Electrochemical Degradation of Fuel Cells: Effect of Electrolyte Composition

Abstract

Recently, a model for SOFC stack degradation when a cell begins to operate under a negative voltage due to 'cell imbalance' was presented. Subsequently, experimental evidence for degradation was presented by investigating cell (stack) failure mechanism. When operated under a negative voltage of a sufficient magnitude, anode/electrolyte interface delaminated. The model shows that electronic conduction through the electrolyte plays a significant role. In the present work anode-supported cells were made of two different electrolyte compositions: (a) 8YSZ, (b) 92% 8YSZ + 8% CeO2 (8CYSZ). It was observed that when operated under a negative voltage, the cell with 8YSZ exhibited considerable degradation attributed to electrolyte/anode interface delamination. By contrast, the cell with 8CYSZ exhibited no degradation under similar testing conditions. Results are explained on the basis of electronic conduction and the previously described degradation model.