Density Functional Theory Study of the Effects of NH3 and NO2 on Hg0 Oxidation over V2O5/TiO2 Under Fast Selective Catalytic Reduction Conditions

The effects of NO2 and NH3 on Hg0 oxidation under fast selective catalytic reduction conditions remain unclear. To address this problem, we performed density functional theory calculations on the V2O5/TiO2(001) surface in four states: clean surface, surface covered by NH3, surface covered by NO2, and surface where species are co-adsorbed. On the clean surface, Hg0 interacts weakly with oxygen sites; the adsorption energies at terminal (Ot), bridging (Ob) and interfacial bridging (Ob′) oxygen sites are −12.31, −12.58, and −21.22 kcal mol−1, respectively. Direct oxidation by lattice oxygen encounters high activation barriers, ranging from 146.817 to 184.529 kcal mol−1. NH3 hinders the capture of Hg0. Since NH3 preferentially occupies the vanadium-related active sites, the interaction between Hg0 and the catalyst is weakened, and the adsorption energies become less negative, ranging from −11.84 to −11.04 kcal mol−1. NO2 shows the opposite effect. It strengthens Hg0 adsorption near V-centered regions and provides an alternative oxygen source for Hg0 oxidation. The NO2-assisted oxygen-transfer pathways have lower calculated barriers, ranging from 74.581 to 108.545 kcal mol−1. When NH3 and NO2 are co-adsorbed, the barrier increases to 113.326 kcal mol−1. Even so, NO2-derived oxygen provides a relatively lower-energy oxygen-transfer route than lattice oxygen among the pathways examined.