Pinning-down polarization losses and electrode kinetics in cermet-supported LSM solid oxide cells in reversible operation

Application of a General Gas Electrode Model to Ni-YSZ Symmetric Cells: Humidity and Current Collector Effects

“…In recent reports 11,12) by the present authors' group, unlike in other reports, [13][14][15][16] a simplified ideal three-parameter Bisquert model, as shown in Fig. 1(b), has been successfully applied.…”

“…Recently, the classical electrochemical model for a porous electrode in liquid electrolyte has been successfully applied to the Ni-YSZ and LSM-YSZ gas electrode reactions, in full Ni-YSZ/YSZ/LSM-YSZ solid oxide cells. [10][11][12] The classical electrode impedance in solution can be modeled as the transmission line in Fig. 1(a), with impedance (1) where l is the thickness of the electrode layer and λ =…”

“…The distributed elements χ 1 and χ 2 (or χ 2 and χ 1 ) represent the impedance of the liquid paths and of the solid network, respectively; ζ represents the impedance of the solid/liquid interface. The model is available for fitting and simulation in a commercial program, Zview, as a Bisquert model (DX-11), notated as 'B,' in the previous work, 11,12) where χ 1 , χ 2 , and ζ are each a parallel combination of a resistor R and a CPE (constant phase element) with complex capacitance Q* = A(jω) α-1 . The model was probably first applied by Sonn et al 13) to describe the electrochemical impedance on symmetrical cells with Ni-YSZ gas electrodes.…”

“…12) Similarly, the model has been applied to symmetrical cells with LSM-ScYSZ, 15) -CGO or -Ag-CGO electrodes, 16) and LSM-YSZ electrodes in full solid oxide cells. [10][11][12] The electrochemical behavior of LSM, essentially an electronic conductor, is comparable to that of Pt or Ni rather than to that of -------------l 2λ sinh l/λ ( ) ------------------------+ λ χ…”

“…While the electrochemical impedance of Ni-YSZ electrodes in full solid oxide cells is often small compared to the other impedance components, and is severely affected by high frequency stray effects, the gas concentration impedance originating from Ni-YSZ cermet support in the low frequency region has been shown to be the major loss component for the low-humidity high-temperature operation of solid oxide cells. 10,11) Fig. 1(c) shows a simulated response of the hydrogen electrode based on the full cell results.…”