Experimental investigations of cell resistances to characterize the concentration polarization behavior of 10 ×10 cm2 solid oxide fuel cells

High fuel utilization rate is the basis for solid oxide fuel cells (SOFCs) to achieve high power generation efficiency. However, the severe concentration polarization, namely limiting current behavior, hinders cell performances in the situation of high utilization rates. In this work, a planar SOFC with 10 × 10 cm 2 working area is tested using both voltammetry and electrochemical impedance spectroscopy (EIS) at various air and fuel flow rates. Cell resistance is obtained from the smoothed derivatives of voltage vs. current curves as well as the Nyquist plots of EIS results. It is found that resistance vs. current plots reveal the limiting current behavior better than voltage vs. current curves. It is indicated that cell resistance is a more suitable and robust criterion for the limiting current behavior of fuel cells. It is also found that the high reactant utilization rate leading to the limiting current behavior is stable. This finding can provide useful information about fuel sensitivity analysis. Overall, cell resistance is a useful indicator that quantitatively describes the working status of SOFCs. Setting a resistance threshold is a good option to maintain safe and healthy operating status, especially for industrial SOFCs. • Cell resistances are used as criterions for the limiting current behavior of SOFCs. • Cell resistances can quantitatively describe the working status of SOFCs. • A resistance threshold can guarantee the healthy operation of SOFCs. • Reactant utilization rates that lead to cell limiting current behavior are stable.