One of the more common uses of rare transition metals is to act as catalysts. Catalysts are basically substances that speed up chemical reactions without getting used up themselves. They show up in everything from fertilizer production to the catalytic converters sitting under your car. But because these catalysts are made from rare metals like platinum and palladium, they end up being pricey. Metals like platinum are a pain to dig out, too, thanks to their rarity. So it’s no surprise that chemists have been hunting for alternatives for years. And now, we may finally have an answer in the form of aluminum, one of the most abundantly available metals on Earth.
The answer comes from King’s College London, where a team of researchers working alongside chemists from Trinity College Dublin has managed to put together a brand new form of the metal that could replace these pricier options. The metal has been engineered into a new molecule, which they call cyclotrialumane. It is basically three aluminum atoms bonded together in a triangle, making it a trimer. The full findings are published in the journal Nature Communications.
The trimer is what makes the whole thing tick, because it behaves a lot like platinum and palladium. Those two metals are great at driving chemical reactions forward, but, according to senior author Dr. Clare Bakewell, platinum and palladium are a whopping 20,000 times pricier than aluminum. But cyclotrialumane is more than just a budget knockoff, since it can pull off reactions even pricier metals struggle with. It also holds together when dissolved in different solutions. That’s a big deal because many lab-grown reactive molecules end up breaking down the second they touch a solvent. These advantages lead to a number of wins for everyone.
What this fancy aluminum can actually do
The molecule has shown early promise in the lab, suggesting it could eventually help drive important chemical reactions. The researchers were able to use it to split dihydrogen, the H2 molecules that make up hydrogen gas. Splitting the hydrogen molecule is the main driver of hydrogen energy production, and the same process that runs hydrogen-powered vehicles, so this could help with clean fuel production. The molecule also acted as a catalyst in the controlled chain growth of ethene, which happens to be one of the main building blocks of plastics.
Then there is the weird stuff. Bakewell and her team found that reacting the trimer with ethene creates ring structures that nobody has documented before. These include rings built out of five and seven atoms of aluminum and carbon mixed together. That hints at a whole new class of reactions that go past what platinum and palladium can manage on their own.
Today, most of the world’s platinum gets dug up in South Africa. Extracting even just a few grams of it takes processing at least a ton of ore, which needs a ton of energy. That’s a problem since the energy grid there still relies heavily on coal. Swapping platinum for aluminum would cut down on the environmental impact while also reducing cost. The metal is already proving its worth in other green initiatives, as researchers have found a new way to recycle batteries using old aluminum foil. Of course, the team is still in the exploratory phase, and a lot of work is still needed to pull off the above wins at scale. But if the results hold up, aluminum may end up a whole lot overqualified to simply sit in your kitchen drawer as foil.
https://www.slashgear.com/2160319/new-form-aluminum-precious-metals-replacement/