In the race to decarbonize, hydrogen has emerged as a promising clean fuel. But despite its potential to power industries and transport without emissions, sustainable hydrogen production faces a major hurdle – the high cost and scarcity of iridium.
Researchers at Rice University have developed a new catalyst that slashes iridium use in proton exchange membrane (PEM) electrolyzers by over 80%.
The breakthrough could make green hydrogen production far more affordable and scalable.
“This is a significant step toward making green hydrogen more accessible and scalable,” said Haotian Wang, associate professor of chemical and biomolecular engineering at Rice.
“By reducing iridium use by over 80%, we’re addressing one of the biggest economic and supply chain bottlenecks in the hydrogen economy.”
Current PEM electrolyzers rely heavily on iridium, one of the few metals that can endure the harsh acidic environment of water splitting. But iridium is among the rarest elements on Earth, costing about $160 per gram.
“Without reducing iridium consumption, the projected demand from electrolyzers alone could exceed 75% of the world’s annual supply,” Wang said. “That’s simply not sustainable if we’re serious about scaling hydrogen production.”
To solve this, the Rice team designed a catalyst where iridium atoms are embedded within a ruthenium oxide lattice instead of coating the surface.
Working with De Nora Tech, they used density functional theory and Monte Carlo simulations to predict the optimal atomic arrangement.
“Our simulations revealed that iridium atoms in the subsurface layer play a critical role,” said Thomas Senftle, associate professor of chemical and biomolecular engineering at Rice. “They help protect the ruthenium atoms above them from dissolving under extreme electrochemical conditions.”
Industrial-grade performance
The team synthesized a material named Ru₆IrOₓ, featuring a six-to-one ratio of ruthenium to iridium.
It sustained an industrial-level current density of 2 amperes per square centimeter for more than 1,500 hours with minimal degradation.
“The key is achieving a uniform distribution of iridium throughout the ruthenium oxide structure,” Senftle said. “That uniformity promotes stability because iridium helps to stabilize neighboring ruthenium atoms in the oxide lattice.”
Industrial testing by De Nora Tech confirmed the catalyst’s performance. In a 25-square-centimeter PEM electrolyzer, the Rice-designed catalyst matched the activity of pure iridium systems while using a fraction of the metal.
“Our results show that we don’t need iridium-rich catalysts to achieve durability,” Wang said. “This opens the door to mass production of cost-effective, high-performance PEM electrolyzers.”
Economic and scientific impact
An economic analysis found that replacing standard iridium oxide with Ru₆IrOₓ could cut anode catalyst costs by over 80%. The design also reduces exposure to price swings in iridium.
Beyond cost, the study offers a new paradigm in catalyst engineering, stabilizing materials from within rather than coating them for protection.
“This work highlights how theory and experiment can work hand in hand,” Senftle said. “By combining atomic-scale simulations with rigorous experimental testing, we’ve been able to pinpoint how a small amount of iridium can stabilize the entire oxide lattice.”
The research, supported by the Welch Foundation, the Packard Foundation and the National Science Foundation, could help accelerate global hydrogen adoption. “If we can make electrolyzers cheaper, more durable and less dependent on scarce materials, hydrogen can become a truly global, renewable fuel,” Wang said.
The study is published in the journal Nature Nanotechnology.
