Method to release hydrogen from ammonia borane for portable fuel cell applications

Ammonia borane (AB, NH3BH3) is considered to be a promising hydrogen storage material as it contains 19.6 wt% hydrogen. It is difficult, however, to release hydrogen from AB. Thermolysis, catalytic hydrolysis and heat generated by additional reactive mixtures are usually employed, but these methods have disadvantages that limit their use for portable applications. In this paper, we demonstrate a new approach to release hydrogen, which does not require any catalyst and produces relatively high hydrogen yield and environmentally benign byproducts. It involves nano-aluminum (nAl)/water combustion reaction, which provides heat for AB dehydrogenation and releases additional hydrogen from water. To facilitate higher H2 yield from thermolysis, as compared to hydrolysis, AB is spatially separated from the nAl/water mixture using a concentric cylindrical container. The effect of the container design on hydrogen generation is studied and optimized. This study also includes transient temperature and pressure measurements, and product characterization using mass spectrometer and 11B NMR. This approach provides H2 yield up to 9.5 wt% on material basis. Our experimental results and analysis show that a proposed power source based on this method is promising for portable electronic devices.