Preparation of new proton exchange membranes using sulfonated poly(ether sulfone) modified by octylamine (SPESOS)

Sulfonated poly(arylene ether sulfone) (SPES) has received considerable attention in membrane preparation for proton exchange membrane fuel cell (PEMFC). But such membranes are brittle and difficult to handle in operation. We investigated new membranes using SPES grafted with various degrees of octylamine. Five new materials made from sulfonated polyethersulfone sulfonamide (SPESOS) were synthetized with different grades of grafting. They were made from SPES, with initially an ionic exchange capacity (IEC) of 2.4 meq g−1 (1.3 H+ per monomer unit). Pristine SPES with that IEC is water swelling and becomes soluble at 80 °C, its proton conductivity is in the range of 0.1 S cm−1 at room temperature in aqueous H2SO4 1 M, similar to that of Nafion®. After grafting with various amounts of octylamine, the material is water insoluble; membranes are less brittle and show sufficient ionic conductivity. Proton transport numbers were measured close to 1

Reversible magnesium and aluminium ions insertion in cation-deficient anatase TiO₂

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Intracellular degradation of functionalized carbon nanotube/iron oxide hybrids is modulated by iron via Nrf2 pathway.

The in vivo fate and biodegradability of carbon nanotubes is still a matter of debate despite tremendous applications. In this paper we describe a molecular pathway by which macrophages degrade functionalized multi-walled carbon nanotubes (CNTs) designed for biomedical applications and containing, or not, iron oxide nanoparticles in their inner cavity. Electron microscopy and Raman spectroscopy show that intracellularly-induced structural damages appear more rapidly for iron-free CNTs in comparison to iron-loaded ones, suggesting a role of iron in the degradation mechanism. By comparing the molecular responses of macrophages derived from THP1 monocytes to both types of CNTs, we highlight a molecular mechanism regulated by Nrf2/Bach1 signaling pathways to induce CNT degradation via NOXjournal article2017 Jan 252017 01 25importe

Nonclassical Nucleation and Growth of Pd Nanocrystals from Aqueous Solution Studied by In Situ Liquid Transmission Electron Microscopy

Direct visualization and understanding of the atomic mechanisms governing the growth of nanomaterials are crucial for designing synthesis strategies of high specificity. Aside from playing a key role in numerous technological applications, palladium clusters and nanoparticles are particularly valuable due to their outstanding catalytic activity. Studies show that the properties of Pd nanomaterials depend on shape and size. Therefore, optimizing the synthesis to control the final size and shape of Pd nanoparticles is important for a large number of current and future applications. In this work, we exploit in situ liquid cell scanning transmission electron microscopy to track at the atomic scale the growth of Pd nanoparticles from the very early stage to mature, crystalline nanoparticles. We find that the formation of Pd nanoparticles consists of multiple steps. The first step in nanoparticle formation, representing a nonclassical nucleation step, can be described by the formation of agglomerates of Pd atoms. In the second step, these agglomerates grow via atomic addition to form primary nanoclusters, which coalesce to form amorphous clusters. In the third stage, these clusters continue to coalesce, leading to the formation of amorphous Pd NPs, while in parallel, growth by monomer attachment continues. Then, in the fourth step, the amorphous nanoparticles undergo a nanocrystallization process, where the continuous improvement of crystallinity and the establishment of a distinct morphology eventually give rise to the formation of facetted, crystalline nanoparticles. Similar to our earlier work with Au and Pt nanoparticles, these results confirm that even for simple systems, nonclassical nucleation and growth processes dominate and that these multi-step mechanisms are highly element-specific. Despite the fact that the synthesis conditions are identical, the element-specific interactions define the pathway of the formation of crystalline nanoparticles

In-Situ Liquid/Bias Transmission Electron Microscopy to Visualize the Electrochemical Lithiation/Delithiation Behaviors of LiFe 0.5 Mn 0.5 PO 4

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In-Situ

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In Situ Electron Diffraction using Liquid-Electrochemical TEM for Monitoring Structural Transformation in Single Crystals Of Cathode Materials for Li-Ion Batteries

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Preparation and characterization of mechanically alloyed AB(3)-type based material LaMg2Ni5Al4 and its solid-gaz hydrogen storage reaction

International audienceWe developed in the present paper the synthesis of a new AB(3)-type compound LaMg2Ni5Al4 by mechanical alloying (MA) process. X-ray diffraction analysis (XRD) was used to determine the structural properties and the phase evolution of the powder mixtures. Two different synthesis pathways have been investigated. The first starting from elemental metals and the second from a mixture of two binary compounds LaNi5 (CaCu5-type structure, P6/mmm space group) and Al(Mg) solid solution (cubic Fm-3 m space group). The results show multiphase alloys which contain LaMg2Ni5Al4 main phase with hexagonal PuNi3-type structure (R-3 m space group). Rietveld analysis shows that using a planetary ball mill, we obtain a good yield of LaMg2Ni5Al4 compound after 5 h of mechanical alloying for both synthesis pathways. TEM analysis confirmed XRD results. SEM-EDX analysis of the final product was in agreement with the nominal chemical formula. A setup of possible solid-gaz hydrogenation reaction will be described so far at the end of this work. Electrochemical results demonstrate evidence on hydrogen absorption in the AB(3) material and the discharge capacity was equal to 5.9 H/f.u

Operando Electrochemical Liquid Cell Scanning Transmission Electron Microscopy Investigation of the Growth and Evolution of the Mosaic Solid Electrolyte Interphase for Lithium-Ion Batteries

The solid electrolyte interphase (SEI) is a key component of a lithium-ion battery forming during the first few dischage/charge cycles at the interface between the anode and the electrolyte. The SEI passivates the anode–electrolyte interface by inhibiting further electrolyte decomposition, extending the battery’s cycle life. Insights into SEI growth and evolution in terms of structure and composition remain difficult to access. To unravel the formation of the SEI layer during the first cycles, operando electrochemical liquid cell scanning transmission electron microscopy (ec-LC-STEM) is employed to monitor in real time the nanoscale processes that occur at the anode–electrolyte interface in their native electrolyte environment. The results show that the formation of the SEI layer is not a one-step process but comprises multiple steps. The growth of the SEI is initiated at low potential during the first charge by decomposition of the electrolyte leading to the nucleation of inorganic nanoparticles. Thereafter, the growth continues during subsequent cycles by forming an island-like layer. Eventually, a dense layer is formed with a mosaic structure composed of larger inorganic patches embedded in a matrix of organic compounds. While the mosaic model for the structure of the SEI is generally accepted, our observations document in detail how the complex structure of the SEI is built up during discharge/charge cycling

In Situ Electron Diffraction Tomography Using a Liquid-Electrochemical Transmission Electron Microscopy Cell for Crystal Structure Determination of Cathode Materials for Li-Ion batteries

International audienceWe demonstrate that changes in the unit cell structure of lithium battery cathode materials during electrochemical cycling in liquid electrolyte can be determined for particles of just a few hundred nanometers in size using in situ transmission electron microscopy (TEM). The atomic coordinates, site occupancies (including lithium occupancy), and cell parameters of the materials can all be reliably quantified. This was achieved using electron diffraction tomography (EDT) in a sealed electrochemical cell with conventional liquid electrolyte (LP30) and LiFePO4 crystals, which have a well-documented charged structure to use as reference. In situ EDT in a liquid environment cell provides a viable alternative to in situ X-ray and neutron diffraction experiments due to the more local character of TEM, allowing for single crystal diffraction data to be obtained from multiphased powder samples and from submicrometer- to nanometer-sized particles. EDT is the first in situ TEM technique to provide information at the unit cell level in the liquid environment of a commercial TEM electrochemical cell. Its application to a wide range of electrochemical experiments in liquid environment cells and diverse types of crystalline materials can be envisaged