Mapping catalyst failure to advance clean hydrogen fuel production
A new study co-led by computational Penn engineering professor Aleksandra Vojvodic and collaborators offers an unprecedented view of the complicated degradation process of a material based on one of the rarest elements, iridium. Their findings, which show how this catalytic agent breaks down at the atomic scale, pave the way for better hydrogen fuel production.
3 min. read
Key Takeaways
Hydrogen is a promising, versatile clean fuel source, but current production converting it from water is costly and energy-intensive due to its reliance on rare catalysts like iridium oxide (IrO2).
As IrO2 degrades during the process of water splitting, improving its durability is essential for scaling hydrogen fuel technologies.
A collaborative research team, including Penn’s Aleksandra Vojvodic, computationally identified the IrO2 nanoparticle structures at an atomic scale that better resist degradation under real operating conditions.
This work could enable longer-lasting catalysts, using less iridum, improving renewable hydrogen fuel production.
Hydrogen is the most abundant element in the universe. When it meets with oxygen in combustive reactions, massive amounts of energy can be generated, and water, as steam or liquid, is the only byproduct. This makes hydrogen an appealing alternative to fossil fuels for powering everything from vehicles to power plants.
A promising way to produce hydrogen is electrolysis—splitting water using electricity—but this approach is both expensive and energy-intensive and relies on rare materials such as iridium oxide (IrO2) to act as a catalyst to speed up reactions.
But IrO2 is among the rarest non-radioactive elements in the Earth’s crust. And not unlike how metals rust over time,iridium oxide catalysts slowly degrade during these reactions, as the harsh acidic and high-voltage conditions required “eat away at” the surface of IrO2 crystals.
This is why understanding exactly how iridium oxidedegrades is a crucial step toward designing more durable materials that require significantly less of this precious metal while helping to reduce carbon emissions in the energy and chemical industries worldwide.
Now, a new study co-led by Aleksandra Vojvodic of the University of Pennsylvania and collaborators at Duke University offers an unprecedented view of that degradation process, capturing how IrO2 nanocrystals dissolve and change shape during electrolysis. The findings, published in the Journal of the American Chemical Society, provide critical insight into why today’s best catalysts still fail and how future materials might last longer.
“Historically, scientists often treated the binding sites of catalysts as perfect static surfaces that just sit there while a reaction happens on top of them,” says Vojvodic, the Rosenbluth Professor at the Department of Chemical and Biomolecular Engineering at Penn Engineering. But the team’s combined computational modeling and physical imaging prove there’s far more to the story; the iridium oxide actively changes its shape, transforming under differing conditions before completely decomposing.
By modeling the process and watching it unfold frame-by-frame, the research team discovered that these materials don’t dissolve evenly. Instead, initially flat, smooth surfaces become defective and jagged, and as they transform into more complex surfaces, they cause more irregular nanoparticle shapes.
Intriguingly, they found that the sides of a single nanoparticle dissolved in completely different ways at the same time because each has a unique arrangement of atoms and distinct chemical properties. As a result, some sides slowly lost small clusters of atoms, while other sides saw entire layers of atoms peel away all at once.
A morph of an iridium oxide nanoparticle with the computational atomic scale model with different reaction processes on the left and the experimentally observed atomic level resolved nanoparticle on the right.
(Image: Courtesy of Rachel Thatcher and Joseph Nicolas)
“The results were incredible,” says co-senior author Ivan A. Moreno-Hernandez of Duke. “It’s kind of like a block tower game—you remove one little piece, and it all falls apart. It was very unexpected.”
To understand why certain surfaces crumbled so drastically while others held firm, Vojvodic’s team used intensive quantum mechanical modeling to map the stability of smooth, well-ordered surfaces versus those with flaws or kinks, revealing how the electrical voltages used to split water force the atoms in the particles to naturally reorganize and dissolve. They found that, under operating conditions, the most energetically stable surfaces are actually the rougher ones with more atomic steps and edges—exactly the kinds of structures that emerged during the microscopy experiments as the particles degraded.
“Our simulations acted like an ultra-high-resolution lens, allowing us to see the very first, invisible moments of decay and understand exactly how the electrical voltage forces certain surfaces to become vulnerable,” Vojvodic says.
The team confirmed these results by examining the catalysts recovered from a water electrolyzer. They found that they perfectly matched what they saw under the microscope: once-smooth crystal surfaces had become rough and uneven. And as this degradation occurred, the machine needed more electricity to keep running, directly linking tiny structural damage in the material to declining performance in a real clean-energy device.
Vojvodic’s team is now using the extensive dataset generated by the project to train machine learning models of complex nanoparticles, creating a new data-driven approach to catalyst design. Because the dataset captures behavior across larger systems and a broader range of conditions than traditional simulations alone, it could help accelerate the search for longer-lasting materials. The team has already identified one side of the crystal as especially resistant to dissolving, a finding that could guide the design of future catalysts for electrolyzers that are more durable, more efficient, and less dependent on scarce iridium.
“We finally have something approaching an atomic-level blueprint of how these materials fail under real operating conditions,” says Vojvodic. “The next step is to use this predictive power to design the next generation of electrocatalysts from the bottom up—materials that require a fraction of the precious iridium but can endure the harsh realities of commercial clean-energy technologies.”
Aleksandra Vojvodic is a professor in the Department of Chemical and Biomolecular Engineering at the School of Engineering and Applied Science and director of the Penn Institute for Computational Science at the University of Pennsylvania.
Ivan A. Moreno-Hernandez is an assistant professor of Chemistry at Duke University.
Other authors include Ph.D. students Rachel Thatcher, Joseph Nicolas, and Daniel Intriago, as well as undergraduate students Max C. Huang, and Achala I. Kankanamge of the University of Pennsylvania; and students S. Avery Vigil, Ziqing Lin, and Matteo Fratarcangeli of Duke University.
This work received support from the National Science Foundation (Awards CHE-2441703, DGE-2139754, and ECCS-2025064), the Department of Energy (Award DE-SC0025263 and Contract DE-AC02-05CH11231), the National Energy Research Scientific Computing Center (Awards ERCAP0023161, ERCAP0033461, and BES-ERCAP0030785), the Vagelos Institute for Energy Science, and Technology at the University of Pennsylvania, and the State of North Carolina.
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