Oxygen reaction on strontium-doped lanthanum cobaltite dense electrodes at intermediate temperatures

AC Impedance Characterisation of a La0.8Sr0.2Co0.2Fe0.8O3–δ Electrode

“…Gerischer-like impedance arcs were observed in the present work in the Nyquist plots, clearly for the highest P O 2 and lowest temperatures ( Figure 5), where bulk vacancy concentration becomes the smallest. In view of the fact that the response of a Gerischer element can be approximated over a (Figure 8c) is based on a small number of experimental points, it indicates a gas-phase diffusion limiting step, as in this case a linear dependence of the polarisation conductance on P O 2 is expected [1,5,31,35]. A P 1:42 O 2 dependence has been reported for the polarisation conductance related to the low frequency part of impedance spectra obtained above 700°C with a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d electrode interfaced to CGO [1].…”

“…The high frequency arc can be related to ionic diffusion in the electrode on the basis of the weak dependence (Figure 8a) of R À1 p;HF on P O 2 [5,15,29], assuming that by decreasing P O 2 from 100 to 0.7 kPa the mixed conducting electrode oxygen deficiency and, thus, the concentration of oxygen vacancies carrying the oxide ion current does not increase significantly [30,31]. The average activation energy value of 1.57 eV corresponding to the high frequency step is in reasonable agreement with the activation energy value of ∼1.9 eV reported for oxygen self-diffusion in La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d [7,32], in view of the difference in composition.…”

In Situ TEM Analysis of a Symmetric Solid Oxide Cell in Oxygen and Vacuum – Cation Diffusion Observations

“…It is well known that LSC and YSZ forms insulating second phase compounds such as SrZrO 3 or La 2 ZrO 7 during the usually applied sintering process at high temperatures (above 900 o C) in air, these are insulating phases (21)(22). In our symmetric model cell, the PLD preparation was carried out at 500 o C, and therefore no second phase should be formed.…”

Nanostructured LnBaCo2O6−𝜹 (Ln = Sm, Gd) with layered structure for intermediate temperature solid oxide fuel cell cathodes

“…30 For almost all cathodes, the adjustment of R W yielded a value of n of 0.11 to 0.14 (Table S-II of the supplementary material), which is compatible with bulk diffusion of oxide ions. The only exception is GBCO2 in which n is 0.24, suggesting a limiting step of oxygen exchange redox reaction on the electrode surface between the adsorbed oxygen and the bulk electrode material.…”

“…The only exception is GBCO2 in which n is 0.24, suggesting a limiting step of oxygen exchange redox reaction on the electrode surface between the adsorbed oxygen and the bulk electrode material. 30 From the analysis of R 1 (Table S-III of the supplementary material) of SBCO2, SBCO8 and GBCO8, we obtained n between 0.57 and 0.67, indicating a complex mechanism with an intermediate value between 0.5 (characterizing a dissociative adsorption-limitingstep) and 1 (indicating a gas-phase diffusion-limiting step), while for GBCO2 the value of 1.02 clearly shows that this component mainly arises from gas-phase diffusionthrough the cathode pores. 30 The values of the resistive parts of the equivalent circuit obtained by fitting the data at 700 • C, are presented in Table II (we present the and GbBaCo 2 O 6-δ by a very simple procedure and attached to an electrolyte retaining its original nanostructured character.…”