Liquid Phase-Made Aluminum Nanoparticles and Their Hydrogen Sorption as Aluminum/LiH Composite

Aluminum nanoparticles, Al(0), are prepared in toluene at room temperature (25 °C) by reduction of AlH 3 with dilithium naphthalenide ([Li 2 Naph]). To dissolve the starting materials in toluene, AlH 3 and [Li 2 Naph] are coordinated by N, N, N ′, N ′-tetramethylethylendiamin (TMEDA). The as-prepared Al(0) nanoparticles are monocrystalline and exhibit a uniform size of 11 ± 3 nm with narrow size distribution. They are highly reactive, as indicated by reaction in air and even with nitrogen. Besides the formation of Al(0) nanoparticles, the [Li 2 Naph]-driven reduction of AlH 3 results in the formation of LiAlH 4 as a side phase, which can be removed but is difficult to remove due to its low solubility in solvents that do not react with the Al(0) nanoparticles (e.g., toluene, THF). The presence of LiAlH 4 and the formation of a Al(0) nanoparticle/LiAlH 4 composite, however, turned out to be advantageous in regard to H 2 sorption. After thermal transition of LiAlH 4 to LiH (250 °C, vacuum), the resulting Al(0) nanoparticle/LiH composite shows promising H 2 sorption and H 2 uptake at 250 °C and 100 bar of H 2 with a gravimetric capacity of 3.8%. After modification of the Al(0) nanoparticles with 1 wt % Pd for activation, the H 2 uptake occurs at even a reduced temperature of 150 °C.