CO2-stable alkaline-earth-free solid oxide fuel cells with Ni0.7Co0.3O-Ce0.8Sm0.2O1.9 composite cathodes

One of the main problems for the deployment of intermediatetemperature solid oxide fuel cells (IT-SOFCs) is their chemical stability, since most of SOFCs contain alkaline-earth metal elements (Ba, Sr and Ca) that easily react with CO2 forming carbonates. To tackle this problem, we performed a systematic investigation of a series of Ni0.7Co0.3O-Ce0.8Sm0.2O1.9 (NC3OSDC) composite cathodes, which are CO2-stable and alkalineearthfree compounds. In this work, NC3O-xSDC (with x = 0-60 wt.%) samples were synthesized by self-propagating combustion method and investigated as new cathode materials for oxygen-ion conducting SOFCs. The thermal stability and phase structure of NC3O polycrystalline powders were studied using TG-DTA and XRD analysis, which confirmed that NC3O is chemically compatible with SDC. The electrical conductivity and thermal expansion of the NC3O-xSDC samples were measured. The electrochemical properties of NC3O-xSDC/SDC/NC3O-xSDC cells were studied using electrochemical impedance spectroscopy measurements. Among the NC3O-xSDC series, NC3O-30SDC showed a minimum in cathode polarization resistance, being 0.071 Ω cm2 at 800°C. A maximum power density of 200 mW/cm2 at 600°C was obtained using anode-supported SOFCs.