Structural and oxygen-transport studies of double perovskites PrBa_1-xCo₂O_5+δ (x = 0.00, 0.05, and 0.10) toward their application as superior oxygen reduction electrodes

Here we present a comprehensive study of oxygen-deficient double perovskites PrBa_1-xCo₂O_5+δ (x = 0.00, 0.05, and 0.10) to exploit their potential use as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Special attention is paid to the structure, oxygen concentration, and oxygen-ion transport properties, which are key factors related to the electrochemical performance. Based on the results obtained from a series of high-resolution structural analysis techniques, such as XRD, SAED, and HR-TEM, these double perovskite oxides possess tetragonal lattice symmetry and a stable crystal structure. According to the information obtained from iodometric titration, TGA, and O₂-TPD measurements, an increase in oxygen vacancy concentration in the lattice with an increasing Ba cation deficiency (x value) is demonstrated. Additionally, oxygen permeation flux and electrical conductivity relaxation (ECR) measurements illustrate an improved oxygen ionic conductivity, chemical bulk diffusion coefficient (D_chem) and chemical surface exchange coefficient (K_chem) with the introduction of Ba deficiency, likely due to the increase in the concentration of oxygen vacancies. Tests at 700 °C of the electrochemical performance based on symmetrical cells show area specific resistances (ASRs) of 0.045, 0.041, and 0.036 Ω cm² for PrBa_1-xCo₂O_5+δ with x = 0.00, 0.05, and 0.10, respectively. These results are extremely promising; consequently, these oxides are worthy of further study and optimization as cathode materials for IT-SOFCs.