Stable, efficient and cost-competitive Ni-substituted Sr(Ti,Fe)O3 cathode for solid oxide fuel cell: Effect of A-site deficiency

Abstract In this work, a cost-competitive oxide system of Ni-substituted Sr1-xTi0.3Fe0.6Ni0.1O3-δ (STFN, x = 0, 0.02, 0.05), is evaluated as Solid Oxide Fuel Cell cathode. All STFN oxides present cubic perovskite structure with maximum conductivities over 22 S/cm in air. The introduction of Sr deficiency yields higher oxygen vacancy and lower thermal expansion coefficient. As a result, the cathode polarization resistance of 0.107 Ω cm2 is obtained for Sr0.95Ti0.3Fe0.6Ni0.1O3-δ (STFN-95) at 750 °C and p O 2 = 0.21 a t m , with weak oxygen partial pressure dependence. Specially, STFN-95 presents higher stability with slower R p increasing rate in lower oxygen partial pressure of 0.14 atm than in 0.21 atm, which greatly facilitates the cathode practical application in SOFC stack under high air utilization condition. Finally, a stable operation of 400 h is achieved using STFN-95 cathode on anode supported single cell at 750 °C, without showing Sr and other elements diffusions.