Adsorption of NO and O2 on MnO2 and (MnO2)3/Al2O3

Abstract

Based on first-principles density functional theory (DFT), the adsorption performance of MnO2(110) surface for NO and O2 was calculated, and the deposition of (MnO2)3cluster on the γ-Al2O3(110) surface was studied. In addition, the adsorption and co-adsorption of NO and O2 on the surface of (MnO2)3/Al2O3 were further calculated. The results showed that NO was more inclined to adsorb on the four-coordinated Mn(Ⅳ) sites on the MnO2(110) surface (the maximum Eads was −75.35KJ·mol−1). There were very few O2 adsorption sites on the MnO2(110) surface, and only the vacancies between adjacent Mn(IV) could adsorb O2 stably. PDOS analysis showed that the hybridization between Mn 3d orbital and N 2p (or O 2p) orbital was the main reason for Mn-N bonds (or Mn-O bonds). The (MnO2)3 cluster tended to load on Al2O3(110) surface in a flat six-membered ring structure. There are abundant active oxygen sites on the (MnO2)3/Al2O3 surface, which had an excellent ability to adsorb NO (the maximum Eads was −278.24 KJ·mol−1). NO molecules interacted with surface-active oxygen to generate nitroso, and NO2 was easily desorbed from the (MnO2)3/Al2O3 surface. The co-adsorption of NO and O2 on the (MnO2)3/Al2O3 surface formed an ONOO* structure, which could decompose to form adsorbed NO2* and O*. Compared with single-phase manganese oxide crystals, manganese oxide clustered on γ-Al2O3 had superior NO adsorption performance and may have excellent catalytic oxidation properties.