seawater caffine fuel innovation

Innovative zero-emissions fuel sources

MIT engineers have unveiled a sustainable energy solution using recycled soda cans and seawater. When pure aluminum reacts with seawater, it generates hydrogen gas, a zero-emission fuel. Adding caffeine significantly enhances this reaction.

In Cell Reports Physical Science, researchers present a method to produce hydrogen gas by introducing pretreated aluminum pellets into filtered seawater. The aluminum, treated with a rare-metalalloy, reacts with seawater, while salt ions help recover the alloy for reuse, creating a sustainable hydrogen generation cycle.

The researchers observed that the reaction between aluminum and seawater produced hydrogen gas at a slow rate. However, upon adding coffee grounds experimentally, they discovered a notable acceleration in the reaction.

The study revealed that even a small dose of imidazole, found in caffeine, could significantly hasten the reaction, achieving the same hydrogen production in five minutes rather than two hours.

Applications and Future Developments

Small-Scale Reactor for Marine use

Researchers are creating a small-scale reactor intended for deployment on marine vessels or submersibles. This system would contain aluminum pellets sourced from recycled soda cans and aluminum products, along with gallium-indium and caffeine. These materials could be periodically introduced into the reactor with seawater to generate hydrogen on demand, which would then power an onboard engine or produce electricity to run the vessel.

"This technology is especially promising for maritime uses, including boats and underwater vehicles, as it leverages the abundance of seawater, removing the necessity to transport it," states Aly Kombargi, lead author and Ph.D. candidate in MIT's Mechanical Engineering department.

"There is no need to transport a hydrogen tank; instead, aluminum is used as the 'fuel,' and hydrogen is produced when water is added."

The co-authors of this study include Enoch Ellis, a chemical engineering undergraduate; Peter Godart, Ph.D. '21, who founded a company focused on aluminum recycling for hydrogen fuel; and Douglas Hart, MIT professor of mechanical engineering.

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MIT engineers are enhancing a straight forward chemical reaction where pebble-sized aluminum pellets, immersed in filtered seawater, rapidly generate hydrogen gas. This efficient and sustainable method could power engines or fuel cells on marine and underwater vehicles.

Deploy Shields

The MIT team, under Hart's leadership, is pioneering efficient, eco-friendly methods for hydrogen production, aiming to power engines and fuel cells with zero carbon emissions.

Hydrogen vehicles often face the issue of onboard storage, similar to gasoline tanks, which can be hazardous due to hydrogen's explosive nature. Hart's team is investigating ways to utilize hydrogen fuel without the continuous transport of the gas.

The team identified aluminum as a viable alternative--an abundant and stable material that, when exposed to water, initiates a simple chemical reaction producing both hydrogen and heat.

The reaction is hindered by a catch-22: Aluminum must be in its pure, unoxidized form to generate hydrogen when it interacts with water. Exposure to air creates a protective oxide layer that halts the reaction, which is why hydrogen does not immediately bubble from a soda can in water.

In prior research, the team discovered that using fresh water allowed them to overcome aluminum's oxide barrier. By pretreating aluminum with a rare metal alloy containing specific amounts of gallium and indium, they maintained the reaction with water. This alloy acts as an "activator," removing oxide buildup and exposing a reactive pure aluminum surface.

In experiments with de-ionized water, a single pretreated aluminum pellet was found to generate 400 milliliters of hydrogen in just five minutes. It is estimated that 1 gram of these pellets could produce 1.3 liters of hydrogen within the same time frame.

For large-scale deployment, the system would need a large supply of gallium-indium, which is both pricey and not abundant.

"To ensure cost-effectiveness and sustainability, recovering the alloy after the reaction was essential," notes Kombargi.

By The Sea

The team's recent study reveals a technique for reclaiming and reusing gallium indium by employing an ionic solution. These electrically charged ions prevent the alloy's reaction with water, allowing it to be precipitated and collected for reuse.

"Seawater, being a plentiful and economical ionic solution, was ideal for the experiments," states Kombargi, who tested the approach using seawater from Revere Beach. "We collected the water, filtered out sand and algae, and found that aluminum produced consistent results."

He observed that adding aluminum to filtered seawater did produce hydrogen, and he was able to recover the gallium-indium alloy afterward. However, the reaction was notably slower than in fresh water. The ions in seawater shield the gallium-indium, allowing for its recovery, but also from a barrier on the aluminum that impedes the reaction with water.

The researchers sought to expedite the reaction in seawater by testing an assortment of innovative and non-standard compounds.

"During informal experiments, we discovered that incorporating coffee grounds into seawater significantly accelerated the reaction rate when aluminum pellets were introduced," Kombargi notes.

To investigate the cause of the accelerated reaction, the team consulted with MIT's chemistry department. They recommended experimenting with imidazole, a componenet of caffeine, known for its ability to penetrate aluminum and maintain the integrity of gallium indium's ionic shield.

"That was a major breakthrough for us," Kombargi notes. "We achieved our goals: efficient recovery of gallium indium and a rapid, effective reaction."

The researchers are confident they possess the key componenets for a sustainable hydrogen reactor. Initial tests will focus on marine and underwater vehicles. They estimate that a reactor with 40 pounds of aluminum pellets could fuel a small underwater glider for approximately 30 days by using seawater to produce hydrogen for propulsion.

"We're presenting an innovative method for hydrogen fuel production that involves transporting aluminum instead of hydrogen itself," Kombargi explains. "Our next goal is to explore applications for trucks, trains, and potentially airplanes. Future developments may involve extracting water from ambient humidity to generate hydrogen, eliminating the need to transport water."

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