As the global demand for efficient and low-carbon energy technologies continues to grow, protonic ceramic fuel cells (PCFCs) have attracted increasing attention because of their high energy conversion efficiency, fuel flexibility, and relatively low operating temperatures compared with conventional solid oxide fuel cells. Operating at intermediate temperatures (400–700 °C), PCFCs can reduce material degradation and system costs while maintaining efficient electrochemical performance. However, their practical application is still limited by the slow oxygen reduction reaction (ORR) at the cathode, as well as insufficient long-term stability under humid and CO2-containing operating conditions. Developing cathode materials that simultaneously exhibit high catalytic activity, fast charge transport, and good environmental stability therefore remains an important research challenge.
To address these issues, the research team developed a self-assembled triple-conducting cathode based on a synergistic Zn/Yb co-doping strategy combined with temperature-induced nanoparticle exsolution. The material was synthesized using a conventional sol-gel method, followed by calcination under carefully controlled thermal conditions. During heat treatment at 950 °C, hexagonal BaCoO3-δ nanoparticles were spontaneously exsolved from the cubic perovskite matrix, forming a stable dual-phase structure without the need for additional surface modification or infiltration processes.
This team published their work in Journal of Advanced Ceramics on June 22, 2026.
The material design combines two complementary mechanisms. Zn/Yb co-doping modifies the local charge distribution within the perovskite lattice, increases the concentration of oxygen vacancies, lowers the oxygen vacancy formation energy, and promotes both oxygen-ion and proton transport. Meanwhile, the in-situ exsolved nanoparticles increase the density of catalytic active sites and improve interfacial charge transfer, leading to enhanced oxygen reduction kinetics. Compared with conventional infiltration-based approaches, the temperature-induced exsolution strategy simplifies the fabrication process while providing stronger particle–matrix interactions that help maintain structural stability.
To understand the origin of the improved electrochemical performance, the researchers combined extensive experimental characterization with first-principles calculations. Structural evolution was investigated using X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy, oxygen temperature-programmed desorption, thermogravimetric analysis, and electrical conductivity relaxation measurements were employed to evaluate oxygen vacancy concentration, oxygen transport, and hydration behavior. Density functional theory calculations further revealed that Zn/Yb co-doping redistributes electronic charge, weakens metal–oxygen bonding, enhances d–p orbital hybridization, and facilitates oxygen vacancy formation, providing theoretical support for the experimentally observed improvements in ionic and electronic transport.
The performance of the new cathode was systematically evaluated through comparison with conventional cathode materials under identical testing conditions. A single cell using the optimized cathode achieved a peak power density of 0.99 W cm-2 at 600 °C and 1.22 W cm-2 at 650 °C, outperforming the reference BCFZY cathode throughout the investigated temperature range. Electrochemical impedance spectroscopy showed lower polarization resistance under both dry and humid atmospheres, indicating faster oxygen reduction kinetics. Under humidified conditions, the cathode maintained excellent electrochemical activity even as the water content increased to 20%, demonstrating strong hydration-related transport capability.
Long-term stability was also evaluated through multiple testing methods. Symmetric cells exhibited stable area-specific resistance during continuous operation for 180 hours in humidified air, while single cells operated continuously for more than 100 hours at 600 °C with a degradation rate of only 0.091% h-1. Additional CO2 tolerance experiments and post-test structural characterization confirmed that the dual-phase cathode maintained its structural integrity and electrochemical performance under both humid and CO2-containing environments, indicating good compatibility with practical operating conditions.
Professor Guo Youmin, the project leader, said, "Our objective was to develop a cathode design strategy that improves activity, conductivity, and stability simultaneously while maintaining a simple and scalable synthesis process. The combination of cation-driven charge modulation and temperature-induced exsolution provides a practical approach for designing high-performance PCFC cathodes and offers new insights into the relationship between lattice chemistry, oxygen vacancies, and electrochemical performance."
The proposed strategy provides an effective approach for optimizing cathode materials through the combined regulation of crystal chemistry and microstructure. Although additional studies under practical operating conditions are still needed, the present work demonstrates the potential of self-assembled dual-phase cathodes for improving the efficiency and durability of intermediate-temperature protonic ceramic fuel cells, and may also provide useful guidance for the development of other electrochemical energy conversion devices.
About Authors
Youmin Guo is a Professor and Ph.D. supervisor at the School of Materials Science and Engineering, Anhui University. Her research focuses on solid oxide fuel cells, membrane reactors, electrochemical catalytic conversion, gas sensors, and functional materials.
Zuoqing Liu is a Postdoctoral Research Fellow at the School of Materials Science and Engineering, Anhui University. His research interests include protonic ceramic fuel cells, solid oxide electrochemical cells, membrane reactors, and high-temperature electrolysis.
Funding
This work was supported by the National Key R&D Program of China (Grant Nos. 2021YFA1501900, 2024YFE0101500, and 2026YFE0151900), the China Postdoctoral Science Foundation (Nos. S202418001/198 and 2025M780002), and the Scientific Research Foundation of Education Department of Anhui Province (No. 2025AHGXZK40238). The authors also acknowledge the support from Prof. Yu Liu, which is associated with the National Natural Science Foundation of China (No. 52202324) and the independently funded research project (No. E3550101) of the Nanjing Future Energy System Research Institute, Chinese Academy of Sciences (CAS).
DOI: 10.26599/JAC.2026.9221340
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC's 2025 IF is 14, ranking in Top 1 (1/34, Q1) among all journals in "Materials Science, Ceramics" category, and its 2025 CiteScore is 24.6 (6/133) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
