A perspective paper of the E-MRS 2025 spring meeting (Symposium K: “Solid state ionics: Functional materials and devices for electrochemical energy conversion and storage applications”)

This prospective paper introduces a new publication format that connects the immediacy of conference reporting with the depth of expert analysis. It summarizes contributions and discussions from the E-MRS 2025 Spring Meeting Symposium K on “Solid state ionics: functional materials and devices for electrochemical energy conversion and storage applications ” , highlighting recent advances and open challenges in the field. This paper focuses on three major research directions related to protonic ceramics: (1) the positrode (air/steam electrode): after discussing the mechanistic aspects of the oxygen reduction, various strategies are proposed to develop high-performance positrode materials; (2) the sealant: adequate sealing materials need to be developed for protonic ceramic cells to accommodate for the chemical expansion upon hydration; (3) membrane reactors: in addition to being used for fuel cells and elecrolysers, protonic ceramics can be integrated in membrane reactors for (de)hydrogenation reactions, synthesis of high-value-added chemicals, and CO₂ utilisation. • Protonic ceramic positrode mechanism and architecture are discussed. • Machine learning is proposed as a tool to develop new positrode materials. • New sealing materials are proposed for protonic cells. • Overview of membrane reactors based on protonic ceramics is given.