Coffee, old cans, seawater — a perfect recipe for quick hydrogen production

Researchers at the Massachusetts Institute of Technology (MIT) have found a sustainable source of generating green hydrogen using aluminum recovered from soda cans and abundantly available seawater.

In a serendipitous act, they also found that the reaction could be sped up using coffee grounds, thereby improving the hydrogen production rate when required.

Hydrogen is touted as the next generation of fuels that can provide unlimited power without producing planet-warming carbon emissions.

While research is ongoing on sustainable approaches to hydrogen production, a research team at MIT is looking for ways to fuel vehicles with hydrogen without carrying the highly volatile gas around.

The MIT team has found a solution in aluminum, another abundantly available material that reacts with water to produce hydrogen and heat.

However, aluminum can do this only in its pure form. The metal also instantly reacts with oxygen in the air to form a thin oxide layer that acts as a barrier for the hydrogen production reaction.

A rare, expensive alloy as an activator

In their previous work, the research team found that treating the aluminum pellets with an alloy of rare and expensive metals, gallium and indium, works as an activator to remove the oxide layer and allow aluminum to react with water.

When the reaction was run with de-ionized water, one gram of aluminum pellets could generate 1.3 liters of hydrogen in just five minutes. However, the researchers were interested in recovering the metal alloy to be reused.

Seawater is an inexpensive and abundantly available ionic solution since it prevents the metal alloy from reacting with water, instead precipitating it outside the solution and easing its recovery.

However, seawater has a similar effect on aluminum pellets and slows down hydrogen production.

Everything but the kitchen sink

To solve the challenge of speeding up hydrogen production in seawater, the MIT researchers used various ingredients, both conventional and unconventional, in scientific research.

“We were just playing around with things in the kitchen, and found that when we added coffee grounds into seawater and dropped aluminum pellets in, the reaction was quite fast compared to just seawater,” said Aly Kombargi, a PhD student at MIT’s Department of Mechanical Engineering, and who was involved in the work.

To understand what might be accelerating the reaction, the research team approached MIT’s chemistry department, which suggested that imidazole, an active ingredient in caffeine, could be responsible.

The chemical’s molecular structure can penetrate the aluminum, but it leaves the metal alloy treatment intact so that the reaction can continue.

With all the necessary components to run a sustainable hydrogen reactor , MIT researchers plan to test the technology in marine and underwater vehicles. According to their calculations, 40 pounds of aluminum pellets could power a small underwater glider for about 30 days.

“The next part is to figure out how to use this for trucks, trains, and maybe airplanes,” added Kombargi in a press release. “Perhaps, instead of having to carry water as well, we could extract water from the ambient humidity to produce hydrogen.”

The research findings were published in Cell Reports Physical Science .