Unveiling the potential of praseodymium oxide as efficient oxygen electrode for low-temperature solid oxide cell applications

Abstract

This study investigates praseodymium oxide (PrOx) as a promising oxygen electrode material for solid oxide cells operating below 600 °C. The electrode was fabricated using the spin-coating technique and characterized by XRD, XPS, XAFS, and DC conductivity measurements. Structural analysis enabled precise determination of the average oxidation state of praseodymium, revealing the presence of multiple PrOx phases, which significantly affect the material's electrochemical properties. Electrochemical impedance spectroscopy (EIS) indicated that a 200 nm electrode thickness yields optimal performance. The highest electrocatalytic activity for the oxygen reduction reaction was observed at an annealing temperature of 500 °C. The impact of water vapor (pH2O) and carbon dioxide (pCO2) on electrode performance was also examined. Both gases induced reversible changes, with the electrode retaining its activity—demonstrating superior stability compared to state-of-the-art materials. This change results from different structure and chemistry compared to perovskite oxides, higher redox activity associated with greater mobility of the Pr cation oxidation state, and lower basicity, which influences the formation of less stable carbonates and hydroxides. Full cell tests conducted at 500 °C yielded a power density of 95 mW·cm−2 - over four times higher and 39% greater than that of reference cells. These results highlight the potential of PrOx for use in solid oxide cells, proton-conducting cell technologies, and broader electrochemical applications.