(100e) Fundamental Reactivity Analysis of Hydrogen Storage Materials

Hydrogen is seen as the future automobile energy source due to its increased efficiency over conventional means and its ready utilization in fuel cell applications. In searching for ever higher gravimetric and volumetric density hydrogen storage systems, it is inevitable that higher energy density materials will be used. To make safe and commercially acceptable condensed phase hydrogen storage systems, it is important to understand quantitatively the risks involved in using and handling these materials to develop appropriate risk mitigation strategies to handle unforeseen accidental events. This will allow for the identification of potential risks and implementation of risk mitigation strategies.

A rigorous set of environmental reactivity tests have been developed based on modified testing procedures codified by the United Nations for the transportation of dangerous goods. Potential hydrogen storage materials?2LiBH₄?MgH₂, NH₃BH₃, AlH₃, and 8LiH?3Mg(NH₂)₂?have been tested using these modified procedures to evaluate the relative risks of these materials coming in contact with the environment in hypothetical accident scenarios, including the identification of self-reactive substances, pyrophoric substances, and gas-emitting substances with water contact. An ignition event is most likely to occur if both a flammable concentration of hydrogen and sufficient thermal energy are available to ignite the hydrogen gas mixture. In order to predict hydride behavior for hypothesized accident scenarios, an idealized finite element model has been developed for a breached tank system resulting in dispersed hydride. Empirical thermodynamic calculations based on precise calorimetric experiments have been performed in order to quantify the energy and hydrogen release rates and to quantify the reaction products resulting from water and air exposure. Both thermal and compositional predictions have been made with respect to environmental scenarios identified as potential ignition events.