LITHIUM-CARBON-HYDROGEN SYSTEMS AS A NOVEL FAMILY OF HYDROGEN STORAGE MEDIA

摘要

Hydrogen storage properties of ballmilled mixtures composed of the hydrogenated nano-structured carbon (C~(nano)H_x) and lithium hydride (LiH) were examined by thermal and optical spectroscopic analyses. LiH needs higher temperature than 600℃ for hydrogen desorption even under vacuum condition, while C~(nano)H_x, which was mechanochemically synthesized from graphite powder by ballmilling under hydrogen atmosphere, reveals hydrogen and hydrocarbons desorption in wide temperature range from 300 to 800℃. Nevertheless, the composite of C~(nano)H_x and LiH prepared by ballmilling desorbs hydrogen in relatively lower temperature range from 150 to 450℃. These phenomena indicate that the thermally liberated hydrocarbon radicals immediately react with LiH and release hydrogen instead of hydrocarbons emission, because C~(nano)H_x contains hydrocarbon groups at the edge of nano-meter sized graphenes, which are recognized as IR active C-H stretching mode, and LiH is well-known as an ionic crystal. Furthermore, it is of interest that a nanostructural feature persists in this composite even after annealing at 350℃, which shows excellent cycle properties as hydrogen storage media.