Perspectives and Challenges for Solid State Hydrogen Storage in Automotive Applications

The present review of the most recent patents outlines the progress made over the last five years in the search of novel materials and processes that might allow large amounts of hydrogen to be stored on board of vehicles. Worth of note are the results of certain ab-initio calculations proving that some compounds not yet synthesized might, actually, show features approaching the requirements of the US Department of Energy. Significant progress has been made concerning the absorption/desorption reversibility of Li-N-H compounds (amides/imides, LiH, Li3N), borohydrides and boranes. These materials, at the actual state of the art, appear still largely inadequate to comply with DOE targets. However, their intrinsic high mass capacity offers wide margin for further research in this area. The achievements made with alanates, magnesium-based hydrides and bcc-alloy hydrides, although of great significance from a point of view of the fundamental research, nonetheless, appear to be of limited impact from a practical point of view, at least for automotive applications. This is mainly due to the relatively low intrinsic mass capacity of these materials.