Effect of WO 3 doping on the mechanism of mercury oxidation by HCl over V 2 O 5 /TiO 2 (001) surface: Periodic density functional theory study

Commercial vanadium-titanium-based selective catalytic reduction (SCR) catalyst exhibits a certain ability for mercury removal during the denitrification process of coal-fired flue gas. WO 3 is an important additive agent for SCR catalyst, yet few studies have been reported on the role of WO 3 during mercury oxidation process. In this study, periodic V 2 O 5 /TiO 2 and V 2 O 5 -WO 3 /TiO 2 slab models were constructed. Density functional theory (DFT) calculations were applied to explore the effects of WO 3 on the mercury removal mechanism over the SCR catalyst. The effects of WO 3 doping on the electronic structure of the catalyst were investigated. The adsorption configurations and energies of mercury species before and after WO 3 doping were calculated. The reaction pathways and energy barriers of mercury oxidation were further analyzed. The results indicate that WO 3 promotes the charge transfer on the catalyst surface and enhances the reaction activity. The adsorption energies of Hg and HgCl on the catalyst surface decrease after WO 3 doping, while the adsorption energies of HgCl 2 increase. Additionally, WO 3 doping reduces the energy barrier of mercury oxidation, thus enhancing the mercury removal capacity of the SCR catalyst. The oxidation process of mercury over the vanadium-titanium-based SCR catalyst follows the Langmuir-Hinshelwood mechanism, which is different from previous theoretical results.