PH'D defence M Konakpo Parfait Kamara

Abstract : With the aim of decarbonizing its energy mix and lowering its CO2 emissions, France has decided to invest massively in the decarbonized production of hydrogen as an energy carrier for mobility and stationary applications [1]. Of the one million ton of hydrogen produced in France, 96% is produced by steam reforming of hydrocarbons. France's strategy is to develop the hydrogen sector by investing in the installation of electrolyzers. What's more, the latest discoveries of huge deposits of natural hydrogen (46 million tons of hydrogen in Lorraine) are creating enthusiasm and expanding the field of prospects. [2]. Another decarbonated hydrogen production sector that is less talked about is the biological sector, which offers great potential for diversifying production routes. Hydrogen from these sources raises the question of its quality for use in mobility or stationary fuel cell systems.
The aim of this thesis is to define strategies for the use of bio-hydrogen or natural hydrogen using proton exchange membrane fuel cell (PEMFC) technology, from hydrogen production to electrochemical conversion.
The first part consisted in studying the impact of impurities or diluents (N2, Ar, He, CH4, CO2) contained in hydrogen from biological and native processes in a half-cell (gas diffusion electrode, GDE). This study was then extended to a single-cell proton exchange membrane fuel cell. Finally, a laboratory-scale biological reactor was used to produce hydrogen from organic sources by photo fermentation (PF), which was then tested in a GDE. Several electrochemical and physicochemical characterization techniques, such as cyclic voltammetry, chrono amperometry, CO stripping for electroactive surface measurement, scanning and transmission electron microscopy, ion chromatography, etc., were used to assess the performance of the PEMFC fed by bio-hydrogen, and its impact on fuel cell components.
The results of the electrode activity for the hydrogen oxidation reaction in GDE revealed mass-transport limitation effects for the mixtures, with a particular behavior observed for the nitrogen mixture, and the methane and carbon dioxide mixtures, which in addition to dilution have a carbon monoxide poisoning effect on the electrode.
Next, single-cell tests using H2/Ar, H2/N2 and H2/CO2 mixtures at 30 and 40% H2 by volume for stationary applications revealed greater performance losses for the carbon dioxide mixture, while the argon and nitrogen mixtures performed almost equally well. These performance losses are due to electroactive surface losses.
Finally, the production of biohydrogen by PF showed that the choice of biomass, pre-treatment and bacterial strain influenced the quality of the biogas produced and the electrochemical performances obtained from it without purification steps.
References
[1] « Présentation de la stratégie nationale pour le développement de l’hydrogène décarboné en France ». Consulté le: 11 janvier 2024. [En ligne]. Disponible sur: https://www.economie.gouv.fr/presentation-strategie-nationale-developpement-hydrogene-decarbone-france
[2] « Le plus gros gisement d’hydrogène naturel du monde vient d’être découvert en France », SudOuest.fr. Consulté le: 11 janvier 2024. [En ligne]. Disponible sur: https://www.sudouest.fr/economie/energie/le-plus-gros-gisement-d-hydrogene-naturel-du-monde-vient-d-etre-decouvert-en-france-17826239.php