Density Functional Theory Study of Elemental Mercury Adsorption on Fe2O3[104] and Its Effect on Carbon Deposit during Chemical Looping Combustion

This study investigated the adsorption of elemental mercury (Hg0) on perfect and reduced Fe2O3[104] surfaces as well as analyzed the synergistic effect of Hg0 on the catalytic decomposition of CO on the reduced surfaces using density functional theory calculations. This study aimed to clarify the correlations among Hg0 adsorption, CO decomposition, and Fe2O3 reduction degree. Theoretical results indicated that Hg0 underwent Fe top site adsorption to Fe bridge site adsorption as Fe2O3 was reduced into iron. This phenomenon increased Eads with a local extreme of −2.063 eV for Hg0–Fe2O1.364. The adsorption of Hg0 decreased Eads for CO adsorption on the reduced Fe2O3 surfaces but promoted charge transfer from the surface to the adsorbed CO molecule. This event activated the C–O bond, favoring its decomposition. A kinetic model for catalytic CO decompositions with and without Hg0 further revealed the synergistic effect of Hg0 on carbon deposition and the relationship between the reaction rate and degree of chemical looping combustion.