Halide-free Grignard reagents for the synthesis of superior MgH2 nanostructures

Grignard reagents can provide a simple path to generate, through their thermal decomposition, magnesium (Mg) and/or its hydride (MgH₂). However, existing compounds lack the ability to lead to “adequate” MgH₂ structures to enable effective hydrogen storage. Herein, we report on the possibility to tune Grignard reagent's chemical structure, i.e. number of β-hydrogen, and the activation energy for their thermal decomposition to lead to Mg/MgH₂. For example, di-tert-butylmagnesium with nine β-hydrogen was able to decompose at a very low temperature of 167 °C to generate MgH₂/Mg, which is 100 °C lower than the temperature required to generate MgH₂ from di-n-butylmagnesium, i.e. the only compound known to date. More remarkably, the MgH₂ synthesized from the di-tert-butylmagnesium precursor was able to release hydrogen from 100 °C. These promising hydrogen storage properties are credited to the formation of the metastable γ-MgH₂ phase, which is believed to result from the structural defects generated upon the thermal decomposition of di-tert-butylmagnesium.