A New Metal-Decorated Carbon Catalyst for Dehydrogenation of Complex Hydride Hydrogen Storage Materials
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In recent years, many new solid-state hydrides with a high hydrogen capacity that meet DOE requirement (> 7.5 wt.% H2) have been synthesized as promising on-board hydrogen storage materials. In these hydrides, however, only a small fraction of hydrogen can be released at a desired on-board operating temperature (4 as a test case. Dehydrogenation of NaAlH4 can be greatly facilitated by activated carbon catalysts. The catalytic function can be further enhanced by decorating the carbon with Co, Ni, or Cu nanoparticles. The decomposition temperature was lowered by as much as 100°C using a 3 wt.% Co or Ni-decorated activated carbon, comparable to a Ti-based catalyst, which were the most effective among the metals tested. The catalytic effect is likely due to a combination of hydrogen spillover effect, high contact area between carbon and the hydride, and confinement of the hydride as nano-sized domains in the pores of the carbon matrix. The catalysts were also effective in facilitating rehydrogenation of NaAlH4 under moderate pressure (75.8 bar H2) and low temperature (120°C), when no rehydrogenation would occur without the catalyst. The fact that this new catalyst system is not specific to any hydride offers many potential applications.