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

Abstract

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.