Investigations into the Degradation of the Cermet Anode of a Solid Oxide Fuel Cell

Abstract

Today's SOFC membrane electrolyte assemblies produced within the Siemens SOFC development program and tested in mixtures of water vapor with hydrogen or methane show a long-term degradation of 20 mu V/h. This is still 10 times the rate required for a commercial application. As optical and electron micrographs of aged cells reveal, the nickel within the porous cermet structure of the anode disappears partially and accumulates in cracks of the cermet or on surfaces in the surrounding. It is concluded that nickel is transported via gaseous species. Thermodynamic calculations suggest that this is due to the volatile hydroxide Ni(OH)(2) and that the effect is enhanced by a high oxygen activity in the fuel.