Discarded drinks cans could be the key to producing hydrogen fuel, researchers at the US Massachusetts Institute of Technology (MIT) have discovered, using seawater to turn scrap into sustainable energy.
The landmark findings, published in Cell Reports Physical Science journal, explain that when pure aluminium is exposed to seawater, it naturally produces bubbles of hydrogen gas – which can be used to power engines and fuel cells without releasing planet-warming emissions.
And what’s more, the reaction can be speeded up to produce hydrogen more quickly by adding a simple and widely available catalyst: caffeine.
Fresh water or seawater?
The research team, led by Aly Kombargi, a PhD student in MIT’s Department of Mechanical Engineering, pretreated aluminium with a rare-metal alloy to expose its pure state and turned it into small pellets, which were then placed into beakers of water.
Fresh water reacts with the treated aluminium fast, but using fresh water supplies is not ideal and what’s more, the expensive and rare alloy, gallium indium, used to expose the aluminium in the first place, is lost in fresh water.
Salt ions in seawater also react to the aluminium and release hydrogen, but slowly compared to fresh water. But in a satisfying circular economy of raw materials, the ions in seawater, non-existent in fresh water, can also help to recover the precious gallium indium.
Why coffee?
Trialling ways to produce the hydrogen faster with seawater then, the scientists did what anyone might do. They thought about stimulants, which led them to ask the question, if coffee can stimulate humans, what would it do to the aluminium and seawater reactions?
Sure enough, when coffee granules were sprinkled into the mix, the reaction became 24 times faster, releasing as much hydrogen gas in five minutes as previously was produced in two hours. And the gallium indium was still able to be recycled for another batch.
Applications for sea transport
Using hydrogen as a fuel comes with challenges as it is so volatile and risky to transport in a traditional tank. Instead, scientists are looking at ways to develop reactors that can be carried on-board transport. Focusing on marine or submarine vessels is a way forward, since the base ingredients for the process MIT has pioneered would be able to be carried on-board and indeed, would be freely-available all around the vessels, to produce hydrogen on-demand.
“This is very interesting for maritime applications like boats or underwater vehicles because you wouldn’t have to carry around seawater — it’s readily available,” says the study’s lead author, Aly Kombargi, a PhD student in MIT’s Department of Mechanical Engineering. “We also don’t have to carry a tank of hydrogen. Instead, we would transport aluminium as the ‘fuel,’ and just add water to produce the hydrogen that we need.”
And the process could be coming to market sooner rather than later. One member of the research team, Peter Godart, has already founded a company to turn aluminium into hydrogen fuel.
