Complete catalytic reaction of mercury oxidation on CeO/TiO (001) surface: A DFT study.

CeO/TiO catalyst is a promising material for realizing the integration of denitrification and mercury removal to reduce mercury emissions. Oxidation mechanism of Hg on CeO/TiO (001) surface in the presence of HCl and O was studied by density functional theory (DFT). The results indicated that Hg was physically adsorbed on CeO/TiO (001) surface. As an important intermediate, HgCl was adsorbed on the surface of CeO/TiO (001) utilizing enhanced chemisorption, while the adsorption energy of HgCl was only -57.05 kJ/mol. In the absence of HCl, mercury oxidation followed the Mars-Maessen mechanism with a relatively high energy barrier, and the product (HgO) was difficult to desorb, which hindered the reaction process. When HCl existed, reactive chlorine (Cl*) would be produced by the dissociation of HCl, and the mercury oxidation would follow the Langmuir-Hinshelwood mechanism. The co-existence of HCl and O had no significant effect on the adsorption of Hg, but reduced the reaction energy barrier and the final product (HgCl) was more easily desorbed from the catalyst surface. In addition, two complete cyclic reaction pathways for catalytic oxidation of Hg on CeO/TiO (001) surface were constructed to clarify the detailed reaction process.