Enhanced PCFC performance via anode additive BaCO3–Induced grain growth in BZYb electrolyte

This study explores Ba diffusion sintering as a novel method to enhance the densification and microstructural properties of BaZr_0.8Yb_0.2O_3–δ (BZYb20) electrolytes for proton-conducting fuel cells (PCFCs). By adding BaCO₃ to the anode and optimizing sintering conditions, significant improvements in electrolyte grain growth and densification are achieved. The sintering mechanism, driven by chemical potential gradients of Ba, Ni, and Yb, involves element migration toward the electrolyte surface and the formation of a Ba–Ni–O phase. Ba diffusion plays a central role, with Ni evaporation and reverse Ba migration contributing to improved microstructure, while Yb diffusion at elevated temperatures leads to porous structure formation. This approach enables the synthesis of dense electrolytes with a uniform grain size of 4–5 μm, doubling proton conductivity compared to BaCO₃–free samples. However, excessive anode densification reduces the H₂ supply, which is mitigated by adjusting the NiO–BZYb ratio from 60:40 to 80:20, yielding a peak power density of 0.85 W cm⁻² at 600 °C. The findings highlight Ba diffusion's critical role in controlling microstructure and optimizing PCFC performance, providing a foundation for further sintering optimization.