Structure investigations of SOFC anode cermets - Part I: Porosity investigations

The number of electrolyte/metal/pore three-phase boundaries in the SOFC ano de cermet was determined in a cross-section photo according to the intercep ted-segment method and given as the volume concentration of the electrochem ically active phase boundary. The apparent geometrical exchange current den sity of hydrogen oxidation served as a relativizing measure of electrochemi cal activity. A direct correlation was found between the number of opticall y visible three-phase boundaries of 'electrolyte/nickel agglomerates/gas po res' in the unit volume of the electrode and the apparent electrochemical e xchange current density. The electrode was also analysed porosimetrically b y a standard porosimetry method (MSP) and the porosimetric curves were comp ared with the optical/electrochemical measurements of the same electrode. T his comparison revealed that the sum of the integrated volume of nickel agg lomerates and the single nickel particles in contact with the electrolyte g ive the total amount of the active nickel volume whose surface is directly proportional to the amount of optically visible three-phase boundaries in t he unit volume.