Scientists have developed an extremely small and highly efficient catalyst that could improve the production of green hydrogen, one of the cleanest fuels being explored for the future.
The international research team, led by scientists from Tohoku University, Tokyo University of Science, Vanderbilt University and the University of Adelaide, created tiny clusters made from only 15 atoms of iridium.
Despite their microscopic size, these nanoclusters performed better than commercially available iridium catalysts and remained stable for more than 20 hours without degrading.
The findings were published in the Journal of the American Chemical Society.
Green hydrogen is produced by splitting water into hydrogen and oxygen using electricity. If the electricity comes from renewable sources such as solar or wind power, the resulting hydrogen is considered a clean fuel because it can be used without producing carbon dioxide emissions.
However, producing green hydrogen efficiently remains difficult. One of the biggest challenges is a chemical process called the Oxygen Evolution Reaction, or OER. This reaction requires a large amount of energy and takes place in a highly acidic and corrosive environment.
Very few materials can survive these harsh conditions. Iridium is one of the only metals capable of acting as an effective catalyst during the reaction. A catalyst speeds up chemical reactions without being consumed in the process. Unfortunately, iridium is extremely rare and expensive, making it difficult to use on a large scale.
For years, scientists have been searching for ways to reduce the amount of iridium needed while maintaining or even improving its performance.
The research team addressed this challenge by shrinking iridium into incredibly tiny clusters measuring only about one nanometer across.
At this scale, almost every atom is exposed on the surface, creating many active sites where chemical reactions can occur. This greatly increases efficiency while minimizing the amount of precious metal required.
Producing such tiny metal clusters has been difficult because they tend to oxidize and become unstable when exposed to air. To solve this problem, the researchers developed a surprisingly simple method that works entirely in ordinary air.
They protected the iridium atoms using two different molecules that surrounded and stabilized the clusters. This allowed them to create atomically precise clusters containing exactly 15 iridium atoms.
The researchers then attached the nanoclusters to a carbon support to create a solid catalyst. Testing showed that the new material had about 1.5 times greater mass activity than conventional commercial iridium catalysts. In other words, it generated more chemical activity while using less iridium.
The catalyst also demonstrated excellent durability, operating continuously for more than 20 hours without significant performance loss.
Further analysis showed that shrinking the iridium particles to such a tiny size altered their electronic properties in a way that made chemical reactions occur more efficiently.
The researchers believe their work could represent an important step toward more affordable and efficient green hydrogen production. Beyond hydrogen technology, the new method may also help scientists develop other high-performance metal nanoclusters for tackling global energy and environmental challenges.
As the world searches for cleaner energy solutions, these tiny clusters containing only 15 atoms could play an important role in building a more sustainable future.
