Synthesis and electrochemical properties of La 1.6Sr 0.4Ni 1-xCu xO 4 as cathode materials for intermediate temperature solid oxide fuel cells

Abstract

Cathodic materials La 1.6Sr 0.4Ni 1-xCu xO 4 (x=0.2, 0.4, 0.6, 0.8), for an intermediate temperature solid oxide fuel cell (IT-SOFC), were prepared by a glycine-nitrate process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Results showed that no reaction occurred between the La 1.6Sr 0.4Ni 1-xCu xO 4 electrode and the Ce 0.9Gd 0.1O 1.95 (CGO) electrolyte at 1000°C, and that the electrode formed good contact with the electrolyte after sintering at 1000 °C for 4 h. Electrochemical AC impedance spectroscopy measurements were used to study cathodic performance. The La 1.6Sr 0.4Ni 0.4Cu 0.6O 4 cathode gave the lowest polarization resistance (Rp) of 0.35 Ω·cm 2 at 750° C in air. Electrode properties of La 1.6Sr 0.4Ni 1-xCu xO 4 were studied under various temperatures and oxygen partial pressures. The two main oxygen reduction processes at the cathode are the oxygen ion transfer from the triple phase boundary to CGO electrolyte, and the charge transfer process. Charge transfer is the major rate limiting step for La 1.6Sr 0.4Ni 1-xCu xO 4 cathode. The La 1.6Sr 0.4Ni 0.4Cu 0.6O 4 cathode exhibited the lowest overpotential, about 45 mV for a current density of 45 mA·cm -2 at 700°C in air. This preliminary work showed that the present La 1.6Sr 0.4Ni 1-xCu xO 4 materials may be potential cathodes for use in IT-SOFCs. © Editorial office of Acta Physico-Chimica Sinica.