Multiscale engineering of BaZr1-xYxO3-δ -based protonic ceramics: A critical review of defect chemistry, interface design, and computational insights

Protonic ceramic energy devices represent a promising frontier for sustainable energy conversion and storage, operating efficiently at intermediate temperatures (350–650 ​°C) and facilitating integration with renewable energy sources. Among protonic ceramic materials, yttrium-doped barium zirconate (BaZr1-xYxO3-δ, BZY) stands out for its competitive proton conductivity, chemical resilience, and compatibility with diverse fuels and environments. This review critically examines the fundamentals and multiscale design strategies for BZY-based ceramic cells. We discuss atomic-level composition-structure relationships, innovative synthesis routes, and advanced processing methods to overcome manufacturing and scalability challenges. We then highlight microstructure engineering and interface design approaches that minimize resistance and elevate device performance, supported by state-of-the-art characterization and predictive modeling techniques, including density functional theory and machine learning. Recent advances, such as hybrid architectures and AI-driven defect optimization, demonstrate significant improvements in conductivity, stability, and Faradaic efficiency, confirming BZY's pivotal role in green hydrogen production and power-to-chemicals applications. By integrating insights across materials chemistry, electrochemistry, and engineering, this review provides a comprehensive roadmap for researchers aiming to translate laboratory breakthroughs into robust, scalable protonic ceramic technologies for decarbonized energy systems.