Phase-structural and morphological features, dehydrogenation/re-hydrogenation performance and hydrolysis of nanocomposites prepared by ball milling of MgH₂ with germanium

Ball milling of magnesium hydride with germanium additives in argon for up to 10 h was shown to result in the formation of nanocomposites of α- and γ-modifications of MgH₂ together with individual Ge phase. When the as milled samples are heated-up, Ge interacts with MgH₂ to form Mg₂Ge at T = 350–400 °C; the phase transformation overlaps with MgH₂ decomposition and Mg₂Ge phase remains in the material after its re-hydrogenation at T = 300 °C and P(H₂)∼15 bar. The ball milled Ge-MgH₂ nanocomposites were found to be characterised by an improved hydrogen release via hydrolysis in organic acid solutions as compared to pure MgH₂ prepared and tested at the same conditions. It was found that the composite containing 5 wt% of Ge and ball milled for 5 h showed the best hydrogen generation performance, with total hydrogen release exceeding 1.55 NL/g (yield close to 100%) in one minute.