Electrode surface engineering for proton-conducting ceramic cells: Advances and perspectives

Proton-conducting ceramic cells (PCCs) enable high-efficiency energy conversion and storage at intermediate temperatures (400–600 °C) while offering lower operational costs and improved durability compared to oxygen-ion-conducting cells. However, their adoption is limited by their low electrocatalytic activity and high polarization resistance. Electrode surface modification has emerged as a compelling strategy for improving electrode activity and durability. This Review examines three approaches that have demonstrated performance enhancements in PCCs: (1) infiltration of catalytically active materials into a porous electrode scaffold, (2) exsolution of metallic and oxide phases under tailored redox conditions to generate active sites, and (3) pulsed laser and atomic-layer thin-film depositions for surface engineering. The fundamental mechanisms and crucial physical factors underlying each strategy are discussed, along with advanced characterization techniques that provide insight into the in situ growth, structural evolution, and phase transformation of active materials. Finally, we highlight the challenges associated with these techniques and recommend future research directions to accelerate the development of PCC technology for commercial applications.