Advanced electrochemical properties of Pr0.9Y0.1BaCo1.8Ni0.2O6-δ - Ce0.8Sm0.2O1.9 composite as cathode material for IT-SOFCs

The co-doped double perovskite-type cobaltite Pr0.9Y0.1BaCo1.8Ni0.2O6-delta (PYBCN) is synthesized via organo-metallic precursors. The concentrations of electronic and ionic defects in PYBCN at variations of gaseous environment are obtained from the analysis of the experimental isothermal plots for equilibrium oxygen content (6 - delta) vs. oxygen partial pressure P-O2, in the ambient gaseous phase. It is argued that nickel doping is beneficial for enhanced formation of vacancies in O2- positions controlling oxygen ion transport in the cobaltite. The cobaltite based dual-phase composite with 30 wt% addition of samarium doped ceria Ce0.8Sm0.2O1.9 (SDC) is found to have considerably reduced thermal expansion compared to the parent cobaltite. The impedance measurements show that the area specific resistance (ASR) of the composite decreases to 0.11 Omega cm(2) at 973 K with the activation energy 1.2 eV. Further increase of the temperature is accompanied by the decline of the activation energy to 0.9 eV, and ASR attains 0.045 Omega cm(2) at 1073 K. The observed small ASRs are attributed to a large concentration of O2-vacancies in the cobaltite component of the composite. The cathodic overvoltage for oxygen reduction that does not exceed 40 mV at 1073 K and current density 1000 mA cm(-2), moderate thermal expansion, good conductivity and high electro-chemical activity distinguish the developed composite as one of the promising cathode materials for intermediate temperature solid oxide fuel cell applications. (C) 2018 Elsevier B.V. All rights reserved.