Missions

In this thesis project, we will focus on understanding the charge distribution (e⁻/H⁺) within POMs during their super-reduction process in organic media. This first phase will be based on an approach combining: i) multi-scale characterizations, including spectroscopic studies (NMR, EPR, UV-Vis) and, where possible, X-ray diffraction analyses carried out in the laboratory, ii) EXAFS/XANES measurements carried out on the ROCK beamline at the SOLEIL synchrotron, and iii) theoretical studies (DFT, TD-DFT, and CASSCF). This first part of the project will establish structure-property relationships essential to identify the most promising POMs as electron and proton reservoirs. This work will provide a solid basis for the integration of super-reduced POMs into flow batteries, whose performance optimization will be carried out in collaboration. Furthermore, the expertise acquired in the synthesis and manipulation of these super-reduced POMs will open the way to the exploration of their reactivity, particularly in the context of transfer hydrogenation reactions, thus offering new perspectives for energy conversion.

Activités

The doctoral student will be responsible for studying the reduction processes of polyoxometalates, characterizing the super-reduced species (chemistry under inert atmosphere) using analytical tools available in our laboratory (single-crystal X-ray diffraction, multinucleus NMR, electrochemistry, UV-vis, RAMAN, TGA, IR and ICP), but also using synchrotron radiation (XANES/EXAFS, SAXS or serial crystallography). In addition, the doctoral student will study the reactivity of new synthesized species (hydrogenation reactions).

Compétences

• Strong interest in experimental laboratory work
• Motivation and passion for fundamental sciences
• Scientific rigor, dynamism, adaptability, and team spirit

Contexte de travail

The development of efficient electrochemical energy storage and conversion solutions is becoming a priority to mitigate the adverse effects associated with the intermittency of renewable energy. Unlike traditional batteries that store energy in solid electrodes, flow batteries rely on liquid electrolytes containing two soluble electroactive species, making them particularly suitable for stationary applications subject to fluctuations in energy production. To ensure their efficiency and commercial viability, it is essential to design electrolytes capable of storing high energy density.
The approach proposed in this thesis project aims to exploit the exceptional properties of polyoxometalates (POMs), electroactive inorganic polyanions composed of V, Mo, and W. These entities, endowed with unparalleled structural diversity in terms of composition, shape, and size, are obtained by acidification of metalate ions in aqueous solution and are widely studied in diverse fields such as energy, health, environment, and quantum technologies. Furthermore, super-reduced POMs, capable of accumulating large numbers of electrons and protons (two electrons/protons per metal center), could serve as redox mediators to carry out chemical transformations within decoupled electrolysis devices. Thus, the reactivity of super-reduced POMs could be exploited for on-demand transfer hydrogenation reactions, offering a promising solution for the manipulation of dihydrogen.
This doctoral contract will be funded by the CNRS 'Mission for Transverse and Interdisciplinary Initiatives".

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.