Résumé
Proton exchange membrane fuel cells (PEMFCs) are promising devices for energy production, but one of the main limitations of conventional PEMFCs is the use of large amounts of critical materials at the cathode. In this work, we aim to replace platinum with a redox molecule that must be able to be electrochemically reduced at the cathode and exhibit fast chemical oxidation kinetics under oxygen in an external regenerator. As a conventional fuel cell, at the anode, dihydrogen is oxidized into protons (1).The absence of platinum at the cathode helps reduce costs while improving the physical and chemical stability of the membrane due to the maintenance of its hydration and the absence of reactive radicals nearby.This study focuses on the development of an unconventional proton exchange membrane fuel cell (PEMFC) incorporating a redox flow at the cathode, transforming the PEMFC into a chemically regenerative redox fuel cell (CRRFC). More precisely, we study different redox mediators and their electrochemical properties. The main challenge is to select the appropriate redox mediator for the system which must meet several criteria, including rapid oxidation by dioxygen, a high redox potential, and fast electron transfer kinetics, while also providing high chemical stability and solubility in acidic media.We selected and characterized multiple organometallic complexes with high oxidation potentials, specifically for their potential use as redox mediators in CRRFCs. This study focuses mainly on iron-based complexes with different chelating ligands (2),to modify the physicochemical properties of the mediators in order to meet the specific requirements of the system.These mediators have been tested in a fuel cell, and their performance has been compared based on their redox potential, reversibility, solubility, and compatibility with an acidic environment. This study offers perspectives to guide future improvements of these organometallic compounds in energy conversion applications.AcknowledgementThis work was carried within the framework of the collaboration between MFP Michelin (Manufacture Française des Pneumatiques Michelin), région Occitanie, the CNRS (Centre National de Recherche Scientifique), University of Montpellier and ENSCM within the HydrogenLab. References Bacabe, P.-Y. Blanchard; International Journal of Hydrogen Energy. 2024, 657-665.Gao, M. J. Aziz; Advanced Energy Materials, 2022, 2202444