Stabilities and electrical conductivities of electrode materials for use in H2S-containing gases

Stabilities and conductivities of sulfides and lithiated sulfides derived from La_0.9Sr_0.1Ga_0.8Cr_0.2O₃, LaCr_0.9Ti_0.1O₃, Y_0.9Ca_0.1FeO₃, and SrCo_0.8Fe_0.2O₃ are studied in a gas mixture of 96% H₂ and 4% H₂S at 900 °C using X-ray diffraction, microscopy, and impedance spectroscopy. Results indicate that the sulfide and lithiated sulfide derived from Y_0.9Ca_0.1FeO₃ exhibit not only high stability but also high electrical conductivity, implying that they are viable candidate electrode materials for H₂S polishing and for solid oxide fuel cells using H₂S-containing fuels. In contrast, the lithiated sulfides derived from La_0.9Sr_0.1Ga_0.8Cr_0.2O₃ and LaCr_0.9Ti_0.1O₃ exhibit relatively low electrical conductivity, although their chemical and thermal stability appear to be very good. On the other hand, the lithiated sulfides derived from SrCo_0.8Fe_0.2O₃ show inadequate chemical stability under the testing conditions even though the electrical conductivity appears to be good.