DFT and Experimental Study on the Mechanism of Elemental Mercury Capture in the Presence of HCl on α-Fe_2O_3(001)

摘要

To investigate the mechanism of Hg~0 adsorption on the α-Fe_2O_3(00l) surface in the presence of HCl, which is considered to be beneficial for Hg~0 removal, theoretical calculations based on density functional theory as well as corresponding experiments are carried out. HCl adsorption is first performed on the α-Fe_2O_3(00l) surface, and the Hg~0 adsorption on HCl-adsorbed α-Fe_2O_3(001) surface is subsequently researched, demonstrating that HCl dissociates on the surface of α-Fe_2O_3, improving the Hg~0 adsorption reactivity. With further chlorination of the α-Fe_2O_3(001) surface, FeCl_3 can be achieved and the adsorption energy of Hg~0 on the FeCl_3 surface reaches -104.2 kJ/mol, representing strong chemisorption. Meanwhile, a group of designed experiments, including Hg~0 adsorption on HCl-preadsorbed α-Fe_2O_3 as well as the coadsorption of both gaseous components, are respectively performed to explore the pathways of Hg~0 transformation. Combining computational and experimental results together, the Eley-Rideal mechanism with HCl preadsorption can be determined. In addition, subsequent X-ray photoelectron spectroscopy analysis verifies the appearance of Cl species and oxidized mercury, exhibiting the consistency with experiments.