A novel La₂NiO_4+Δ-La₃Ni₂O_7-Δ-Ce_0.55La_0.45O_2-Δ ternary composite cathode prepared by the co-synthesis method for IT-SOFCs

A novel La₂NiO_4+δ-La₃Ni₂O_7−δ-Ce_0.55La_0.45O_2−δ (L2N1-L3N2-LDC) ternary composite with a weight ratio of 0.3:2.5:2.2 was prepared by a one-step co-synthesis method and employed as cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). X-ray diffraction (XRD) profiles confirmed the successful synthesis of the composite consisted of L2N1, L3N2 and LDC phases, without any other impurity. Compared with the cathode prepared by the physical mixing method, the co-synthesized composite cathode possessed a porous microstructure with the smaller particle size and more uniform distribution of various elements. The ternary composite cathode on Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte revealed improved electrochemical performance, achieving the polarization resistance value of 0.06 Ω cm² at 800° C in stationary air. Electrochemical impedance spectra under various oxygen partial pressures indicated the charge transfer process was the rate limiting step for oxygen reduction reaction. Furthermore, a SDC electrolyte (about 350 μm) supported single cell with L2N1-L3N2-LDC as cathode and Ni-SDC as anode demonstrated a maximum power density of 253 mW cm⁻² at 800° C. These results confirmed that L2N1-L3N2-LDC ternary composite prepared by co-synthesized method is a very promising cathode material for IT-SOFCs.