Properties and electrochemical performance of Sr0.8La0.2TiO3−δ-Ce0.8Gd0.2O2−δ composite anodes for intermediate temperature solid oxide fuel cells

A series of Sr0.8La0.2TiO3−δ (SLT)-Ce0.8Gd0.2O2−δ (GDC) composite anodes with various volume ratios of SLT and GDC has been synthesized using a sucrose modified combustion technique. The percolation thresholds of Sr0.8La0.2TiO3−δ and Ce0.8Gd0.2O2−δ in the composite calculated based on the Kusy's percolation theory were 75.6 vol.% and 36.1 vol.%, respectively. While the rate of carbon deposition increased with an increase in the Ce0.8Gd0.2O2−δ content, the total electrical conductivity decreased in humidified H2 as well as in CH4. Based on the electrochemical performance measured using AC-impedance spectroscopy, the optimal anode composition was 65 vol.% Sr0.8La0.2TiO3−δ-35 vol.% Ce0.8Gd0.2O2−δ. This composite has polarization resistances of 2.80 Ω cm2 and 4.60 Ω cm2 in H2 and CH4, respectively, measured at 800 °C. Diffusion or concentration polarization was the rate determining steps for the fuel oxidation process in the Sr0.8La0.2TiO3−δ-Ce0.8Gd0.2O2−δ composite anode.