DFT Study On The Adsorption And Decomposition Of SO₂ And NO₂ On Metal Surface

In this paper,the adsorption of SO2 on Ni surface, the adsorption and decomposition of NO2 on Rh surface are investigated, respectively, by means of the density functional theory(DFT). The adsorption structures and decomposition mechanisms are discussed in detail by the analysis of adsorption energy,bond length, density of states and transition state.1. DFT Study on the Decomposing Adsorption of SO2 on Ni(111) SurfaceThe geometries and properties of SO2 and its fragments adsorption on Ni(111) surface were systematically investigated by means of density functional theory (DFT). The result indicates that SO2 is parallel to Ni(111) surface and its atoms are on the top site of Ni atoms, SO3 adsorbs on Ni(111) surface with its C3v axis declining to the surface. The adsorption geometries of SO have two possible structures, one is SO parallel to the surface, another is SO perpendicular to surface with S atom absorbing to Ni surface. S atom is apt to adsorb on the hollow site. It can also be concluded from the Analysis of the partial density of states and shifting of electrons that the electrons transfer from Ni atoms to SOX, which results in the variation of the electrons locations of S—O bonds and the elongation of S—O bond. The p orbitals of Ni atom donates electrons to S atom in the adsorption of S atom on Ni(111) surface, it is different from the adsorption of 0 atom on Ni(111) surface.2. Theoretical Understanding of the Decomposition Adsorption of NO2 on Rh(111) SurfaceThe adsorption and decomposition mechanism of NO2 and its fragments on Rh(111) surface were systematically investigated by means of density functional theory (DFT). The adsorption of both NO2 on top site and NO on hollow site (fcc and hcp) is favorable on clean Rh(111) surface, while the adsorption of N and O atoms on hollow (fcc) site is preferred. The N—O bond is elongated when adsorbed on Rh(111), which results in the activation of NOx. The decomposition barriers of NO2 and NO decrease markedly when Rh act as catalyst. The presence of Nads and Oads inhibits the dissociation of NOx because of the occupying of N and 0 on the hollow sites of Rh(111). The catabolite of Nads and Oads desorb as N2 and O2 with temperature increase, so the decomposition of NOx could continue to proceed.