Optimized Pr1.6Ca0.4Ni1−yCuyO4+δ phases as promising electrode materials for CeO2- and BaCe(Zr)O3-based electrochemical cells

This study aims to optimize the Pr2NiO4+δ electrode material for increased phase stability at IT-SOFC operating temperatures while maintaining high electrochemical activity. This is achieved by double doping at both Pr and Ni sites. The series of new Pr1.6Ca0.4Ni1–yCuyO4+δ complex oxides are synthesized by the pyrolysis of the glycerol-nitrate compositions. The resulting materials are extensively studied by room and high-temperature XRD, XPS, TGA, SEM, dilatometry, DC-four probe method, and impedance spectroscopy. The study has registered the formation of the homogeneous complex oxide phases with an orthorhombic structure (Bmab sp. gr.) throughout the dopant concentration range of y = 0.0–0.4. For the Cu-rich samples, an increased Pr4+ content and the presence of Ni2+ and Cu+1 are observed, resulting in a gradual decrease of both the electroconductivity and the absolute oxygen content (δ ∼ 0 at y ≥ 0.2). Nevertheless, the Pr1.6Ca0.4Ni1–yCuyO4+δ series materials exhibit excellent phase stability and chemical and thermomechanical compatibility with CeO2- and BaCe(Zr)O3-based electrolytes. Moreover, Cu-doping enhances the electrochemical activity of the electrodes. The polarization resistance of the Pr1.6Ca0.4Ni0.8Cu0.2O4+δ electrode, is in the range of 0.19–0.27 Ω cm2 (at 700 °C) depending on the electrolyte substrate and shows a low dependence on the water content, demonstrating the applicability of the electrode in fuel cells and electrolysis cells based on both oxygen-ion and proton-conducting electrolytes.