Nouveaux matériaux électrocatalytiques pour la conversion d'énergie grâce à l'analyse combinée d'objets individuels.

par Olivier Henrotte

Projet de thèse en Chimie

Sous la direction de Bruno Jousselme.

Thèses en préparation à Paris Saclay , dans le cadre de Sciences Chimiques : Molécules, Matériaux, Instrumentation et Biosystèmes , en partenariat avec NIMBE - Nanosciences et Innovation pour les Matériaux la Biomédecine et l'Énergie (laboratoire) , Laboratoire Innovation en Chimie de Surface Et Nanosciences (equipe de recherche) et de Université Paris-Sud (établissement de préparation de la thèse) depuis le 01-10-2015 .


  • Résumé

    L'avenir de notre approvisionnement en énergie dépend de notre capacité à innover dans la mise au point de systèmes de conversion et de stockage de l'énergie. Dans ce domaine, les matériaux électrocatalytiques sont la pierre angulaire de nombreux défis -en particulier pour les piles à combustible- car ils offrent des solutions adaptées pour effectuer efficacement des réactions chimiques complexes. Le projet introduit et met en œuvre une nouvelle stratégie s'appuyant sur la microscopie électrochimique pour trouver de nouvelles briques élémentaires à bas coût, entre autre à base des feuillets d'oxyde de graphène réduits: l'analyse combinée de nanoobjets va permettre de trouver de nouvelles espèces électrocatalytiques, d'optimiser la composition des matériaux et les conditions de mise en forme, et de comprendre l'origine du vieillissement des couches fonctionnelles. Le projet permettra au final de proposer des dispositifs ayant des performances améliorées.

  • Titre traduit

    Finding new electrocatalytic materials for energy conversion through a combined analysis of individual objects.


  • Résumé

    Electrocatalytic materials offer suitable solutions for performing very complex reactions useful for energy conversion devices such as fuel cells. These systems need to respond to three main characteristics: sustainability, cost-effectiveness and stability. Hence, large efforts worldwide are currently devoted to finding highly efficient electrocatalytic layers for reactions such as oxygen reduction, hydrogen evolution, or carbon dioxide reduction, with low cost materials and long life duration. An electrocatalytic layer is a three dimensional electrode that has to perform simultaneously many tasks: the catalysed charge transfer, of course, but also the transport of reactants and products through the different parts of the system. Because of their multifunctional nature, electrocatalytic layers are inhomogeneous aggregates of multiple components: carbon additive, binder, pores filled with electrolyte… in addition to the electrocatalyst. Unfortunately, the response of elementary bricks embedded into a complex layer is distorted by unequal accessibility (both chemical and electrical) within this composite material. Nowadays, the complexity of the systems, and the diversity of the approaches have reached such an extent that the finding of more efficient energy converting systems is presently very empirical, hindered by the lack of appropriate electroanalytical methods to identify precisely the most performant elementary bricks. The present project introduces and uses a new strategy for assessing elementary bricks through the in situ analysis of individual objects used to form electrocatalytic layers. It will permit to find new electrocatalytic species, optimise the material composition and processing conditions, and understand the origin of its ageing. This will lead to electrocatalytic materials having improved performances. The objective of the project is thus both to produce fundamental knowledge useful for the energy transition, and to find new materials, methods and processes that will be integrated into various technologies related to energy. Among others, these systems are essential for the hydrogen sector, a field that offers important perspectives both for the economy and the environment. The project involves a combined analysis of individual objects using among others Scanning Electrochemical Microscopy (SECM). The SECM technique permits to obtain electrochemical images of substrates through in situ, localized, and contactless measurements. It requires the displacement of a micro- or nano-electrode near a surface of interest. SECM offers two major advantages that makes it a particularly suitable technique for the fulfilment of our objectives: (i) high-standard commercial set-ups, associated with emerging nanoprobe fabrication methods will permit to achieve very high spatial resolutions (few ten of nanometers) and sensitivity (~pA). This has permitted an exponential development of nanoscale SECM and SECM variants. (ii) SECM measurements are highly reproducible, and the physicochemical principles at the basis of the measurement can be quantitatively reproduced with models. With the help of numerical simulation, an accurate link between the measured quantities and the parameters of interest is thus possible. It is worth mentioning that combining SECM experiments with numerical simulation is precisely an active research theme at LICSEN.