(100f) Environmental Reactivity of Solid-State Hydrogen Storage Systems: Fundamental Testing and Evaluation

There is
extensive research being conducted in developing new hydrogen storage systems
that have higher gravimetric and volumetric capacities.  However, less is
understood about the hazards and risks associated with using and handling these
materials.  Therefore, it is critical to develop appropriate risk mitigation
strategies to handle unforeseen events such as a breach-of-tank scenario in
order to design commercially safe condensed phase hydrogen storage systems.  A
crucial aspect in risk identification is the development of rigorous
environmental reactivity testing standards and procedures.   One way to
accomplish this is by adopting a modified testing approach from the United
Nations¹ testing procedure for the transportation of dangerous goods
to evaluate a potential hydrogen storage material reactivity to air and water. 
The modified U.N. procedures include identification of self-reactive,
pyrophoric, and gas-emitting substances with water contact.  The results of
these tests for air and water contact sensitivity will be compared for such
hydrogen storage candidates as 2LiBH₄·MgH₂, NH₃BH₃,
8LiH·3Mg(NH₂)₂, and AlH₃.  The water contact
tests are divided into two scenarios dependent on the hydride to water mole
ratio and heat transport characteristics.  Air contact tests were conducted to
determine whether a substance will spontaneously react with air in a packed or
dispersed form. 

Additionally, thermodynamic calculations and substantiating
calorimetric experiments were performed in order to quantify the energy
released, energy release rates and to quantify the reaction products resulting
from water and air exposure of various solid state systems.  These calorimetric
measurements, performed on the ?small scale?, were compared with standardized United
Nations (UN) based tests for air and water reactivity and used to develop
quantitative kinetic expressions for hydrolysis and air oxidation in these
systems.  Furthermore, insight gained from these U.N. tests as well as
isothermal calorimetry will allow the formulation of additional tests geared
toward safety engineering, numerical simulation, and integration.

¹ DOT/UN
Doc., Recommendations on the Transport of Dangerous Goods, Manual of Tests
and Criteria, 3rd Revised Ed., ISBN 92-1-139068-0, (1999).