Effects of Electrode Microstructure on Polarization Characteristics of SOFC Anodes

Anode microstructure parameters were quantified by SEM-EDX measurements and the dependence of polarization characteristics on the anode microstructure parameters is investigated experimentally. Nickel yttria-stabilized zirconia (Ni-YSZ) anode supported cells with a thin YSZ electrolyte, lanthanum-strontium-manganite (LSM)-YSZ composite cathode, and LSM cathode current collector layers were fabricated by dip coating method. Anode microstructure was successfully imaged and quantified by ultra low voltage SEM and by means of stereology. Cell voltage measurements and impedance spectroscopy were performed at 650 and 750°C with hydrogen diluted by nitrogen as a fuel. A quantitative relationship between measured polarization and microstructure parameters, e.g., three phase boundary length, contiguity, etc., was discussed. Finally, a cell with an anode functional layer (AFL) was fabricated to investigate the possibility of improving both activation and concentration polarization characteristics.