Mechanism insights into elemental mercury oxidation on RuO2(110) surface: A density functional study

Periodic DFT computational studies are applied to investigate mercury adsorption and oxidation mechanism over RuO2 catalyst. The adsorption of mercury species (Hg-0, HgCl, HgCl2) and HCl on RuO2(1 1 0) surface were obtained. The results indicate that all the mercury species have strong interaction with RuO2(1 1 0) surface and the unsaturated Ru sites have best ability for adsorption mechanism. HCl prefers to dissociate on the surface with adsorption energy of -238.00 kJ/mol, leading to a hydroxyl group and ruthenium-chlorine complex. After water desorption from the surface, different chlorinated surface has been formed at various oxygen coverage. The Hg oxidation reaction follows the Langmuir-Hinshelwood mechanisms in which both Hg and Cl are adsorbed before reacting with each other. Furthermore, reaction pathways of mercury oxidation on different chlorinated surfaces are examined and the activation barriers are 194.22 kJ/mol and 90.94 kJ/mol, respectively. These results revealed that precovered oxygen on the surface is more active than lattice oxygen, which can improve HCl dissociation and Hg oxidation. Our approach provides new insights into the role of O-2 during Hg oxidation process.