Understanding the Role of Surface Oxygen in Hg Removal on Un-Doped and Mn/Fe-Doped CeO2 (111).

Effects of surface-adsorbed O and lattice O for the CeO2 (111) surface on Hg removal has been researched. In this work, periodic calculations based on density functional theory (DFT) were performed with the on-site Coulomb interaction. Hg is oxidized to HgO via the surface-adsorbed O by overcoming a Gibbs free energy barrier of 114.1 kJ·mol-1 on the CeO2 (111) surface. Mn and Fe doping reduce the activation Gibbs free energy for the Hg oxidation, and energies of 70.7 and 49.6 kJ·mol-1 are needed on Ce0.96 Mn0.04 O2 (111) and Ce0.96 Fe0.04 O2 (111) surfaces. Additionally, lattice O also plays an important role in Hg removal. Hg cannot be oxidized leading to the formation of HgO on the un-doped CeO2 (111) surface owing to the inertness of lattice O, which can be easily oxidized to HgO on Ce0.96 Mn0.04 O2 (111) and Ce0.96 Fe0.04 O2 (111) surfaces. It can be seen that both surface-adsorbed O and lattice O play important roles in removing Hg. The present study will shed light on understanding and developing Hg removal technology on un-doped and Mn/Fe-doped CeO2 (111) catalysts. © 2019 Wiley Periodicals, Inc.