Sulfur poisoning mechanism of LSCF cathode material in the presence of SO₂: a computational and experimental study

Abstract

Aiming at the comprehensive understanding of the single sulfur poisoning effect and, eventually, the multiple impurities poisoning phenomena on the SOFC (Solid Oxide Fuel Cell) cathode materials, the sulfur poisoning effect on the (La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O₃ (LSCF-6428) has been investigated in the presence of 10 ppm SO₂ at 800, 900, and 1,000 °C, respectively, with a combined computational and experimental approach. The good agreement between the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) simulations and the XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), and TEM (Transmission Electron Microscopy) characterization results support the reliability of the CALPHAD approach in the SOFC field. Furthermore, comprehensive simulations were made to understand the impact of temperature, P(SO₂), P(O₂), and Sr concentration on the threshold of SrSO₄ stability. Results showed that the formation of SrSO₄ is thermodynamically favored at lower temperatures, higher P(SO₂), higher P(O₂), and higher Sr concentration. Finally, comparisons were also made between LSCF-6428 and LSM20 (La_0.8Sr_0.2MnO₃) using simulations, which confirmed that LSCF-6428 is a poor sulfur-tolerant cathode, in agreement with the literature.

Keywords

LSCF cathode / CALPHAD / sulfur poisoning / long-term degradation / accelerated testing

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