Heterogeneous oxidation mechanism of SO2 on α-Fe2O3 (001) catalyst by HONO: Effect of oxygen defect

To investigate the heterogeneous oxidation mechanisms of SO2 by HONO on the alpha-Fe2O3 surfaces, the individual and combined adsorption characteristics of SO2 and HONO on the perfect and O-defect alpha-Fe2O3 (001) surfaces were calculated the density functional theory. Results revealed that SO2 was molecularly adsorbed while HONO was dissociated on prefect and O-defect surfaces. Oxygen defect significantly augmented the adsorption intensities of SO2 and HONO and accelerated decomposition (HONO ->center dot OH + NO) of HONO. Analysis of electronic structures demonstrated demonstrated that the decomposition of HONO followed the Haber-Weiss mechanism. HOSO2 was generated (SO2 + center dot OH -> HOSO2) on the prefect and O-defect surfaces through SO2 and HONO co-adsorption, thereby confirming that SO2 was oxidized. Moreover, the low energy barrier of HONO decomposition (prefect: 90.67 kJ/mol; O-defect: 50.20 kJ/mol) and SO2 oxidation (prefect: 46.90 kJ/mol; O-defect: 31.09 kJ/mol) suggested that SO2 was easily oxidized by HONO on the alpha-Fe2O3 (001) surface.

Automated summary

In this study, the adsorption characteristics and reaction mechanisms of SO2 and HONO on the α-Fe2O3 surface were investigated using density functional theory. The results showed that SO2 adsorbs as a molecule, while HONO dissociates on the surface. The presence of oxygen defects enhanced the adsorption intensity of both molecules and accelerated the decomposition of HONO, leading to the oxidation of SO2 by HONO.