Publications by authors named "Domitille Giaume"

High-energy-density lithium-rich materials are of significant interest for advanced lithium-ion batteries, provided that several roadblocks, such as voltage fade and poor energy efficiency are removed. However, this remains challenging as their functioning mechanisms during first cycle are not fully understood. Here we enlarge the cycling potential window for LiNiMnCoO electrode, identifying novel structural evolution mechanism involving a structurally-densified single-phase A' formed under harsh oxidizing conditions throughout the crystallites and not only at the surface, in contrast to previous beliefs. We also recover a majority of first-cycle capacity loss by applying a constant-voltage step on discharge. Using highly reducing conditions we obtain additional capacity via a new low-potential P" phase, which is involved into triggering oxygen redox on charge. Altogether, these results provide deeper insights into the structural-composition evolution of LiNiMnCoO and will help to find measures to cure voltage fade and improve energy efficiency in this class of material.

Electroreduction of CO to CO is one of the simplest ways to valorise CO as a source of carbon. Herein, a cheap, robust, Cu-based hybrid catalyst consisting of a polymer of Cu phthalocyanine coated on carbon nanotubes, which proved to be selective for CO production (80 % faradaic yield) at relatively low overpotentials, was developed. Polymerisation of Cu phthalocyanine was shown to have a drastic effect on the selectivity of the reaction because molecular Cu phthalocyanine was instead selective for proton reduction under the same conditions. Although the material only showed isolated Cu sites in phthalocyanine-like CuN coordination, in situ and operando X-ray absorption spectroscopy showed that, under operating conditions, the Cu atoms were fully converted to Cu nanoparticles, which were likely the catalytically active species. Interestingly, this restructuring of the metal sites was reversible.

Recently, Ir -based perovskite-like materials were proposed as oxygen evolution reaction (OER) catalysts in acidic media with promising performance. However, iridium dissolution and surface reconstruction were observed, questioning the real active sites on the surface of these catalysts. In this work, Sr MIr O (M=Fe, Co) and Sr Fe Ir O were explored as OER catalysts in acidic media. Their activities were observed to be roughly equal to those previously reported for La LiIrO or Ba PrIrO . Coupling electrochemical measurements with iridium dissolution studies under chemical or electrochemical conditions, we show that the deposition of an IrO layer on the surface of these perovskites is responsible for their OER activity. Furthermore, we experimentally reconstruct the iridium Pourbaix diagram, which will help guide future research in controlling the dissolution/precipitation equilibrium of iridium species for the design of better Ir-based OER catalysts.

Alloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, such a strategy is used to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO versus H reduction. By varying the Zn/Cu ratio, tailored syngas mixtures are obtained without the production of other gaseous products, which is attributed to preferential CO- and H -forming pathways on the alloys. The syngas ratios are also significantly less sensitive to the applied potential in the alloys relative to pure metal equivalents; an essential quality when coupling electrocatalysis with renewable power sources that have fluctuating intensity. As such, industrially relevant syngas ratios are achieved at large currents (-60 mA) for extensive operating times (>9 h), demonstrating the potential of this strategy for fossil-free fuel production.

To design novel layered materials, bottom-up strategy is very promising. It consists of (1) synthesizing various layered oxides, (2) exfoliating them, then (3) restacking them in a controlled way. The last step is based on electrostatic interactions between different layered oxides and is difficult to control. The aim of this study is to facilitate this step by predicting the isoelectric point (IEP) of exfoliated materials. The Multisite Complexation model (MUSIC) was used for this objective and was shown to be able to predict IEP from the mean oxidation state of the metal in the (hydr)oxides, as the main parameter. Moreover, the effect of exfoliation on IEP has also been calculated. Starting from platelets with a high basal surface area over total surface area, we show that the exfoliation process has no impact on calculated IEP value, as verified with experiments. Moreover, the restacked materials containing different monometallic (hydr)oxide layers also have an IEP consistent with values calculated with the model. This study proves that MUSIC model is a useful tool to predict IEP of various complex metal oxides and hydroxides.

Luminescent inorganic nanoparticles are now widely studied for their applications as biological probes for in vitro or in vivo experiments. The functionalization of the particles is a key step toward these applications, since it determines the control of the coupling between the particles and the biological species of interest. This paper is devoted to the case of rare earth doped oxide nanoparticles and their functionalization through their surface encapsulation with a functional polysiloxane shell. The first step of the process is the adsorption of silicate ions that will act as a primary layer for the further surface polymerization of the silane, either aminopropyltriethoxysilane (APTES) or glycidoxypropyltrimethoxysilane (GPTMS). The amino- or epoxy- functions born by the silane allow the versatile coupling of the particles with bio-organic species following the chemistry that is commonly used in biochips. Special attention is paid to the careful characterization of each step of the functionalization process, especially concerning the average number of organic functions that are available for the final coupling of the particles with proteins. The surface density of amino or epoxy functions was found to be 0.4 and 1.9 functions per square nanometer for GPTMS and APTES silanized particles, respectively. An example of application of the amino-functionalized particles is given for the coupling with alpha-bungarotoxins. The average number (up to 8) and the distribution of the number of proteins per particle are given, showing the potentialities of the functionalization process for the labeling of biological species.

We used lanthanide-ion doped oxide nanoparticles, Y(0.6)Eu(0.4)VO(4), as donors in fluorescent resonance energy transfer (FRET) experiments. The choice of these nanoparticles allows us to combine the advantages of the lanthanide-ion emission, in particular the long lifetime and the large Stokes shift between absorption and emission, with the detectability of the nanoparticles at the single-particle level. Using cyanine 5 (Cy5) organic molecules as acceptors, we demonstrated FRET down to the single-nanoparticle level. We showed that, due to the long donor lifetime, unambiguous and precise FRET measurements can be performed in solution even in the presence of large free acceptor concentrations. Highly efficient energy transfer was obtained for a large number of acceptor molecules per donor nanoparticle. We determined FRET efficiencies as a function of Cy5 concentration which are in good agreement with a multiple acceptor-multiple donor calculation. On the basis of the donor emission recovery due to acceptor photobleaching, we demonstrated energy transfer from single-nanoparticle donors in fluorescence microscopy experiments.