CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems

Paris, France

CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems

Paris, France
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Haigis V.,German Research Center for Geosciences | Salanne M.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Jahn S.,German Research Center for Geosciences
Earth and Planetary Science Letters | Year: 2012

We report lattice thermal conductivities of MgO and MgSiO3 in the perovskite and post-perovskite structures at conditions of the Earth's lower mantle, obtained from equilibrium molecular dynamics simulations. Using an advanced ionic interaction potential, the full conductivity tensor was calculated by means of the Green-Kubo method, and the conductivity of MgSiO3 post-perovskite was found to be significantly anisotropic. The thermal conductivities of all three phases were parameterized as a function of density and temperature. Assuming a Fe-free lower-mantle composition with mole fractions xMgSiO3=0.66 and xMgO=0.34, the conductivity of the two-phase aggregate was calculated along a model geotherm. It was found to vary considerably with depth, rising from 9.5W/(mK) at the top of the lower mantle to 20.5W/(mK) at the top of the thermal boundary layer above the core-mantle boundary. Extrapolation of experimental data suggests that at deep-mantle conditions, the presence of a realistic amount of iron impurities lowers the thermal conductivity of the aggregate by about 50% (Manthilake et al., 2011a). From this result and our thermal conductivity model, we estimate the heat flux across the core-mantle boundary to be 10.8TW for a Fe-bearing MgO/MgSiO3 perovskite aggregate and 10.6TW for a Fe-bearing MgO/MgSiO3 post-perovskite aggregate. © 2012 Elsevier B.V.


Pagonabarraga I.,University of Barcelona | Rotenberg B.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Frenkel D.,University of Cambridge
Physical Chemistry Chemical Physics | Year: 2010

Electrokinetic phenomena are of great practical importance in fields as diverse as micro-fluidics, colloid science and oil exploration. However, the quantitative prediction of electrokinetic effects was until recently limited to relatively simple geometries that allowed the use of analytical theories. In the past decade, there has been a rapid development in the use of numerical methods that can be used to model electrokinetic phenomena in complex geometries or, more generally, under conditions where the existing analytical approaches fail. The present paper discusses these recent developments, with special emphasis on the advent of coarse-grained models that make it possible to bridge the gap between a purely atomistic and macroscopic descriptions. © 2010 the Owner Societies.


Rotenberg B.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Pagonabarraga I.,University of Barcelona
Molecular Physics | Year: 2013

Electrokinetic effects, i.e. the coupled hydrodynamic and electric phenomena which occur near charged interfaces, constitute a challenge to theorists due to the variety of length and time scales involved. We discuss recent advances in the modelling of these phenomena, emphasising the interplay between the molecular specificity and the collective induced flows that emerge. We discuss the complementary simulation methodologies that have been developed either to focus on the molecular aspects of electrokinetics or on their effective properties on larger scales, as well as the proposed hybrid schemes that can incorporate both aspects. We highlight the insights that molecular studies have brought on the nature of interfacial charges and their implications for kinetic phenomena in confined fluids and also discuss advances in a number of relevant contexts. © 2013 Taylor & Francis.


Sulpizi M.,Johannes Gutenberg University Mainz | Salanne M.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Sprik M.,University of Cambridge | Gaigeot M.-P.,University of Évry Val d'Essonne | Gaigeot M.-P.,Institut Universitaire de France
Journal of Physical Chemistry Letters | Year: 2013

The vibrational sum frequency generation (VSFG) spectrum of the water liquid-vapor (LV) interface is calculated using density functional theory-based molecular dynamics simulations. The real and imaginary parts of the spectrum are in good agreement with the experimental data, and we provide an assignment of the SFG bands according to the dipole orientation of the interfacial water molecules. We use an instantaneous definition of the surface, which is more adapted to the study of interfacial phenomena than the Gibbs dividing surface. By calculating the vibrational (infrared, Raman) properties for interfaces of varying thickness, we show that the bulk spectra signatures appear after a thin layer of 2-3 Å only. We therefore use this value as a criterion for calculating the VSFG spectrum. © 2012 American Chemical Society.


Merlet C.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Salanne M.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Rotenberg B.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Madden P.A.,University of Oxford
Journal of Physical Chemistry C | Year: 2011

A recently developed coarse-grained model (J. Phys. Chem. B, 2010, 114, 12629-12631), previously validated against experimental data for a number of bulk properties, is used in molecular dynamics simulations of two different interfaces involving the ionic liquid [BMI][PF6]. First, simulations of the liquid-vapor interface demonstrate that the model is able to predict the surface tension of the fluid (for which we obtain a value of 39.4 mN•m -1 at 400 K). Second, simulations were performed at constant potential differences applied between two graphite electrodes. From simulations with different applied potentials, the differential capacitances of the positive and negative electrodes can be calculated. It appears that both capacitances (C+ = 3.9 μF•cm-2 for the positive electrode and C- = 4.8 μF•cm-2 for the negative electrode) agree very well with simulations results obtained with an all-atom model. The coarse-grained model also accurately reproduces the two-dimensional structure observed at the graphite-ionic liquid interface, namely, a defective hexagonal lattice with a lattice spacing of approximately 10 Å. © 2011 American Chemical Society.


Mauger A.,CNRS Institute of Mineralogy, Materials Physics and Cosmochemistry | Julien C.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems
Ionics | Year: 2014

The research on the electrodes of Li-ion batteries aims to increase the energy density and the power density, improve the calendar and the cycling life, without sacrificing the safety issues. A constant progress through the years has been obtained owing to the surface treatment of the particles, in particular the coating of the particles with a layer that protects the core region from side reactions with the electrolyte, prevents the loss of oxygen, and the dissolution of the metal ions in the electrolyte, or simply improve the conductivity of the powder. The purpose of the present work is to review the different surface modifications that have been tried in the past for the different electrodes that are currently commercialized, or considered as promising, including the three families of positive electrodes (lamellar, spinel, and olivine families) and the three negative electrodes (carbon, Li4Ti5O12, and silicon). The role of the different coats used to improve either the surface conductivity, or the thermal stability, or the structural integrity is discussed. The limits in the efficiency of these different coats are also analyzed along with the understanding of the surface modifications that have been proposed. © 2014 Springer-Verlag Berlin Heidelberg.


Abou-Hassan A.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Sandre O.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Cabuil V.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems
Angewandte Chemie - International Edition | Year: 2010

Even flow: Microreactors are a new and convenient tool for liquid-liquid extraction and the optimization of inorganic chemical reactions. Fundamental studies have been carried out by this technique to understand the phenomena of nucleation and growth during chemical processes. Up-to-date data is provided, and the role of microfluidics in the field of inorganic chemistry is discussed. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Dahirel V.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Jardat M.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems
Current Opinion in Colloid and Interface Science | Year: 2010

The keystone of the modelling of complex systems is the potential of mean force (PMF) between particles. This review focuses on recent numerical simulation studies that concern the computation of the PMF between charged nanoparticles in solution. Such simulations explicitly sample the configurations of the microions or water molecules over which the potential is averaged out. The studies rely on different levels of modelling and permit to quantify the relative amplitude of the different factors governing the interaction, such as the structure of the nanoparticle, the polarisability of microions, or hydrophobic interactions. We discuss the conditions in which the potential of mean force can safely be expressed as a DLVO potential, and why in some cases such a simple analytical expression cannot be used. © 2009 Elsevier Ltd. All rights reserved.


Devilliers D.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Mahe E.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems
Electrochimica Acta | Year: 2010

Titanium is a valve metal able to withstand corrosion, due to the presence of a passivating layer of titanium oxide on its surface. But, due to that more or less insulating layer, titanium cannot be used directly as an anodic material. However, modification of the surface of a Ti/TiO2 substrate may lead to the formation of new structures: Ti/TiO2/M or Ti/TiO2/OX, in which M is a metal such as platinum and OX a conducting oxide exhibiting electrocatalytic properties. These structures have interesting electrochemical properties and may be used as efficient electrode materials. In this paper, after a review of the electrochemical behaviour of these structures, we give new results concerning the selective electrodeposition of lead dioxide on Ti/TiO2 substrates and we propose an interpretation of the results taking into account the dielectric properties of the underlying TiO2. It is shown that there is a dramatic decrease of the resistance of the electrode when a PbO2 layer is electrodeposited onto a Ti/TiO2 structure. That effect allows the preparation of electrodes (low-cost DSAs) that may be used as anodes in spite of the presence of the underlying TiO2 layer, that layer being useful to avoid corrosion of the titanium substrate. At last, the effect of stabilization of the underlying TiO2 layer is discussed. © 2010 Elsevier Ltd. All rights reserved.


Merlet C.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Salanne M.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Rotenberg B.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems
Journal of Physical Chemistry C | Year: 2012

We introduce new coarse-grained models for two imidazolium-based ionic liquids, namely, 1-butyl-3-methyl-imidazolium tetrafluoroborate [BMI][BF 4] and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMI][BF 4], derived from the original force field of Roy and Maroncelli (J. Phys. Chem. B2010, 114, 12629-12631) representing the 1-butyl-3- methylimidazolium hexafluorophosphate [BMI][PF 6] ionic liquid. We evaluate static and dynamic properties between 298 and 500 K and show that they agree with previous experimental and all-atom simulation studies. The models are used to conduct simulations of the liquid-vapor interface and accurately predict surface tensions at 400 K. Capacitive properties are also examined by doing molecular dynamics simulations of the ionic liquids in contact with graphite electrodes. The obtained structures and capacitances are consistent with all-atom simulation results reported on these systems. © 2012 American Chemical Society.

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