Hydrogen storage properties of hydrogenated graphite destabilized by mixing with lithium hydride

Hydrogen storage properties of the ball-milled mixtures composed of hydrogenated nano-structural graphite (CnanoHx) and lithium hydride (LiH) were examined from thermodynamic and structural points of view, where the CnanoHx was synthesized by ball-milling graphite powder under hydrogen atmosphere. Since hydrogen atoms in the CnanoHx and LiH are strongly bonded with each host atom, heating up to >600°C is necessary to release hydrogen from each solid product. The CnanoHx and LiH composites desorbed hydrogen and hydrocarbon gases below 400°C with about 9.4 mass% weight loss. The 2: 1 composite of the CnanoHx and LiH reversibly stored hydrogen with an effective capacity of about 4.5 mass % at 350°C. No evident peaks were observed in XRD profiles after the dehydrogenation, indicating that the nano-structural feature remained after dehydrogenation due to formation of (CLi) nano clusters. However, only the LiH phase was crystallized after rehydrogenation at 350°C. From these results, it is concluded that hydrogen in the composites is destabilized by a novel interaction between the CnanoHx and LiH in a nanometer scale, and is desorbed at lower temperatures than each of the components. Therefore, this Li-C-H system can be recognized to be a new family of hydrogen storage materials.