Researchers at the Massachusetts Institute of Technology (MIT) have now found a simple way to generate clean hydrogen fuel using scrap aluminum and water – when and where it’s needed.
As the world works to move away from fossil fuels and minimize their carbon emissions, many researchers are investigating whether clean hydrogen fuel can play an expanded role in various sectors.
Hydrogen fuel can be used in jet engines, for electricity generation and transportation, and even for the long-term storage of renewable energy. But while using hydrogen doesn’t generate carbon emissions, making it typically does. Today, almost all hydrogen is produced using fossil fuel-based processes, which contribute to global greenhouse gas emissions. In addition, for extensive usage, hydrogen often needs to be transported from its site of manufacture to utilization, which means its use also presents logistical challenges.
Dr. Laureen Meroueh, along with Professor Douglas Hart and Professor Thomas Eager at MIT, has proposed another option for producing hydrogen that comes from a perhaps surprising source: reacting aluminum with water. Aluminum metal will readily react with water at room temperature to form aluminum hydroxide while releasing hydrogen gas.
According to the researchers, there are two major problems that have kept aluminum from being employed as a safe, economical source for hydrogen generation. The first problem is that aluminum reacts more readily with the oxygen in the air and forms aluminum oxide. This layer of aluminum oxide naturally coats the raw metal, preventing it from coming directly into contact with water. Therefore, for the reaction to occur, one simply needs to ensure that the aluminum surface is clean and keep the oxide layer from re-forming as the reaction proceeds.
The second problem is that pure aluminum is energy-intensive to mine and produce and is not environment-friendly. Therefore, the researchers prefer scrap aluminum (which typically occurs in an alloyed form) over pure one to source the fuel. The scrap aluminum is often mixed with other elements like silicon, magnesium, or both to give additional properties like strength and corrosion resistance.
To prevent the adherence of an oxide layer on the aluminum surface, the team painted the scrap aluminum with a eutectic mixture of gallium and indium. The mixture remains in a liquid state at room temperature while being able to penetrate through the aluminum oxide and allow the release of hydrogen.
Dr. Laureen Meroueh cites several benefits to the process they used. “You don’t have to apply any energy for the gallium-indium eutectic to work its magic on aluminum and get rid of that oxide layer,” she says. “Once you’ve activated your aluminum, you can drop it in water, and it’ll generate hydrogen – no energy input required.” Interestingly, the eutectic doesn’t chemically react with aluminum. And at the end of the process, the gallium and indium can be recovered and used again – a valuable feature as gallium and (especially) indium are costly and in relatively short supply.
The research showed that aluminum could be used as a source of hydrogen, which can be stored and transported safely. “Using aluminum as our source, we can ‘store’ hydrogen at a density that’s 10 times greater than if we just store it as a compressed gas,” said Professor Douglas Hart.
This method of generating hydrogen doesn’t produce any greenhouse gas emissions, and it promises to solve the transportation problem for any location with available water, researchers noted.