Author/Authors :
Gross, Adam F HRL Laboratories, LLC, USA , Ahn, Channing C California Institute of Technology - Division of Engineering and Applied Science, USA , Van Atta, Sky L HRL Laboratories, LLC, USA , Liu, Ping HRL Laboratories, LLC, USA , Vajo, John J HRL Laboratories, LLC, USA , Vajo, John J California Institute of Technology - Division of Engineering and Applied Science, USA
Abstract :
Nanoparticles of MgH2 incorporated in a mesoporous carbon aerogel demonstrated accelerated hydrogen exchange kinetics but no thermodynamic change in the equilibrium hydrogen pressure. Aerogels contained pores from 2 to ~30 nm in diameter with a peak at 13 nm in the pore size distribution. Nanoscale MgH2 was fabricated by depositing wetting layers of nickel or copper on the aerogel surface, melting Mg into the aerogel, and hydrogenating the Mg to MgH2. Aerogels with metal wetting layers incorporated 9–16 wt% MgH2, while a metal free aerogel incorporated only 3.6 wt% MgH2. The improved hydrogen sorption kinetics are due to both the aerogel limiting the maximum MgH2 particle diameter and a catalytic effect from the Ni and Cu wetting layers. At 250 °C, MgH2 filled Ni decorated and Cu decorated carbon aerogels released H2 at 25 wt% h−1 and 5.5 wt% h−1, respectively, while a MgH2 filled aerogel without catalyst desorbed only 2.2 wt% h−1 (all wt% h−1 values are with respect to MgH2 mass). At the same temperature, MgH2 ball milled with synthetic graphite desorbed only 0.12 wt% h−1, which demonstrated the advantage of incorporating nanoparticles in a porous host
