Résumé
Hydrogen (H2) is emerging as a crucial energy alternative for the coming decades. Focusing on its extraction from gas mixtures, this work reports on a novel strategy for manufacturing H2-selective ultramicroporous carbon-doped alumina membranes using Molecular Layer Deposition (MLD). The membranes were synthesized on commercial γ-alumina tubular supports using trimethylaluminum and ethylene glycol, forming a conformal hybrid organic-inorganic layer of alucone. The final porous structure of the membrane was induced and tuned via a thermal treatment, which converted the alucone into porous C-doped alumina. The influence of the thermal treatment conditions on the physicochemical characteristics and performance of the as-formed alumina membrane layer was investigated in details. Gas permeation measurements revealed an ultramicroporous membrane network, characterized by a dominant molecular sieving mechanism. This led to separation factors of 242 and 150 for the H2/CH4 and H2/N2 gas pairs respectively, measured at 126°C in quaternary gas mixtures containing CO2. Furthermore, the microporous nature of the membrane was confirmed by calculating the activation energies for each tested gas. The results presented demonstrate the potential of MLD in synthesizing H2-selective porous alumina membranes with competitive performance at relatively low operating temperatures. Additionally, this strategy could be applied to create membranes selective for other gas mixtures by carefully tuning the material porous structure. These microporous thin films could also serve as protective barriers against poisoning species or as selective layers to enhance gas sensors selectivity.