The preparation of carbon-supported magnesium nanoparticles using melt infiltration

Magnesium dihydride contains 7.7 wt % hydrogen. However, its application for hydrogen storage is impeded by its high stability and slow kinetics. Bringing the size of Mg(H-2) into the nanometer range will not only enhance the reaction rates but has also been theoretically predicted to change the thermodynamic stability and destabilize the MgH2 with respect to Mg. However, the preparation of such small particles is a major challenge. We identified a method to prepare large amounts of nanometer-sized nonoxidized magnesium crystallites. The method is based on infiltration of nanoporous carbon with molten magnesium. The size of the Mg crystallites is directly influenced by the pore size of the carbon and can be varied from 2-5 to less than 2 nm. The majority of the nanocrystallites is not oxidized after preparation. No bulk magnesium was detected in the samples with nanoparticle loadings up to 15 wt % on carbon. These 3D supported nanomaterials present interesting systems to study how nanosizing and support interaction can steer the hydrogen sorption properties of metal hydrides.