DFT study of the oxidation of Hg⁰ by O₂ on an Mn-doped buckled g-C₃N₄ catalyst

Due to the water-insoluble nature of Hg⁰, its oxidization to Hg²⁺, which is water-soluble, is a viable approach for its effective removal at coal-fired plants using existing flue gas desulfurization (FGD) unit. In this study, the adsorption and oxidation of elemental mercury on an Mn-doped g-C₃N₄ material were investigated. The spin-polarized density functional theory method was adapted to optimize the geometry structures and then to determine the corresponding electronic structures, while the CI-NEB method was adopted to search for the stable intermediates during the reaction(s). The analysis of energy and project density of states shows that the Mn-g-C₃N₄ exhibits an excellent affinity to Hg atoms. It is found that it is feasible for Hg atoms to oxidize on the Mn-g-C₃N₄ surface via two possible E-R paths, but with relatively high energy barriers. This research provides insights into a viable way for mercury removal using O₂ as the oxidizing agent.