3 min readHere’s what you’ll learn when you read this story:
- The precious metals known as platinum group metals (PGMs) are vital as catalysts in chemical reactions, but they’re difficult and environmentally damaging to source.
- A new study aims to create an aluminum-based alternative by arranging aluminum atoms in a trimeric (a.k.a. triangular) structure.
- Preliminary results show that this new kind of aluminum enables reactions such as splitting dihydrogen and creating ethene, and could outperform transition metals with unprecedented levels of reactivity.
On December 6, 1884, an 8.9-inch, 100-ounce pyramid of near-solid aluminum was placed atop the Washington Monument, signifying the completion of the 40-year-long project. Although a strange choice of material by today’s standards—after all, you can buy reams of the stuff in supermarkets for just a few dollars—back then, refined aluminum cost nearly as much as silver, making it quite a luxurious choice. The drastic price reduction from $550 per pound in 1852 (roughly $23,000 in today’s terms) to less than $1 per pound at the start of the 20th century revolutionized the modern economy.
Fast-forward to the 21st century, and aluminum is once again poised to become the much-needed cheap alternative for an immensely important technology—catalysts. In a new paper published in the journal Nature Communications, a team of scientists from King’s College London and Trinity College Dublin describe a new kind of aluminum called “cyclotrialumane,” which features a three-aluminum-atom compound arranged in a trimeric (a.k.a. triangular) structure. With its strong reactivity and ability to hold up when dissolved in different solutions, this new aluminum could be a cheaper and more environmentally friendly alternative to typical catalysts, which usually hail from the platinum group metals (PGMs, a special subset of transition metals) of the periodic table.
“Transition metals are the workhorses of chemical synthesis and catalysis, but many of the most useful are becoming increasingly difficult to access and extract,” Clare Bakewell, the senior author of the study from King’s College London, said in a press statement. “Chemists have been looking towards more common elements from the periodic table, and we chose [aluminum], as it’s super abundant, making it ~20,000 times less expensive than precious metals such as platinum and palladium.”
Platinum and palladium are such attractive catalyst candidates because they’re highly resistant to corrosion and oxidation, yet they easily break and form chemical bonds due to their advantageous electronic signatures. That’s pretty helpful if you’re a chemist, but getting your hands on PMGs isn’t easy, and it’s environmentally costly. Most of the world’s platinum, for example, comes from South Africa, which continues to use coal for a majority of its electricity needs, and to extract only a few grams of PGMs requires the energy-intensive processing of at least one ton of ore. In other words, a cheaper, more sustainable, and widely-available alternative would be a complete game-changer.
The cyclotrialumane that Bakewell and her team created is an exceptionally good catalyst for a number of reactions, perhaps most importantly for the splitting of dihydrogen—an important chemical process in the production of hydrogen energy—and creating ethene, which is used in plastics.
However, by exploring the catalytic properties of these new types of aluminum, the researchers also discovered novel reactions that exceed the capabilities of transition metals.
“We can use this aluminum trimer to build completely new compounds with levels of reactivity that have never been observed before,” Bakewell said in a press statement. “These capabilities go beyond the transition metals we were originally trying to mimic, to the forefront of chemical research.”
Maybe that hunk of aluminum perched atop the Washington Monument deserves its hallowed place after all.
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Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.