Influence of SO₂ on the Long-Term Durability of SOFC Cathodes

Abstract

Sulfur poisoning effect on the electrochemical performance and long-term durability of SOFC cathodes has been investigated for (La 0.8 Sr 0.2 ) 0.98 MnO 3 (LSM) and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) up to 1000 hours. Gradual degradation of performance occurred, associated with the formation of strontium sulfate, which depended on SO 2 concentration.

Thermochemical stability of LaxSr1-xCoyFe1-yO3-δ and NiFe2O4-Ce0.8Tb0.2O2-δ under real conditions for its application in oxygen transport membranes for oxyfuel combustion

“…These perovskites easily form carbonates and sulphates (mainly Ba and Sr carbonates/sulphates) or undergo phase segregation [13,16]. This was also observed in several works focused on La0.6Sr0.4Co0.2Fe0.8O3-δ stability when used as SOFC cathodes exposed to CO2 and SO2 [28][29][30], as well as for similar perovskites consisting of La0.6Sr0.4CoO3-δ [31,32]. In addition, the presence of steam in the system affects both the oxygen transport properties and the thermochemical resistance of MIECs [15,[33][34][35].…”

Surface Segregation in Solid Oxide Cell Oxygen Electrodes: Phenomena, Mitigation Strategies and Electrochemical Properties

“…Various volatile impurities exist in SOC stacks, such as gaseous CrO 3 from chromia-forming metallic interconnects and high-temperature alloys used in Balance-of-Plant (BoP) components, SO 2 , CO 2 and H 2 O from airstream and boron species from borosilicate glass sealants. Surface-segregated cations tend to interact actively with these volatile impurities, leading to the deposition of impurities, microstructural changes and operating instability [39,48,49,57,[187][188][189][190][191][192][193][194][195][196][197][198][199][200][201][202][203].…”

“…Sulphur in air streams can significantly affect the performance and durability of SOFCs [191,215,216]. For example, Wang et al [217] studied the mechanism and kinetics of sulphur deposition on LSM electrodes at 700 °C and 800 °C in 1 ppm and 10 ppm SO 2 and reported that the deposition of SO Xiong et al [191] also investigated the sulphur poisoning of LSM electrodes in highly concentrated 0.01% SO 2 in air and reported that the LSM electrode was relatively stable during cathodic polarization at 800 °C for 5 h. On the other hand, Liu et al [190] tested a double-layer oxygen electrode with an LSM-ScSZ inner layer and an LSM outer layer in 20 ppm SO 2 and reported that after cathodic polarization at 800 °C for 1000 h, SrSO 4 particles were observed around the LSM particles in both layers of the electrode. Wang et al [218] further reported that the deposition of sulphur and formation of SrSO 4 were at the LSM/YSZ interface in the presence of 1 ppm SO 2 at 800 °C under anodic polarization conditions and attributed this to the fact that anodic polarization can promote SrO segregation at the LSM close to the YSZ electrolyte, promoting the formation of SrSO 4 and interfacial delamination.…”

“…Compared with LSM, cobaltite oxygen electrodes such as LSC, Sm 0.5 Sr 0.5 CoO 3 (SSC) and LSCF have much higher tendencies to react with SO 2 . For example, Schuler et al [58,219] exposed a double-layer oxygen electrode consisting of a LSM-YSZ inner layer and an LSC outer layer to ~ 12 ppb SO 2 and reported that after operation at 800 °C for 1900 h, SrSO 4 preferentially deposited onto the LSC layer, in which the formation of more SrSO 4 on the cobaltite electrodes as compared with that on LSM electrodes was believed to be due to the higher activity of SrO in cobaltite electrodes [58,190,191]. Here, the reaction between SO 2 and LSC is favourable under oxygen-rich atmospheres and can be described by:…”

Analysis of Thermal Stress in a Solid Oxide Fuel Cell Due to the Sulfur Poisoning Interface of the Electrolyte and Cathode

“…45 The results are in good accordance with the previous experimental results, i.e., the sulfur poisoning deactivates the active cathode and causes deterioration in the microstructure. 9,10,13,20 It also offers a deep understanding of SO 2 poisoning of the LSM cathode and helps to optimize the material composition and morphology to avoid potential mechanical failure and catalytic deactivation.…”