Investigation of transition metal-doped BaCe0.8Y0.2O3-δ cathodes for protonic ceramic fuel cells: Microstructural and electrical properties

Protonic ceramic cathodes have emerged as a vital component for enhancing the efficiency and performance of protonic ceramic fuel cells (PCFCs) due to their excellent protonic conductivity and intermediate operation temperature. In this work, the doping effect of transition metals in BaCe_0.8X_0.1Y_0.1O_3-δ (X = Ni, Co, and Cu, BCXY) perovskites was systematically investigated. The phase analysis via X-ray diffraction (XRD) studies confirmed the development of single-phase perovskite for all doped samples. Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) were employed to examine the surface morphology, revealing clear and well-defined crystallites. TEM mapping further demonstrated the uniform dispersion of dopants, indicating successful synthesis. X-ray photoelectron spectroscopy (XPS) further validates the elemental composition and purity of the samples. The lowest area-specific resistance (ASR) values were obtained for BCCuY at 750 °C, measuring 0.21 Ω·cm² in dry air and 0.17 Ω·cm² in wet air. The activation energies in wet air atmosphere were found to be in the order of BCCuY (0.64 eV) < BCCoY (0.76 eV) < BCNiY (1.12 eV), within the temperature range of 600 to 750 °C, suggesting that BCCuY has the lowest activation energy and potentially better catalytic activity in these conditions. Considering these results, BCCuY perovskite shows promise as a protonic ceramic cathode for PCFCs. The long-term chemical compatibility evaluation was performed at 800 °C for 100 hrs, which showed that all three electrode materials are chemically compatible with BCZY electrolyte. This work shows the strategy of doping transition metals in BaCeO_3-δ-type oxides could be of great interest for the successful development of novel oxygen electrodes for PCFCs.