Long-Term Study of MIEC Cathodes for Intermediate Temperature Solid Oxide Fuel Cells

Abstract

The time-related change of anode supported single cell performance for intermediate temperature SOFC was evaluated continuously up to 700 hours of operation. For the first time, cathodic and anodic polarization losses were separated by high resolution impedance studies based on DRT analysis (distribution of relaxation times) followed by a CNLS fitting approach. The cathodic polarization resistance (15mΩcm2 at t = 11 h), by far the smallest part, could only be visualized in the relevant frequency range by well selected and adapted experimental parameters. Within 700h the cathode resistance increases by 400% (63mΩcm2 at t = 700 h) undergoing a nonlinear degradation rate which can not explained by microstructural changes but probably by compositional changes.

Characterisation of La0.6Sr0.4Co0.2Fe0.8O3-δ – Ba0.5Sr0.5Co0.8Fe0.2O3-δ composite as cathode for solid oxide fuel cells

“…6 presents the RP trend for composite and BSCF cathode during an ageing test of 200 hours. The exposure time is in accordance with several literature works, that identified a period between 100-300 h as acceptable for a preliminary ageing test [53][54][55][56]. After 200 h composite cathode increased polarization resistance of about 5 %, which represents an important improvement if compared with the 38 % of degradation shown by BSCF under the same operation condition.…”

Impedance Study of Alternative (La,Sr)FeO[sub 3−δ] and (La,Sr)(Co,Fe)O[sub 3−δ] MIEC Cathode Compositions

“…Based on this value range, a set of mean values was defined ͑see the fourth row of Table IV͒, which was used to calculate the D ␦ and k ␦ values from R 2C and t 2C , thereby making the simplifying assumption of temperature and oxygen partial pressure independent ␥, ␦, and c mc values. diagrams, the data of Endler et al 1 obtained on L58SCF at 750°C before and after long-term measurements are included. Both coefficients ͑k ␦ and D ␦ ͒ of the cathodes analyzed within this study show an Arrhenius behavior and thus can be approximated very well with a straight line.…”

“…Recently, a long-term study on state-of-the-art ASCs from Forschungszentrum Jülich ͑FZJ͒ with a high performance La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3−␦ cathode ͑L58SCF͒ showed an increase in the polarization resistance at 750°C by 310% ͑from 0.015 to 0.062 ⍀ cm 2 ͒ within 700 h. 1 This result gives evidence for the need of alternative candidate compositions. In this study, two cathodes, La 0.68 Sr 0.3 FeO 3−␦ ͑LSF͒ and La 0.68 Sr 0.3 Co 0.2 Fe 0.8 O 3−␦ ͑L68SCF: La-rich͒, which are characterized by electrochemical impedance spectroscopy ͑EIS͒ over a wide range of operating conditions, are introduced.…”

Limiting factors for planar solid oxide fuel cells under different trace compound concentrations

“…The design of SOFC supported anodes has been extensively investigated over the last few years because of their relatively easy of manufacturing and potentially high power density. Moreover, the cathode material of LSCFs has been investigated for intermediate temperature SOFC applications [23,[28][29][30][31][32][33] and a polarization resistance of 0.018 Ωcm 2 has been shown at 750 °C as well as relative stability (400% of increased polarization resistance in 700 h) [34].…”