Enhanced electrochemical behaviour and lower thermal expansion in Pr-doped SrFeO3-δ for symmetric SOFC electrodes.

Abstract

Perovskite-type oxides, with the general formula Pr1-xSrxFeO3-δ (x = 0.2, 0.4, 0.6, 0.8), have emerged as promising candidates for symmetric solid oxide fuel cell (SSOFC) electrodes due to their high mixed ionic-electronic conductivity, chemical stability, and low polarization resistance. These properties make them suitable for improving the efficiency and sustainability of fuel cell systems. In this work, we investigate the influence of different Sr and Pr contents with the main objective of stabilizing these materials under reducing conditions, enabling their use as both anode and cathode. Enhancing electronic conductivity while minimizing polarization resistance is a key goal. The materials were synthesized via the freeze-dried precursor method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). All synthesized compositions exhibited single-phase cubic perovskite structures. XPS analysis revealed multiple oxidation states for praseodymium (Pr3+4+) and iron (Fe2+/3+/4+). The most favourable electrochemical performance was observed for Pr0.4Sr0.6FeO3-δ in air and Pr0.6Sr0.4FeO3-δ in 100% H2, showing polarization resistance values as low as 0.15 Ω·cm2 in air and 0.09 Ω·cm2 in 100% H2 at 700 °C.