An opportunity for powering marine vessels with sustainably produced hydrogen is being stirred up by MIT engineers. The recipe calls for adding aluminum-based soda cans to seawater, which results in the evolution of the gas.

As pebble-sized aluminum pellets pretreated with a gallium-indium eutectic alloy are placed in seawater, enabling the aluminum to strip out oxygen and freeing molecular hydrogen. Salt ions in the seawater can in turn attract and recover the alloy, which can be reused to generate more hydrogen in a sustainable cycle. The key to speeding up the reaction: the addition of spent coffee grounds. As reported in Cell Reports Physical Science, the presence of imidazole, a compound in caffeine, reduced the reaction time from two hours to just under five minutes and yielded 400 milliliters of hydrogen.

A small reactor to power a marine vessel or underwater vehicle with hydrogen is now under development. An onboard supply of aluminum pellets derived from recycled materials, gallium-indium and caffeine could be fed to the reactor, along with some of the surrounding seawater, to generate hydrogen on demand fuel onboard engines for motive or electrical power. Such a system is envisioned to eliminate the need to carry hydrogen fuel tanks.

A hydrogen reactor is being designed to produce hydrogen gas by mixing aluminum pellets with seawater. Source: Tony Pulsone

A system containing about 40 lb of aluminum pellets is theorized to power a small underwater glider for about 30 days by pumping in surrounding seawater and generating hydrogen to power a motor.

“We’re showing a new way to produce hydrogen fuel, without carrying hydrogen but carrying aluminum as the ‘fuel,’” said researcher Aly Kombargi. “The next part is to figure out how to use this for trucks, trains, and maybe airplanes. Perhaps, instead of having to carry water as well, we could extract water from the ambient humidity to produce hydrogen. That’s down the line.”