MgH2Â +Â FeNb nanocomposites for hydrogen storage

Magnesium (magnesium hydride) nanocomposites have been widely investigated for hydrogen storage. As a general feature, these nanocomposites use high purity (expensive) catalysts to improve the hydrogen sorption kinetics of magnesium. In this manuscript we tested a low cost raw material (ferroniobium alloy) as catalyst for hydriding/dehydriding magnesium nanocomposites. The MgH2 + ferroniobium nanocomposites were synthesized by high-energy ball-milling and characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray microanalysis. The hydrogen absorption and desorption curves were measured in an automated Sieverts' type apparatus. We observed that ferroniobium alloy is an effective catalyst for hydrogen sorption, mainly with ferroniobium as coarse granulates. The hydrogen sorption behavior of MgH2 + ferroniobium nanocomposites was compared to those of Mg + high purity Nb, Fe or (Fe + Nb) catalysts. It was found that the high purity metals are slightly more active catalysts than ferroniobium alloy for hydrogen sorption in Mg. This behavior is discussed regarding the thermodynamic features of the catalyst/matrix nano-interfaces formed during ball-milling.