Synthesis and Electrochemical Performance of Ni Substituted SrTi_(0.3)Fe_(0.7)O_(3-δ) Cathode: Effect of A-site Deficiency

摘要

Herein, we present the synthesis and electrochemical properties of Ni substituted Sr_(1-x)Ti_(0.3)Fe_(0.6)Ni_(0.1)O_(3-δ) (STFN, x=0; STFN-5, x=0.05) as solid oxide fuel cell cathodes. First, the results suggest a Ni solubility limit in SrTi_(0.3)Fe_(0.7)O_(3-δ), lower than ～14 at% in B-site. Second, the conductivities increase first with temperature increasing and then decrease; STFN shows a maximum conductivity of 23.9 S/cm at 700°C, while STFN-5 shows similar peak value but at much lower temperature of ～600-650°C. Third, the electrochemical impedance spectroscopy tests are conducted in a wide range of oxygen partial pressures below 0.21 atm, using symmetrical cells. The A-site deficient STFN-5 cathode shows smaller polarization resistance values compared with A-site stoichiometric composition. The polarization resistance of STFN-5 is ～0.11 Ω·cm~2 at 750°C in oxygen partial pressure of 0.21 atm and shows a relative stable operation during long term test in air.