Understanding competitive adsorption of SF6 and its decomposed components on α-Fe2O3

Abstract

Airborne mineral dusts make a big contribution to atmospheric particulate matter, and they can provide reactive surfaces to promote heterogeneous reactions. Atmospheric sulfur hexafluoride (SF6) and its decomposed products are unique pollutants, but little is known about the heterogeneous fate of these gas molecules. This paper presents a preliminary study of the competitive adsorption of SF6 and its decomposed components (SF2O2, SF2O, SO2, H2S, HF) on one of the most common atmospheric mineral surfaces (α-Fe2O3). First-principles calculations were carried out to examine the adsorption mechanism of SF6 and its decomposed gases on the α-Fe2O3(0001) surface, and analyzed in terms of the corresponding adsorption energy, geometrical structure, and charge transfer. It is found that these gas molecules are adsorbed on the α-Fe2O3(0001) mineral surface by chemisorption except SF6. By comparing the adsorption parameters of the six gas molecules, it can be inferred that the adsorption strength of the α-Fe2O3(0001) mineral surface to gases is H2S > HF > SO2 > SF2O > SF2O2 >> SF6. Meanwhile, a competitive adsorption study was also carried out in clean air (N2, O2, H2O). The pollutants (SO2, H2S, HF) would be more easily adsorbed on the α-Fe2O3 surface. This study reveals the nature of the first step (adsorption) of the atmospheric heterogenous reaction at the molecular electronic level, and helps to understand the mechanism of pollution.