ALL Aboard

Hydrogen tops the list of promising carbon-free fuels for cars, but one of the biggest obstacles to its use is the difficulty of storing enough fuel on board to avoid frequent stops at a "hydrogen station."
How best to achieve the benchmark of 300 miles of travel without refueling? It may be to use the lightweight compound ammonia-borane to carry the hydrogen. With hydrogen accounting for almost 20 percent of its weight, this stable, non-flammable compound is one of the highest-capacity materials for storing hydrogen. In a car, the introduction of a chemical catalyst would release the hydrogen as needed, thus avoiding on-board storage of large quantities of flammable hydrogen gas. When the ammonia-borane fuel is depleted of hydrogen, it would be regenerated at a hydrogen station through a reverse reaction.
Known hydrogen-releasing catalysts are typically metals or their complexes, but they may complicate the reverse reaction. In a recent discovery, Frances Stephens and Tom Baker of Los Alamos National Lab, in collaboration with computational chemists at the University of Alabama, have shown that non-metal acids can catalyze the release of hydrogen. Their analysis has also shown that a similar mechanism of acid-initiated hydrogen release likely applies to ammonia-borane in the solid state and in ionic liquid solvents, forms that could be useful for transportation.