Optimization electrochemical performance and thermal compatibility via SmBa 0.5 Sr 0.5 CoCuO 5+δ and Ce 0.9 Gd 0.1 O 1.95 composite cathodes for intermediate-temperature solid oxide fuel cells

The SmBa0.5Sr0.5CoCuO5+δ- $$x$$ Ce0.9Gd0.1O1.95 ( $${\text{SBSCCo}}-x{\text{GDC}}$$ , $$x$$  = 20–50 wt%) composite cathodes are prepared by physical mixture. Its properties are investigated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The X-ray diffraction (XRD) spectra show that there are no chemical reaction between SBSCCo cathode and GDC electrolyte after co-sintered at 950 °C for 10 h and 800 °C for 100 h, respectively. With the increase of GDC weight ratio, the thermal expansion coefficient (TEC) of $${\text{SBSCCo}}-x{\text{GDC}}$$ composite cathodes is obviously reduced. The TEC of SBSCCo-50GDC is reduced to $$13.14 \times 10^{ - 6} {\text{ k}}^{{ - 1}}$$ from 30 to 850 °C. The conductivity of $${\text{SBSCCo}}-x{\text{GDC}}$$ composite cathodes shows the characteristic of transition from semiconductor to metal with increased temperature. The addition of GDC into SBSCCo cathode significantly improves the catalytic activity of $${\text{SBSCCo}}-x{\text{GDC}}$$ composite cathodes. The polarization resistance of SBSCCo-30GDC composite cathode on GDC electrolyte reaches 0.022 $$\Omega {\text{cm}}^{2}$$ at 800 °C in air. During the stability test, the polarization resistance of SBSCCo-30GDC composite cathode increased by 9.8% in 80 h. The maximum power density of fuel cell with SBSCCo-30GDC composite cathode on 0.3-mm-thick GDC electrolyte reaches 662 mW cm−2 at 800 °C. These primarily results suggest that $${\text{SBSCCo}}-30{\text{GDC}}$$ composite cathode is a promising cathode material for IT-SOFCs.