Complete catalytic reaction of mercury oxidation on CeO2/TiO2 (001) surface: A DFT study.

CeO 2 /TiO 2 catalyst is a promising material for realizing the integration of denitrification and mercury removal to reduce mercury emissions. Oxidation mechanism of Hg0 on CeO 2 /TiO 2 (001) surface in the presence of HCl and O 2 was studied by density functional theory (DFT). The results indicated that Hg0 was physically adsorbed on CeO 2 /TiO 2 (001) surface. As an important intermediate, HgCl was adsorbed on the surface of CeO 2 /TiO 2 (001) utilizing enhanced chemisorption, while the adsorption energy of HgCl 2 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 2 had no significant effect on the adsorption of Hg0, but reduced the reaction energy barrier and the final product (HgCl 2) was more easily desorbed from the catalyst surface. In addition, two complete cyclic reaction pathways for catalytic oxidation of Hg0 on CeO 2 /TiO 2 (001) surface were constructed to clarify the detailed reaction process. [Display omitted] • Hg0 oxidation mechanism on CeO 2 /TiO 2 (001) surface was studied by DFT calculation. • Difficult formation and desorption of HgO result in low oxidation efficiency. • HCl and O 2 could significantly reduce the reaction energy barrier. • Hg0 oxidation by HCl followed Langmuir-Hinshelwood mechanism. • Two complete catalytic cycles were constructed to understand the reaction pathway. [ABSTRACT FROM AUTHOR]