Reversible protonic ceramic electrochemical cells (R-PCECs) are considered as the highly promising contraptions for bidirectional electric energy generation or storage, capable of efficiently converting electrical and chemical energy in mutual directions. Compared with the traditional solid oxide cells (SOCs), the operating temperature is relatively low, which is conducive to reducing production costs and service life. However, it has higher requirements for the oxygen electrode material.
Firstly, the oxygen electrode should exhibit substantial catalytic performance for both the oxygen reduction/evolution reaction (ORR&OER) within low temperature range. Secondly, the oxygen electrode must be sufficiently tolerant to steam because water is generated in or fed to the oxygen electrode when the R-PCEC is operated in the fuel cell (FC) or water electrolysis (EC) mode. Thirdly, the oxygen electrode is always under polarization when the cell is working, which may lead to element segregation.
Recently, a team of SOCs led by Shaorong Wang from China University of Mining and Technology, China first reported that the degradation mechanism of the BFCZY oxygen electrode at 550-650 °C under 0-50 vol% steam with/without polarization. A straightforward solution infiltration technique was used to create BCO-BFCZY heterointerfaces in the oxygen electrode. The BCO-BFCZY oxygen electrode exhibited significantly enhanced activity and durability for ORR and OER, resulting in high performance and durability of the R-PCECs. Furthermore, the ORR/OER kinetics as well as the durability of the BCO-BFCZY oxygen electrode were examined through density functional theory (DFT) research.
The team published their work in Journal of Advanced Ceramics on May 29, 2025.
"In this report, we have revealed the degradation mechanism of the BFCZY oxygen electrode under humid air. The degradation can be ascribed to the formation of BCO due to the water-promoted segregation of elemental Ba, which could affect the oxygen surface exchange of BFCZY. The degradation is more severe at lower temperatures, in higher steam concentrations, and in the fuel cell mode. Both the activity and stability of the BFCZY oxygen electrode can be remarkably improved through the constructing of BCO-BFCZY heterointerfaces by BCO coating. Meanwhile, DFT calculations also confirmed the high ORR&OER activity, and the high stability of the BCO-BFCZY electrode. Furthermore, the R-PCECs with the BCO-BFCZY oxygen electrode proved enhanced performance and stability in both the FC and EC modes. This study established a foundation for the stability research of oxygen electrodes and proposed a promising technology to improve the electrochemical performance and durability of oxygen electrodes for R-PCECs." said Shaorong Wang, professor at School of Chemical Engineering & Technology at China University of Mining and Technology, a senior expert whose research interests focus on the field of solid oxide cells.
"Perovskite-structured BaFe0.4Co0.4Zr0.1Y0.1O3-δ (BFCZY) exhibits proton-electron-oxygen ion triple conductions and high catalytic activity of ORR and OER at low temperatures, but its stability in high-humidity air remains to be verified," said Shaorong Wang.
With the increase of steam concentration and the decrease of temperature, the degradation of the BFCZY oxygen electrode becomes more severe. Furthermore, the degradation rate of Rp of the BFCZY electrode under the cathodic polarization (0.798 Ω cm2/100 h) is greater than that under the anodic polarization (0.419 Ω cm2/100 h). At 600 °C in 30 vol% H2O-air, the heterointerface engineering with BCO-BFCZY decreases the polarization resistance of the electrode by half (from 0.42 to 0.21 Ω cm2) and the decay rate by more than one order of magnitude (from 0.384 to 0.026 Ω cm2/100 h). DFT calculations show that the heterogeneous interface reduces the formation energy of oxygen vacancies and the adsorption energy of oxygen on the surface. "Studying the factors affecting stability can specifically alleviate the degradation of BFCZY oxygen electrode, meanwhile, the activity and stability of the BFCZY oxygen electrode are significantly improved through heterointerface engineering by infiltrating the BCO catalyst." said Shaorong Wang.
Other contributors include Xiaoyu Zhang, Chenxiao Wang, Kui Liu, Ting Chen, Guangjun Zhang, Ning Sun, Zichen Zhuang, Lang Xu, from the School of Chemical Engineering & Technology at China University of Mining and Technology; Yucun Zhou from Beijing Huairou Laboratory, Zuzhi Huang from School of Materials and Energy at Jiangxi Science and Technology Normal University.
This work was supported by the National Key Research and Development Program of China (2021YFB4001502).
About Author
Professor Wang Shaorong has been engaged in the research of Solid Oxide Fuel Cells (SOFC) since studying for a doctoral degree in Japan in 1994. He has long been committed to the research on materials, cells, stacks and systems of SOFC/SOEC, as well as the industrialization and application of SOFC/SOEC. He has been funded as a "Double Innovation Talent" in Jiangsu Province and the chief of an innovation team, and supported as a leading talent in the construction of provincial advantageous disciplines and the "Double First-Class" construction of the university. Currently, he serves as a member of the National Standard Committee for Fuel Cells and Flow Batteries, a member of the Hydrogen Energy Professional Committee of the Chinese Renewable Energy Society, the director of the Fuel Cell Professional Committee of the Jiangsu Renewable Energy Society, and an editorial board member of the Journal of Ceramics. He has presided over the adoption of standards for testing SOFC single cells/stacks and participated in the formulation of multiple standards. He has undertaken a number of scientific research projects related to SOFC, including national 863 Program projects, national key research and development program projects and topics, key projects and general projects of the National Natural Science Foundation of China, key projects of the Jiangsu Provincial Natural Science Foundation, and carbon neutrality projects. He has published more than 180 scientific research papers in Adv. Funct. Mater., Appl. Catal. B-Environ., Energy Storage Mater., Chem. Eng. J., Sep. Purif. Technol., J. Power Sources, etc., authorized more than 20 invention patents, published 3 monographs, and has been selected into the list of highly cited authors in the energy field by Elsevier for 4 consecutive years. He has cultivated more than 50 master's and doctoral students.
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 2024 IF is 16.6, ranking in Top 1 (1/33, Q1) among all journals in "Materials Science, Ceramics" category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
