The Impact of Nanoporous Carbon on the Hydrogen Storage Properties of Light Metal Hydrides

Introduction Light metal hydrides are candidates for compact and efficient reversible on-board hydrogen storage. However, at the moment no known material fulfills all requirements regarding hydrogen content, release temperature, and reversibility simultaneously. Binary light metal hydrides generally are thermodynamically too stable, while in addition boronhydrides, alanates and other complex systems contain multiple phases upon dehydrogenation, causing reversibility issues due to phase segeagation. A general approach to the preparation of hydrogen storage materials is high energy ball milling, which decreases the crystallite size and allows the addition of catalysts. In an alternative approach, we study the effect of nanosizing the metal hydrides (<10 nm), and supporting or confining them in a porous matrix. This is not only expected to improve the kinetics, but can potentially also change the thermodynamics of the systems [1-3]. Furthermore, nanoconfinement can benefit the reversibility by limiting macroscopic phase segregation upon cycling [4], while the addition of carbon can also lead to better mechanical stability and thermal management. On the other hand the addition of a support or scaffold compromises the overall gravimetric hydrogen content of the material system. We investigate the effect of nanosizing light metal hydrides and supporting them on nanoporous carbon by melt infiltration. We demonstrated the impact on hydrogen sorption properties for several hydrides (NaAlH4, NaH, LiBH4 and MgH2) [5-9].