Degradation Behavior of Solid Oxide Fuel Cells Operated at High Fuel Utilization

Abstract

High energy conversion efficiency in solid oxide fuel cell (SOFC) systems can be achieved by improving the fuel utilization. However, an operation at high fuel utilizations negatively affects Ni-based cermet anodes; the downstream part of the anode is exposed to high P(O2) atmospheres due to the depletion of fuel and the high steam concentration. At this stage, no reports dealt with the degradation phenomena of the anode under such severe conditions. In this study, we aimed to clarify degradation phenomena at the downstream part of practical cells operated at high fuel utilizations by using bottom cells. Fuel gases simulated severe conditions were supplied to single cells. The change in electrochemical properties was monitored during discharge operation, and the microstructural evolution of the anode was quantitatively analyzed by the focused ion beam–scanning electron microscope (FIB–SEM) technique.