- Research Article
- 10.1149/ma2025-03183mtgabs
How the Electrode Design Impacts the Impedance of Ceria-Based Fuel Electrodes
- Nov 24, 2025
- Electrochemical Society Meeting Abstracts
- Felix Kullmann + 3 more +3
Gadolinia-doped ceria (GDC) has been identified as a promising material for an application as a single-phase fuel electrode in solid oxide cells and receives interest for hydrogen operation [1-4] and CO2 electrolysis [5, 6]. The presence of both ionic and electronic conductivity as well as the electrocatalytic activity eliminates the need for an electronically conductive phase such as nickel and subsequently expands the active material-pore interface. But the rather high sintering temperature of GDC fuel electrodes, usually 1200 °C and above [2,4-8], results in a relatively coarse microstructure. Especially in low temperature applications, limited active surface areas cause significantly increased charge transfer reaction resistances.In this study, a physicochemically motivated impedance model based on a transmission line model [1, 3] is applied in order to optimize the electrode design of a single phase GDC fuel electrode that is contacted by a nickel current collector. The model is parametrized employing three different techniques as illustrated in figure 1 and is described in detail in Ref [3]. Details about the manufacturing of the GDC electrode can be found in [1].Four-point probe method is conducted in order to obtain the conductivity of GDC in a wide range of temperature und oxygen partial pressure (fig 1 a). Additionally, non-stoichiometry data [9] were used to separate the electronic and ionic conductivity and to calculate the chemical capacity of GDC. Focus ion beam tomography (fig 1 b) and electrochemical impedance spectroscopy (fig 1 c) were performed at four different GDC microstructures in order to reveal the microstructural parameters as well as the gas diffusion and charge transfer reaction impedance. The use of four distinct GDC microstructures for the parametrization and validation of the model ensures a high reliability for subsequent simulations.Figure 2 presents a simulation of the electrode impedance with different GDC microstructures. The microstructure is varied by simulating the microstructural parameters of GDC electrodes sintered at temperatures between 1300 °C and 1000 °C in 50 K steps. Two microstructures at the lowest and highest temperature are exemplary shown in (a) to visualize the coarsening towards higher temperatures. The simulation of the impedance and DRT spectra in (b) reveals an improvement of the polarization resistance by a factor of three from 1.5 Ω cm2 to 0.5 Ω cm2 at 600 °C and 97%/3% H2/H2O. The DRT spectra visualize the main impact in the lowest frequency peak allocated to the charge transfer reaction overlapped by minor gas diffusion [1, 3].In this contribution we demonstrate a physicochemically motivated impedance model that enables an optimization of the electrode design of a single-phase fuel electrode in a hydrogen steam operation at different temperatures. In addition to the entire microstructure, the model facilitates a modification of individual microstructural parameters including tortuosity, volume fraction, pore diameter or surface area. Geometrical parameters such as the electrode thickness or electrode area can be adjusted, too.
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