Maxence VINCENT
defended his PhD thesis
on 8 december 2025
Study of Al−N−H compounds derived from ammonia alane by solid-state NMR spectroscopy:
methodological synthesis, thermolysis mechanisms and prospects for rehydrogenation
In front of the jury:
Sara CAVALIERE, Professeure des universités, Université de Montpellier – Examinatrice
Christel GERVAIS, Professeure des universités, Université Sorbonne – Rapporteuse
Bérangère TOURY, Professeure des universités, Université Claude Bernard Lyon 1 – Rapporteuse
Thibault CHARPENTIER, Directeur de recherche, NIMBE CEA Saclay – Invité
Umit B. DEMIRCI, Professeur des universités, Université de Montpellier – Directeur de thèse
Raphaël JANOT, Chargé de recherche CNRS, Université de Picardie Jules Verne – Co-directeur de thèse
Abstract:
This thesis is part of the development of new chemical hydrogen carriers and initially focused on ammonia alane (AlH3NH3), a compound with a high gravimetric hydrogen capacity of 12.86 wt%. As the work progressed, the research shifted towards a more fundamental approach, aiming to identify and characterize Al−N−H compounds, which remain scarcely documented in the literature.
We explored and optimized three synthetic routes: metathesis/dehydrogenation, cryo-milling, and Lewis acid–base reaction, which enabled us to obtain a diversity of samples representative of this chemistry. The study generated a rich set of solid-state NMR MAS data, including 1H, 7Li, 15N, and 27Al nuclei. Advanced experiments (MQMAS, HETCOR, CPMAS, REDOR) were performed, with highly reliable and detailed deconvolutions from the MQMAS, enabling precise quantification of aluminum environments and investigation of the effect of temperature on NMR parameters and, consequently, on the molecular structure. These results were complemented by infrared spectroscopy combined with DFT calculations and X-ray photoelectron spectroscopy (XPS).
Thermal treatments led to the formation of Al−N−H polymers, including polyaminoalane, polyiminoalane, and intermediate polymers, resulting in amorphous phases. Thermogravimetric analyses coupled with mass spectrometry (TGA-MS) revealed hydrogen and ammonia release, providing initial insights into decomposition mechanisms.
Overall, this work establishes a baseline of experimental results and structural knowledge on Al−N−H materials, opening the way to further fundamental studies as well as potential applications in hydrogen storage.s et de données expérimentales sur les composés Al−N−H, fournissant des éléments structuraux et mécanistiques essentiels à la compréhension de cette famille de composés.
