High-performance SrFe0.1Mo0.9O3-δ -based composites for the anode application in solid oxide fuel cells

Abstract The present work reports the electrochemical performance of the composites formed by SrFe0.1Mo0.9O3-δ and Gd0.1Ce0.9O2-δ for their possible anode application in solid-oxide fuel cells. Phase analysis reveals the absence of impurity phase on thermally treating the mixture at 950 °C in both oxidising and reducing conditions. The DC-electrical conductivity of the dense composite sample is metallic in nature with the magnitude of ~42.2 S cm−1 at 850 °C under reducing conditions. The electrode area-specific resistance is measured by performing two-probe impedance spectroscopy on symmetrical cells with Gd0.1Ce0.9O2-δ coated YSZ as an electrolyte from 700 °C to 850 °C. Porous electrodes with the compositions of xGd0.1Ce0.9O2-δ/SrFe0.1Mo0.9O3-δ (where x is a wt. fraction of Gd0.1Ce0.9O2-δ with the value of 0, 0.5, 0.6, 0.7 and 0.8) are fabricated by blade-coating the ceramic slurries and subsequently sintering at 950 °C for 1 h in air. The symmetrical cells with the composite electrode of 0.7Gd0.1Ce0.9O2-δ/SrFe0.1Mo0.9O3-δ exhibit an extremely low electrode area-specific resistance of ~0.086 Ω cm−2, which is nearly one-third of the magnitude shown by cells with pure SrFe0.1Mo0.9O3-δ as electrodes at 850 °C in 3% H2O/H2. Introducing higher porosity-level in the optimised composite electrode further reduces this value to ~0.06 Ω cm−2. However, not much effect has been observed on increasing the pore-former amount above 30 wt% of the electrode material. The overall activation energy for the polarisation resistance in 0.7Gd0.1Ce0.9O2-δ/SrFe0.1Mo0.9O3-δ is in the range of 0.4–0.5 eV. The impedance analysis indicates that adding the electrolyte phase of Gd0.1Ce0.9O2-δ in SrFe0.1Mo0.9O3-δ significantly enhances the kinetics of processes relating to the hydrogen-oxidation reaction occurring in the electrode. The exceptional performance of the Ni-free ceramic composite electrodes developed in the present work without employing expensive and labour-intensive infiltration technique for fabrication highlights the exciting prospects of Gd0.1Ce0.9O2-δ/SrFe0.1Mo0.9O3-δ composite as an anode material for SOFCs.