Researchers from the Pacific Northwest National Laboratory (PNNL) and Rohm and HAAS have determined that ammonia borane (AB) is a promising hydrogen storage material for fuel-cell vehicle applications due to its high hydrogen density and stability under typical ambient conditions.
Ammonia borane is a stable solid at room temperature that requires heating to near 100° C to release the hydrogen. PNNL had earlier found that ammonia borane (NH3BH3) and polyammonia borane (-NH2BH2-) within a scaffold of mesoporous silica templates demonstrated hydrogen storage capacities of > 12 wt.%. (Earlier post.)
There have been concerns over the materials stability in warm temperatures—for example, in a car parked in the hot sun.
PNNL and Rohm and HAAS Company researchers measured the thermal stability of the solid material from 40° C to 60° C, and assessed hydrogen release from 70° C to 90° C.
The experiments and calculations both indicate that the stability of ammonia borane relates to its purity and that it can remain stable for many days or longer in high temperatures. The research is also helping to determine if auxiliary cooling is required to minimize the inadvertent release of hydrogen in the tank and keep the vehicle safe.
Scott Rassat from PNNL presented the results at the 232nd National Meeting of the American Chemical Society in San Francisco.