The role of lattice oxygen in deactivation of La0.75Sr0.25Cr0.5Mn0.5O3 +/-delta (LSCM55) as anode catalyst was studied in a solid oxide fuel cell (SOFC), where hydrogen sulfide (H2S) was utilized as fuel. After LSCM55 treated in H2S or H-2-H2S, XRD patterns show that some impurities similar to La2O2S and MnOS are present. XPS spectra identify that S species in the impurities dominate on the anode catalysts in form of sulfate (SO42-), which depends on the treatments. S-2p and O-1s regions in XPS reveal that in the absence of oxygen, lattice oxygen not only on the surface but also in the bulk contributes to the formation of sulfate. Oxygen vacancies induced by H-2 pre-reduction may provide the channel for lattice oxygen migrating from the bulk to the surface. Furthermore, it is found that LSCM55 with H-2 pre-reduction achieves better lifespan of SOFC fueled by H2S than LSCM55 without H-2 pre-reduction, which alleviates deactivation of anode catalyst, due to incomplete oxidation of H2S by residual lattice oxygen on the surface after H-2 pre-reduction. However, improvement of H-2 pre-reduction on anode catalysts LSCM55 is influenced to a certain degree after short-term operation under closed circuit. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.