In a groundbreaking advancement that merges materials science and energy technology, an international team of scientists from South Korea and Japan has unveiled a novel crystal capable of “breathing” oxygen. This exceptional property, marked by the crystal’s ability to reversibly release and absorb oxygen at relatively low temperatures, opens promising avenues in the development of next-generation clean energy devices, novel electronic components, and adaptive thermal technologies. Unlike previous materials that demand harsh conditions or degrade swiftly, this newly synthesized crystal maintains structural stability through repeated oxygen cycling, signaling a paradigm shift in smart material design.
At the heart of this breakthrough lies a carefully engineered metal oxide compound composed of strontium, iron, and cobalt, denoted as SrFe₀.₅Co₀.₅O₂.₅. The material’s architecture permits selective reduction and oxidation processes wherein cobalt ions undergo a reversible valence change, making it uniquely capable of oxygen uptake and release without compromising its crystal lattice. This sophisticated mechanism enables the crystal to mimic respiratory behavior—akin to inhaling and exhaling oxygen molecules on command. Such dynamic oxygen modulation is pivotal for solid oxide fuel cells and other energy systems, where controlled oxygen ion transport governs device efficiency and durability.
Professor Hyoungjeen Jeen of Pusan National University spearheaded the research initiative, bringing together a multidisciplinary team to dissect the fundamental chemistry and physics underpinning this material’s operation. Collaborating with Professor Hiromichi Ohta of Hokkaido University, the researchers employed advanced epitaxial growth techniques to fabricate the crystal with high precision, ensuring epitaxial quality crucial for elucidating the complex reductive and oxidative phenomena. Their findings, published in the esteemed journal Nature Communications (August 15, 2025), underscore a rare balance between chemical reactivity and structural resilience seldom observed in metal oxides.
This strontium-iron-cobalt oxide crystal leverages cobalt’s unique electronic configuration, which facilitates the selective reduction process. Unlike conventional oxygen storage materials that indiscriminately accommodate changes in metal oxidation states—often destabilizing the crystalline framework—this compound retains its periodic lattice by limiting redox activity to cobalt ions alone. This selectivity engenders a novel, stable phase post-reduction, heretofore unseen in similar perovskite-related oxides. The new crystal phase demonstrates robust reversibility, recovering its initial structure upon oxygen reinsertion, thereby validating its practical viability for cycling applications.
Oxygen mobility and exchange underpin many ecosphere technologies, from energy generation to environmental control. Solid oxide fuel cells (SOFCs), for instance, rely heavily on oxygen ion transport within ceramic layers to efficiently convert hydrogen fuel into electrical energy. The capacity of SrFe₀.₅Co₀.₅O₂.₅ to modulate oxygen content at moderate temperatures enhances fuel cell operation by reducing thermal strain and prolonging operational longevity. Moreover, the oxygen-breathing ability aligns closely with emerging concepts in thermal transistors—devices that modulate heat flow with unprecedented precision, analogous to electronic transistors controlling current.
Beyond energy, the smart material’s dynamic oxygen handling can revolutionize adaptive architecture and electronics. Smart windows that can adjust their thermal transmittance based on oxygen-induced phase transitions will optimize building energy consumption, reducing reliance on air conditioning and heating. Similarly, electronic components fabricated with these materials promise breakthroughs in stability and functionality by leveraging in-situ tunable oxygen stoichiometry. The reversible oxygen exchange presents a versatile platform for designing devices that respond in real time to environmental or operational stimuli.
Previous materials exhibiting oxygen storage or diffusion characteristics often suffered from structural degradation or required excessively high temperatures—sometimes exceeding 700°C—to activate oxygen exchange. These limitations hindered their scalability and practical application. In contrast, the newly reported SrFe₀.₅Co₀.₅O₂.₅ crystal operates robustly at considerably lower temperatures, maintaining its phase integrity even after numerous oxygen insertion and extraction cycles. This thermal threshold significantly streamlines the integration of these materials into existing technologies, facilitating reduced energy input and improved safety.
The research team employed state-of-the-art characterization techniques, including synchrotron X-ray diffraction and electron microscopy, to resolve the subtle phase transitions triggered by oxygen mobility. Their meticulous analysis showed that only cobalt ions undergo reduction from Co³⁺ to Co²⁺ during oxygen release, while iron and strontium ions remain chemically inert within the lattice. This selective reduction is critical for maintaining the host framework’s rigidity. Such insights not only elucidate the fundamental redox chemistry at play but also pave the way for targeted engineering of similar materials with customized oxygen exchange profiles.
Reversibility—a hallmark of any sustainable oxygen storage or operating system—is impressively demonstrated in this crystal. By cycling the material through controlled oxygen atmospheres, the researchers showed that it consistently regains its initial crystalline structure and oxygen content without performance degradation. This cycling endurance, unprecedented for materials operating at modest temperatures, heralds a new category of “oxygen lung” materials that could underpin autonomous and energy-efficient devices capable of adaptive self-regulation.
This development resonates broadly with the global push towards cleaner, smarter technologies. By controlling oxygen with precision and stability, devices based on this material could drastically reduce greenhouse gas emissions inherent in traditional energy harvesting methods. Additionally, its ability to accommodate reversible oxygen flux may inspire innovations in sensors, catalysis, and energy storage systems. The interdisciplinary nature of this discovery—intersecting physics, chemistry, and engineering—underscores the vitality of collaborative research for addressing complex global challenges.
Looking ahead, opportunities abound for tailoring this material’s properties via chemical doping, strain engineering, and nanoscale patterning to further optimize oxygen kinetics and thermal stability. Integrating such materials into prototype devices will test their efficacy beyond laboratory conditions and catalyze their translation from experimental novelty to commercial reality. The convergence of innovative crystal chemistry and device engineering promises to unlock new functionalities unattainable with conventional materials.
In summary, the SrFe₀.₅Co₀.₅O₂.₅ crystal embodies a pioneering step forward in the development of smart materials capable of reversible oxygen management under mild conditions. This advancement not only enriches the fundamental understanding of solid-state redox chemistry but also lays foundational groundwork for transformative applications in clean energy, electronics, and environmentally responsive infrastructure. As the world intensifies its energy transition efforts, materials with innate adaptability like this oxygen-breathing crystal will be indispensable allies in crafting sustainable technological landscapes.
Subject of Research:
Development of a reversible oxygen-breathing crystal material with potential applications in clean energy, electronics, and thermal management.
Article Title:
Selective reduction in epitaxial SrFe0.5Co0.5O2.5 and its reversibility.
News Publication Date:
15-Aug-2025
Web References:
https://doi.org/10.1038/s41467-025-62612-1
References:
Joonhyuk Lee, Hyoungjeen Jeen, et al. “Selective reduction in epitaxial SrFe0.5Co0.5O2.5 and its reversibility,” Nature Communications, August 15, 2025.
Image Credits:
Prof. Hyoungjeen Jeen, Pusan National University, Korea.
Keywords
Materials science, Crystallography, Chemistry, Physics, Nanotechnology, Engineering, Energy, Electrical engineering, Electrochemistry, Electronics
