Experimental method to determine the changes of Ni content in operated SOFC anodes

The performance of an anode supported SOFC during operation depends on the stability and reliability of the cell components vs. time. This paper focuses on the anode with special attention given to the active part at the interface with the electrolyte. An original method to quantify the local Ni content in the anode of solid oxide fuel cells is presented and documented with examples coming from its application on button cells aged in various conditions of fuel utilization and temperature. The results are compared with the original Ni amount in a as sintered state (i.e. green) cell, and a freshly reduced (i.e. pristine) cell. The collected data describes with cost effective method the Ni content in the first 10 μm from the electrolyte and then in the remaining part of the anode. The first results obtained on operated and pristine cells has shown an initial Ni depletion homogeneously distributed on the whole volume. Important differences were noticed in cells operated for a few hundred hours especially in the active zone of the anode. The method uses the quantitative data in weight percent obtained by a calibrated EDXS coupled with an SEM from frames recorded at 5000x of magnification (total corresponding area of 3018.75 μm2) of a polished cross section of the anode. Adjacent areas from the interface with the electrolyte to the edge of the anode are analyzed. The method presented in this paper renders sensitive to local variations in the Ni content once the Zr content is assumed unaffected by cell production and cell operation.