Ammonia Borane Based Nanocomposites as Solid-State Hydrogen Stores for Portable Power Applications

Ammonia borane (AB) based nanocomposites are studied with the aim of developing a promising solid-state hydrogen store that complies with the requirements of a modular polymer electrolyte membrane fuel cell (PEM FC) in a portable power pack system. AB-carbon nanocomposites (prepared via ball milling or solution-impregnation) demonstrate improved hydrogen release performance compared to AB itself in terms of onset temperature and hydrogen purity, while maintaining a gravimetric density of more than 5 wt.% H-2. The most promising of these materials is an AB-AC (activated carbon) composite, synthesized via solution impregnation with an optimal dehydrogenation temperature of 96 degrees C. When combined with an external nickel chloride filter downstream, no evolved gaseous by-products can be detected above 100 ppb. The feasibility of an AB-AC storage tank is further investigated using simulations in which the reaction rate and the hydrogen flux is found to be nearly constant as the temperature front propagated from the bottom to the top of the tank after initiation.