Enhancement of electrochemical performance of SrFe0.5Co0.5O3-δ as air electrode for intermediate temperature solid oxide cells via Sb and Mo doping

Optimisation of the composition or rare-earth-free perovskites is of considerable interest for their application as air electrodes in intermediate temperature solid oxide cells (IT-SOCs). Herein, we report the effects of Mo and Sb doping (5 mol %) of SrFe0.5Co0.5O3-δ (SFC) on oxygen content, thermal behaviour, electrochemical properties and stability. Phase-pure, XRD-cubic perovskite is achieved on sintering powder derived from Pechini synthesis in the range 1000-1100 °C for SFC, SrFe0.475Co0.475Mo0.05O3-δ (SFCM) and SrFe0.475Co0.475Sb0.05O3-δ (SFCSb). Oxygen content determined by redox titration is greater for the Mo- and Sb-doped phases than for SFC, although oxygen loss occurring at > 350 °C is greatest for SFCSb. The higher total oxygen content of the Mo-doped phase is expected to increase the electron-hole content resulting in higher conductivity (σ = 340.5 S cm−1 at 300 °C in O2). In contrast, the greater oxygen-vacancy content with increasing temperature of the Sb-doped material is associated with the most competitive electrode-polarisation resistance (<0.1 Ω cm2 at 700 °C). The greater relative effect of cathodic and anodic polarisation on improving electrochemical performance at lower temperatures highlights the potential of the studied compositions as air electrodes in IT-SOCs.