Theoretical insights into H2S reaction mechanism over CuFe2O4 oxygen carrier

Abstract

CuFe2O4 is a promising oxygen carrier because of its high reactivity and good resistance to sintering. The existence of H2S in fuel gas may lead to the poison of oxygen carrier during chemical-looping combustion. The reaction mechanism of H2S over CuFe2O4 was systematically investigated at molecular level based on the periodic slab model and density functional theory calculations. The results show that H2S reaction over CuFe2O4 includes dehydrogenation, H2O production and SO2 formation. The reaction of HS∗ → S∗ + H∗ is the rate-determining step of H2S dehydrogenation. The decomposed H atoms can react with surface O to generate H2O through overcoming an energy barrier of 158.51 kJ/mol. S∗ can be oxidized by surface O to produce SO2, and the energy barrier is 81.15 kJ/mol. The O vacancy produced from H2O desorption can affect the reaction behavior of H2S. The adsorption energies of H2S and its species increase in the presence of O vacancy, while the energy barrier for H2O production decreases to 103.37 kJ/mol. The S atom on the surface migrates and fills the O vacancy.