Catalytic Effect of Boric Acid On Thermal Dehydrogeantion of Ammonia Borane

Ammonia borane (AB, NH₃BH₃) is a promising hydrogen storage material for use in proton exchange membrane (PEM) fuel cell applications. In this study, the effect of boric acid on AB dehydrogenation was investigated. Our study shows that boric acid is a promising additive to decrease onset temperature as well as to increase hydrogen release kinetics for AB thermolysis. Using boric acid, we obtained high H₂ yield (11.5 wt% overall H₂ yield, 2.23 H₂ equivalent) at 85°C, PEM fuel cell operating temperatures, along with rapid kinetics. In addition, only trace amount of NH₃ (20-30 ppm) was detected in the gaseous product. Studies to identify the catalytic mechanism of boric acid were also conducted. The spent AB solid product was found to be polyborazylene-like species, which can be efficiently regenerated using currently demonstrated methods. The results indicate that our proposed method is promising for hydrogen storage, and could be used in PEM fuel cell based vehicles.