Yuichi Negishi and his team once stared at a vial containing just 15 iridium atoms—so small it defied conventional synthesis—and knew they were onto something transformative. These minuscule iridium nanoclusters, precisely engineered to contain exactly 15 atoms, remained stable for over 20 hours while outperforming commercial catalysts by 50% in mass activity, a breakthrough that could accelerate the clean hydrogen revolution. For years, producing green hydrogen through water electrolysis has been bottlenecked by the oxygen evolution reaction (OER), an energy-intensive process that demands rare, expensive iridium to withstand its harsh, acidic environment. With global demand for green hydrogen rising, reducing iridium use without sacrificing performance has become a critical scientific mission.
The international team—spanning Tohoku University, Tokyo University of Science, Vanderbilt University, and the University of Adelaide—cracked the code by synthesizing atomically precise Ir15 nanoclusters entirely in ambient air, a feat long considered nearly impossible due to iridium’s tendency to oxidize and degrade. Using a clever combination of polyol reduction and ligand exchange, they encapsulated the clusters with carbon monoxide and triphenylphosphine, creating a protective shield that prevented oxidation and preserved structural integrity. The resulting nanoclusters, measuring just 0.9 nanometers in diameter, were then dispersed on carbon black to form a high-performance solid catalyst.
Electrochemical tests revealed not only a 1.5-fold increase in mass activity compared to commercial iridium catalysts but also exceptional durability—no performance drop over 20 hours of continuous operation. Advanced analyses showed the clusters adopted a cationic state, enhancing their ability to adsorb reaction intermediates and enabling a more efficient Lattice Oxygen Oxidation Mechanism. This atomic-level precision maximizes catalytic efficiency while minimizing material use, a dual advantage crucial for scaling up water electrolysis systems.
Published in the Journal of the American Chemical Society, this work opens a new path toward cost-effective, high-performance catalysts. With green hydrogen poised to play a central role in decarbonizing industries from steel to shipping, every atom of iridium saved—and every efficiency gained—matters. As Negishi puts it, this discovery could mark a turning point in how we approach sustainable energy materials. The era of atom-by-atom engineering may have just begun.