Effects of rare earth doping on electrochemical properties of NdBaCo2O6- cathode materials

Abstract

Abstract Nd0.9Ln0.1BaCo2O6-δ (NLnBCO, Ln = La, Sm, Gd) materials are synthesized by EDTA-citrate method. The effects of rare earth element doping on crystal structure, thermal expansion behavior, electrical conductivity and electrochemical properties are investigated. Nd0.9Ln0.1BaCo2O6-δ crystallizes in tetragonal symmetry with the space group P4/mmm. It is found that both the unit cell volume and the average valence of cobalt in NLnBCO increase, whereas the oxygen vacancy content (δ value) decreases with the gradual enlargement of the radius of the doped rare earth elements. XPS and O2-TPD results prove that the surface oxygen adsorption ability of NLnBCO improves gradually with the steady increase of Co4+ concentration in the material. The electrochemical impedance spectroscopy measurement results indicate that among the doped materials, Nd0.9La0.1BaCo2O6-δ exhibits the lowest polarization resistance of 0.083 Ω cm2 at 700 °C in air. The anode-supported fuel cell constructed with this cathode shows a power output of 1.045 W cm−2 at 700 °C, and stable current density of 1.7 A cm−2 has been obtained with the load of 0.6 V for prolonged 100 h consecutive measurement. The rate limiting step of the oxygen reduction reaction (ORR) is the charge transfer process on Nd0.9La0.1BaCo2O6-δ cathode. Our studies prove that doping La3+ with larger radius than Nd3+ is an effective way to promote the ORR reaction on NdBaCo2O6-δ cathode.