Theoretical prediction of graphene-based single-atom iron as a novel catalyst for catalytic oxidation of Hg0 by O2

Rapid and high efficient catalytic oxidation of elemental mercury (Hg-0) to oxidized mercury (Hg2+) is a key step to remove mercury pollution from coal-fired power plants. Here, we applied four kinds of graphene-based single-atom iron catalysts (FeSA/GS) for catalytic oxidation of Hg-0 by O-2 to determine the reaction mechanisms via analysis of final products, reaction path, dominant mechanism and catalytic activity based on density functional theory (DFT) calculations. The results reveal that the final product for catalytic oxidation of Hg-0 by O-2 is the chain (HgO)(2) cluster and its desorption process of the chain (HgO)(2) cluster is the rate-determining step. Among the four kinds of FeSA/GS investigated, the single-atom iron catalyst supported with double vacancy doped four N atoms graphene-based substrate has the highest catalytic activity with energy barrier of the rate-determining step at 2.34 eV. The adsorption energy of O-2 has an obviously positive proportional relationship with the energy barrier of the rate-determining step. The stability of catalyst is analyzed through relative binding energy and ab inito molecular dynamics simulation. This theoretical work is the first to explore graphene-based single-atom catalysts for catalytic oxidation of Hg-0 by O-2 in flue gas, and proves the feasibility of single-atom catalysts for the catalytic oxidation of Hg-0.