Space Charge Polarization Effect in Surface-Coated BaTiO₃ Electrolyte for Low-Temperature Ceramic Fuel Cell

The significant enhancement of ionic conduction in semiconductors as potential electrolytes for low-temperature ceramic fuel cells (LT-CFCs) has recently gained strong attention. This study introduces a surface coating of CeO₂ on the dielectric perovskite material BaTiO₃ (BTO) to function as an electrolyte for LT-CFC applications. The 10% CeO₂ coated on BTO (BTO-10CeO₂) exhibited an open-circuit voltage (OCV) of 1.05 V and a power density of 609 mW cm^-2 at 550 °C. Integrating BTO and CeO₂ at the interfaces and the induced built-in electric field (BIEF) establishes a rapid ion-conducting pathway, thereby facilitating the BTO-10CeO₂ composite to exhibit a high ionic conductivity of 0.18 S cm^-1. At an applied frequency of 20 kHz, the maximum dielectric constant of BTO-10CeO₂ was approximately 5800 at 550 °C, and the maximum temperature (T_m) showed a reversible proportionality to the applied frequency in an air environment. The consistently high ionic conductivity (σ_o) of BTO-10CeO₂ across various applied frequencies underscores the role of dielectricity and polarization in accelerating ion transport. This observation provides crucial insights into how dielectric properties and polarization effects impact ionic transport, laying the foundation for further optimization and advancement in ceramic fuel cell technology.