the negative entropic contribution arising from the release of the solvent layer upon micellization is also the driving force of conventional surfactant self-association in protic ionic liquids. © 2011 American Chemical Society
Membrane electrodes sensitive to doubly charged surfactants. Application to a cationic gemini surfactant.
No full textInternational audienceThe response of a membrane electrode is not always identical to that of a redox electrode. Indeed, in the case of membrane electrode the response is not due to a redox equil. but to a cross-membrane potential. So, the membrane electrode's response depends mainly on the carrier system and the nature of the membrane. The properties of the membrane can favor several reactions giving rise to different ionic species diffusing in the membrane. The expression of the cross-membrane potential thus depends on the no. and quantities of these ionic species. To illustrate this, we established the equations for the case of a two-charge cation detected by a univalent charged carrier. We show that the Nernstian response is not applicable to membrane electrodes. This approach allowed us to interpret results obtained with a cationic gemini surfactant-selective electrode prepd. in the lab. To prove the well working of this electrode, we detd. the crit. micelle concn. in water and several NaBr solns. (0.004, 0.006, 0.01 and 0.02 M) from which the counterion binding has been detd
Étude électrochimique du nitrate d'éthylammonium fondu à 298 K : établissement d'une échelle de potentiel redox
No full textLe nitrate d'éthylammonium (NEA) est un sel fondu à température ordinaire, miscible à l'eau et à certains solvants organiques comme le méthanol. Ses propriétés solubilisantes vis à vis des
composés organiques ou minéraux et sa conductivité intrinsèque en font un milieu intéressant pour des études électrochimiques. Le but de cet article est de présenter quelques propriétés
physiques et électrochimiques de ce solvant. Le potentiel de charge nulle (Epcn) de l'électrode à goutte de mercure a été déterminé par mesure de la tension interfaciale. L'analyse de la courbe
électrocapillaire montre que la charge négative de l'électrode à est plus faible dans le NEA que dans l'électrolyte aqueux NaNO3 (1 M). Cet effet a été attribué à la taille de l'ion
éthylammonium adsorbé à l'interface. Le domaine d'électroactivité du NEA a été déterminé sur électrode de platine, carbone et mercure. Quelques systèmes redox courants, minéraux et
organiques, ont été étudiés par les méthodes électrochimiques usuelles : potentiométrie, polarographie, voltammétrie à l'électrode tournante et voltammétrie cyclique. L'étude électrochimique
de ces systèmes dans le NEA montre la dualité de ce solvant qui se comporte tantôt comme un solvant protique (comme l'eau ou les alcools), tantôt comme un solvant dipolaire aprotique
(comme le DMF ou l'acétonitrile). La détermination des potentiels standard des couples étudiés a permis d'établir une échelle d'oxydo-réduction qui a été comparée à l'échelle aqueuse
Pseudolattice theory of charge transport in ionic solutions: Corresponding states law for the electric conductivity
No full textInternational audienceA statistical mechanical framework for charge transport in ionic liquid–solvent mixtures based on the existence of a statistical lattice structure (pseudolattice) throughout the whole range of concentration is reported. The ion distribution is treated in a mean-field Bragg–Williams-like fashion, and the ionic motion is assumed to take place through hops between cells of two different types separated by non-random-energy barriers of different heights depending on the cell type. Assuming non-correlated ion transport, the electrical conductivity is shown to have a maximum, arising from the competition between the concentration of charge carriers in the bulk medium and their mobilities in the pseudolattice. An explicit expression for the concentration at which this maximum occurs is given in terms of microscopic parameters, and the electrical conductivity normalized by its maximum value (κ/κmax) is shown to follow rather closely a universal corresponding states law in concentration space when represented against the ionic concentration scaled by its value at the conductivity maximum (ϕα/ϕmax). Ion–ion and ion–solvent interactions are explicitly considered combining the path probability method for charge transport in solid electrolytes and the Bragg–Williams approximation for interparticle interactions, and their impact on the deviations of experimental data from the universal behavior of non-correlated transport analyzed. The theoretical predictions are shown to satisfactorily predict experimental values of electrical conductivity of aqueous solutions of conventional electrolytes and of mixtures of room temperature molten salts with typical solvents
In-line and in situ monitoring of ionic surfactant dynamics in latex reactors using conductivity measurements and ion-selective electrodes
No full textIn-line and in situ monitoring of ionic surfactant dynamics in latex reactors using conductivity measurements and ion-selective electrodes
No full textInternational audienc
Effect of ZnO surface morphology on its electrochemical performance
No full textThe purpose of this paper is to bridge the gap between ZnO surface morphology and its electrochemical
performance. For this reason, ZnO nanowires (NWs) of different length were synthesized using an
electrochemical method. Then, the electrochemical performance of the synthesized ZnO surfaces was
studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical
analysis results revealed that the increase of ZnO NW length contributes to the retrogression of
electrochemical performance. Indeed, the electrochemical performance is mainly related to the
wettability behavior of the ZnO nanowire surfaces. When the ZnO NWs length increases, the surface
become more hydrophobic, therefore, charge transfers between the electrode/electrolyte decrease. To
improve the electrochemical performance of ZnO, we propose a new strategy combining NWs and
microsheets (mSs) for further improving the morphology. Finally, the surfaces based on the double
structure of ZnO provide good propagation of charge at the surface, good transfer in the electrode,
good stability, and excellent scanning ability. In the present work we intend to pave the way for
achieving high electrochemical performance ZnO-based layersThis work was supported by the Erasmus+ programme of the
European Union (Grant No. 2016-1-FR01-KA107-023012), the
Scientic and Technological Cooperation Program between
Portugal (FCT) and Morocco (CNRST) – 2019/2020, and Portu guese Foundation for Science and Technology in the framework
of the Strategic Funding UIDB/FIS/04650/2020 (JPBS). The
experimental part of this work was performed on Laboratoire
Interfaces et Syst`emes Electrochimiques (LISE), Sorbonne Universit´e, 75005 Paris, France. The authors express their thank to M. TURMINE and V. Vivier for their rigorous discussions, and
F. Pillier and S. Delbrel for FEG-SE
In-line and in situ monitoring of ionic surfactant dynamics in latex reactors using conductivity measurements and ion-selective electrodes
No full textInternational audienc
