| 초록 |
There are many factors limiting the electrochemical performance of planar solid oxide fuel cells (SOFCs) on the level of a large area stack that are usually not detected on the level of a button cell. The performance of SOFC stack strongly depends on the operating conditions. Hydrogen fuel is consumed and water is produced at the anode side by an electrochemical reaction, thus anode gas-phase transport has a large impact on the SOFC performance depending on fuel utilization. In a planar-cell channel-type setup, the fuel gas flows along the anode gas channel length, parallel to the anode surface at a finite gas flow rate so that concentration gradients are established from the gas inlet to the outlet region because of fuel depletion. Consequently, it is not expected that the electrochemical reaction will occur evenly throughout the active area of the cell. Thus, the problem of how to enhance the gas exchange between the hydrogen and water above the anode in order to minimize the concentration gradient (voltage loss and/or degradation) should be considered. Another SOFC stack degradation phenomenon is the abnormal operation of a cell with cell voltage becoming negative. Cell imbalance in a series-connected stack causes abnormal operation under negative cell voltage, and consequently rapid degradation by anode interface delamination. Several principal degradation mechanisms of SOFC stack are discussed. |
