Suppressed lattice oxygen mobility on Ag/FeO_x catalyst enhances the sulfur selectivity of H₂S selective oxidation

The regulation of lattice oxygen mobility on metal oxide-based catalysts holds great significance for balancing the conversion and selectivity in the selective catalytic oxidation of H₂S (H₂S-SCO). Herein, we successfully suppress the lattice oxygen mobility of iron oxide-based catalyst via Ag loading to realize the high H₂S removal effect and high sulfur selectivity simultaneously. The Ag-loaded FeO_x catalyst synthesized by simple precipitation and impregnation method exhibits an outstanding sulfur capacity of 3344.9 mgS g_cat^-1 and a high sulfur selectivity of 93.0 % at 120 °C, which is superior to those of FeO_x catalyst (771.1 mgS g_cat^-1 and 86.4 %). The X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) and hydrogen temperature programmed reduction (H₂-TPR) characterization results reveal that the bond energy of Fe-O is enhanced via Ag loading, resulting in the reduced lattice oxygen mobility. Furthermore, oxygen temperature programmed desorption (O₂-TPD) result shows that the amount of lattice oxygen is decreased after Ag loading. These regulations of lattice oxygen prevent the over-oxidation of H₂S and improve sulfur selectivity, thereby delaying the catalyst poisoning and prolonging the lifespan of catalyst. Meanwhile, the Ag loading reduces the alkaline environment on the catalyst surface, which avoids the accumulation of sulfur. This work provides a new insight into designing desulfurizers with high conversion and selectivity for H₂S-SCO process.