Proton-conducting electrolytes for high-performance ceramic electrolysis cells: Materials, mechanisms, modification, and process

Protonic ceramic electrolysis cells (PCECs) have attracted significant attention as promising technologies for efficient and low-carbon hydrogen production, owing to their unique proton transport mechanism and operation in the intermediate-temperature range (400–700 ℃). However, current proton-conducting electrolytes (PCEs) still suffer from limited proton conductivity, insufficient chemical stability, high grain-boundary resistance, and difficulties in densification, which severely restrict their practical application. This review presents a systematic examination of recent advancements in PCE materials, covering both classic perovskite systems and emerging non-perovskite oxides, while establishing a fundamental framework of the proton conduction mechanisms and degradation pathways of PCEs. Building upon the mechanistic insight, typical modification strategies for high-performance PCEs are summarized, including elemental doping, non-stoichiometric control, and machine learning. Furthermore, advanced fabrication methods and sintering process of thin-film and dense PCEs are thoroughly discussed. The review particularly highlights the essential interplay between material selection, chemical modifications, and process optimization in developing high-performance PCEs, providing a comprehensive perspective and practical guidance for the practical application of PCEs.