Heterogeneous catalytic reaction of NO2 to HONO on hematite

Abstract

The heterogenous catalytic reactions of NO2 on mineral dusts represent one of the important sources of HONO that promote the formation of O3 and other air pollutants, but the mechanism is poorly understood. First principles calculations, including a Hubbard-like +U correction and a dispersion correction, were employed to investigate the heterogeneous interaction of NO2 on the hematite (0001) surface. The competitive adsorption between the most common gas molecules in polluted air (NO2, CO, SO2, O3, H2O, O2, and N2) were also investigated. Under dry conditions, the (NO3δ−)(NOδ+) intermediate species can transform into surface NO3 and gaseous NO. Under wet conditions, the simulations predicted the production of HONO and HNO3 through the hydrolysis of NO2 via (NO3δ−)(NOδ+). Adsorption energies show that the surface Fe site provides strong interactions. Charge transfer occurs from the Fe atom to the adsorbate molecules. This study may facilitate the understanding of the transformations of the atmospheric gas pollutants on naturally occurring mineral dust aerosols. The heterogenous reaction may impact on global atmospheric chemistry.