Parametric study of Ni-GDC based electrolyte-supported cell via electrochemical impedance spectroscopy

Ni-GDC based electrolyte-supported cell (ESC) has become one of the mature solid oxide fuel cell (SOFC) types, due to its superior mixed ion-electron conductivity. However, there is limited understanding concerning the different electrochemical processes during operation, which is essential for long-term operation and various industrial applications. This study aims to separate the electrochemical processes in Ni-GDC based ESC within the effective frequency range via electrochemical impedance spectroscopy (EIS) measurements. Different parameters have been tested, including current density, temperature, and partial pressure of H 2 , H 2 O, and O 2 . A parametric sensitivity of the distribution of relaxation time (DRT) was analyzed to differentiate the gas conversion (0.1–1 Hz), O 2 − surface exchange in GDC (0.1–10 Hz), negatrode/positrode gas diffusion partially coupled with O 2 − surface exchange (1-50 Hz) and charge transfer at the negatrode triple phase boundary (TPB) and air electrode (50-150 Hz and > 150 Hz). The DRT results were cross-validated by the RQ based equivalent circuit model (ECM) and the corresponding complex nonlinear least squares (CNLS) fit, which also quantified the resistance of different electrochemical processes. This study provides guidelines for internal cell configuration optimization and insights into the operando diagnostics of Ni-GDC based ESC technology.