DFT study of mercury adsorption on α-Fe2O3 surface: Role of oxygen

First-principle calculations based on density functional theory were performed to investigate the micro-mechanism of Hg0 adsorption on α-Fe2O3 (0 0 1) surface in the presence of O2. Considering O2 is more easily adsorbed on α-Fe2O3 than Hg0, this paper investigated Hg0 adsorption on O2 embedded α-Fe2O3 (0 0 1) surface to clarify the effect of O2 on the capture of mercury by α-Fe2O3. Theoretical calculations indicate that O2 dissociates in two steps on the surface, leaving one O atom to interact with a surface Fe atom. Hg0 adsorption on O/α-Fe2O3 (0 0 1) surface belongs to weak chemisorption, and the potential energy diagram is provided. Additionally, the study of coverage shows that O atom coverage has a huge impact on Hg0 adsorption. The adsorption mechanism of Hg0 on the surface changes from weak chemisorption into stronger chemisorption as the O coverage increases from 0.25 to 1 mL, with the largest adsorption energy of −268.1 kJ/mol.