Environmental reactivity of solid-state hydrogen storage systems: Fundamental testing and evaluation

In order to enable the commercial acceptance of solid-state hydrogen storage materials and systems it is important to understand the risks associated with the environmental exposure of various materials. In some instances, these materials are sensitive to the environment surrounding the material and the behavior is unique and independent to each material. The development of testing procedures to evaluate a material’s behavior with different environmental exposures is a critical need. In some cases material modifications may be needed in order to reduce the risk of environmental exposure. We have redesigned two standardized UN tests for clarity and exactness; the burn rate and self-heating tests. The results of these and other UN tests are shown for ammonia borane, NH3BH3, and alane, AlH3. The burn rate test showed a strong dependence on the preparation method of aluminum hydride as the particle size and trace amounts of solvent greatly influence the test results. The self-heating test for ammonia borane showed a failed test as low as 70 °C in a modified cylindrical form. Finally, gas phase calorimetry was performed and resulted in an exothermic behavior within an air and 30%RH environment.

► Dry and humid air exposure studies were conducted on potential hydrogen storage materials ammonia borane and alane to assess the risk of their exposure to the environment.
► Alane is susceptible to vigorous reaction in humid air.
► Synthesis techniques of alane affecting particle size impacted the environmental exposure results with smaller particles being more active.
►  Ammonia borane is relatively stable at ambient conditions in air but subject to self-heating and hydrogen release if heated above 70 °C.
► Both alane and ammonia borane are susceptible to burning with subsequent release of hydrogen when exposed to an open flame.