YI Ziheng ¹, XU Xu ¹, WANG Hao ¹, LU Haotian ¹, WANG Leying ¹, LUO Linghong ¹,

CHENG Liang ², XIONG Bin ¹, CAO Xiwen ¹

(1. School of Materials Science and Engineering, Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China;

2. National Engineering Research Center for Domestic & Building Ceramics, Jingdezhen Ceramic University,

Jingdezhen 333403, Jiangxi, China)

Extended abstract:

[Significance] Solid oxide cells represent a highly efficient technology for electrochemical energy conversion and storage, yet their widespread application is hindered by the challenge of synergistically optimizing the catalytic activity, long-term stability, and fuel adaptability of fuel electrodes. Conventional nickel-based electrodes are susceptible to coking, sulfur poisoning, and insufficient redox stability, while perovskite mixed ionic-electronic conductors often suffer from intrinsically low catalytic activity. In this context, the in-situ exsolution strategy has emerged as an innovative electrode design approach. This strategy involves pre-doping target active metal elements into the B-site of a perovskite lattice, followed by inducing their migration from the lattice interior and in-situ precipitation under a reducing operating atmosphere, thereby constructing a structurally robust and functionally synergistic "metal-oxide" heterointerface on the perovskite substrate. This review systematically elaborates on the fundamental thermodynamic and kinetic principles of the in-situ exsolution strategy and provides an in-depth analysis of the unique advantages and synergistic catalytic mechanisms of the constructed heterointerfaces. The exsolved metal or alloy nanoparticles often form a strongly coupled epitaxial interface with the perovskite support. This not only effectively anchors the nanoparticles and suppresses their high-temperature agglomeration but also significantly enhances the overall electrocatalytic performance of the electrode through the synergy between the metal sites (providing catalytic activity) and the oxide support (providing oxygen vacancies and ion transport pathways). Moreover, the excellent redox reversibility of this interface, where the metal nanoparticles can undergo reversible exsolution and re-dissolution in response to atmospheric changes, laying the foundation for the dynamically stable operation of reversible solid oxide cells.

[Progress] Regarding applications, the review provides a detailed summary of the latest research progress of this strategy in fuel electrodes for solid oxide fuel cells, electrolysis cells, and reversible cells. For SOFCs, anodes developed by designing the exsolution of multicomponent alloys (e.g., NiFe, CoFe) or core-shell structures have demonstrated high power density and exceptional resistance to coking and sulfur poisoning in fuels ranging from hydrogen and hydrocarbons to ammonia. For SOECs, the heterointerface of perovskite cathodes has been optimized through A-site deficiency, elemental doping (e.g., Sn, Cu), or dynamic redox treatments, enabling high-current-density CO₂ electrolysis and demonstrating good stability in impurity-containing atmospheres. For RSOCs, leveraging the reversible nature of the exsolved interface, bifunctional fuel electrodes have been successfully developed that maintain high activity and cyclic stability during repeated switching between fuel cell and electrolysis modes.

[Conclusions and prospects] Despite the significant achievements of the in-situ exsolution strategy, its path toward large-scale practical application still faces multiple challenges. Future efforts should focus on the following key areas: (1) developing more precise in-situ characterization techniques to uncover the dynamic evolution of heterointerfaces; (2) develop large-scale electrode fabrication technologies compatible with the production of large-area cells (e.g., tape casting), and establish precise and controllable reduction heat treatment techniques; and (3) leveraging artificial intelligence (AI) to assist in material screening and design.

Key words: solid oxide cells; in-situ exsolution; perovskite fuel electrode; heterogeneous interface