| Dec 23, 2025 |
Researchers discover that embedding iridium atoms inside catalyst crystals instead of on the surface dramatically improves durability for green hydrogen production.
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(Nanowerk News) Producing green hydrogen through water electrolysis requires catalysts that can survive punishing acidic conditions while driving the oxygen evolution reaction. But the harsh environment attacks most affordable catalyst materials, causing metals to dissolve, crystal structures to warp, and oxygen atoms to migrate out of position. These degradation processes have limited the practical lifespan of promising non-precious metal catalysts like cobalt oxide spinels.
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Scientists have tried adding small amounts of precious metals to stabilize these catalysts, but not all approaches work equally well. Until now, researchers lacked a clear understanding of why some single-atom configurations protect the underlying material while others fail.
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A research team from the University of Science and Technology of China and partner institutions has now cracked this puzzle. Their study, published in eScience (“Site-specific stabilizing effect of single atoms on spinel oxides for acidic oxygen evolution”), reveals that the precise location where a single iridium atom sits within a cobalt oxide catalyst determines whether the material thrives or falls apart under acidic oxygen evolution conditions.
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| Site-specific stabilizing effect of single atoms on spinel oxides for acidic oxygen evolution. (Image: Reproduced from DOI:10.1016/j.esci.2025.100402, CC BY)
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Two Positions, Vastly Different Outcomes
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The team engineered two distinct catalyst configurations: one with iridium atoms anchored at surface hollow sites and another with iridium atoms embedded directly into the crystal lattice. Using a battery of structural analysis techniques including transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy, they confirmed that each configuration creates a fundamentally different electronic environment. Lattice-embedded iridium expands the crystal structure slightly and forms stronger bonds with surrounding oxygen atoms.
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Dramatic Durability Differences
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Electrochemical testing revealed stark contrasts in performance. After 1000 cycles in perchloric acid solution, plain cobalt oxide lost 40.4% of its cobalt to dissolution. Surface-anchored iridium reduced this loss to 28.4%. But lattice-embedded iridium slashed dissolution to just 2.8% while maintaining nearly unchanged current output.
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Long-term stability tests proved even more impressive. The lattice-embedded catalyst ran for 200 hours at standard current density and survived 60 hours at industrial-scale current density in a proton exchange membrane water electrolyzer, matching the performance of leading acidic oxygen evolution catalysts.
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Atomic-Level Protection Mechanism
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Real-time spectroscopy experiments showed that only the lattice-embedded iridium maintained the catalyst’s cobalt-oxygen and cobalt-cobalt structural bonds under operating voltages. Computer simulations using density functional theory explained why: embedding iridium in the lattice dramatically raises the energy barriers that cobalt and oxygen atoms must overcome to migrate out of their positions. The calculations showed migration barriers of 3.31 electron volts for cobalt and 3.26 electron volts for oxygen, along with increased energy costs for forming oxygen vacancies. The enhanced bonding between cobalt, iridium, and oxygen atoms throughout the structure provides additional reinforcement.
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“The precise position of a single atom can completely transform catalyst durability,” the study’s co-author explained. “By embedding iridium directly into the lattice, we substantially strengthened the metal-oxygen network and suppressed both cobalt and oxygen migration—the primary causes of acidic OER degradation. This atom-level strategy demonstrates that stability can be engineered with precision, enabling high performance with far lower noble-metal usage. It provides a clear and rational pathway for designing the next generation of robust acidic OER catalysts.”
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Implications for Green Hydrogen
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This discovery establishes a design framework for building highly stable catalysts while minimizing precious metal content. The impressive durability demonstrated in real electrolyzer testing suggests strong potential for industrial hydrogen production systems that must operate reliably for years under corrosive conditions.
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The site-specific stabilization strategy should extend beyond cobalt oxide to other catalyst families including spinels, perovskites, and mixed-metal oxides. By tailoring where single atoms sit within these structures, researchers can engineer specific bonding characteristics and migration resistance.
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By pinpointing the atomic-level features that control long-term stability, this work advances the field toward practical, affordable electrolyzers capable of producing green hydrogen at the scale needed to decarbonize energy systems.
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