Preadsorbed SO3 Inhibits Oxygen Atom Activity for Mercury Adsorption on Cu/Mn Doped CeO2(110) Surface

The coadsorption of Hg⁰ and SO₃ on pure and Cu/Mn doped CeO₂(110) surfaces were investigated using the Density Functional Theory (DFT) method. A p (2 × 2) supercell periodic slab model with seven atomic layers was constructed to represent the CeO₂(110) surface. The results indicated that Hg⁰ physically adsorbed on the CeO₂(110) surface, while Hg⁰ chemically adsorbed on the Cu/Mn doped CeO₂(110) surface, which agree well with the experimental results that Cu and Mn doped CeO₂ greatly improved the Hg⁰ adsorption capacity of the adsorbent. The calculated results suggested that SO₃ more easily adsorbs on the above three surfaces than Hg⁰ due to the higher adsorption energy. The adsorption configurations and electronic structures indicated SO₃ reacted with O atoms of the surface to form SO₄²– species. Hence, SO₃ inhibits Hg⁰ adsorption on the CeO₂(110) surface by competing with Hg⁰ for surface lattice oxygen. In addition, SO₃ decreased the activity of the surface O atoms, which directly caused the negative effect on Hg⁰ adsorption.