Catalytical Synthesis and In Situ Doping of Sodium Aluminum Hydride from Elements

Abstract

Sodium aluminum hydride (NaAlH 4 ) is a prominent hydrogen storage material and a cost-effective substitute for LiAlH 4 . For industrial application as a hydrogen store in the medium-temperature range, efficient preparation methods for NaAlH 4 are required. We report here a feasible approach to prepare pure and in situ doped NaAlH 4 from its constituent elements, namely Na, Al, and H 2 . Formation of NaAlH 4 was realized by ball milling sodium lumps and aluminum powders of commercial grade in tetrahydrofuran followed by hydrogenation under moderate conditions in an autoclave. Metal chlorides CeCl 3 and TiCl 4 as well as a zero-valent Ti prepared in this work were used as catalysts for the synthesis of NaAlH 4 . The removal of the solvent after hydrogenation resulted in in situ doped NaAlH 4 for hydrogen storage utilization, which exhibits excellent storage properties, whereas pure NaAlH 4 was obtained by separation of the catalysts through filtration.