Mechanistic insights into the reaction behavior of LaMnO3 oxygen carrier material with sulfur species

Perovskite-structured LaMnO 3 has emerged as a potential oxygen carrier material for chemical looping applications because of its remarkable properties. However, the presence of H 2 S in practical chemical looping combustion systems induces sulfur poisoning through surface sulfidation, significantly compromising the performance and durability of oxygen carrier materials. To elucidate the fundamental mechanisms underlying this deactivation process, we performed systematic density functional theory method to investigate the atomic-level interactions between sulfur species (H 2 S, HS and S) and the LaMnO 3 surface. The result shows that the Mn-terminated surface demonstrating better reactivity and thermodynamic stability compared to its La-terminated surface. Thermodynamic analysis confirms the adsorption affinity trend of S > HS > H 2 S upon LaMnO 3 . The elementary step of HS* + * → S* + H* acts as the rate-determining process in H 2 S decomposition, whose activation energy barrier is 0.53 eV. The liberated hydrogen atoms subsequently undergo recombination with surface oxygen species, resulting in the formation of gaseous H 2 O ( E a = 0.80 eV). Notably, the oxidative conversion of adsorbed sulfur species to SO 2 proceeds with significantly lower energy barriers ( E a = 0.80 eV), indicating preferential SO 2 generation compared to H 2 O formation during surface reactions. This reactivity disparity stems from crystallographic-dependent variations in atomic coordination geometry, which substantially influences the electronic structure. • The sulfur-related reactions over the LaMnO 3 0 1 0 surface are explored. • HS* + * → S* + H* is the rate-determining step in H 2 S dissociation over LaMnO 3 surface. • The adsorption intensities of dissociated sulfur species, especially S*, are quite high. • In the CLC with perovskite, the decomposition of H 2 S should be avoided to control sulfur. • Kinetically, it is much easier to form SO 2 than to form H 2 O over the LaMnO 3 surface.