Mechanism of Hg⁰ and O₂ Interaction on the IrO₂ (110) Surface: A Density Functional Theory Study

Efficient and effective control of airborne Hg⁰ emission during fossil fuels utilization is one of many challenges. The catalytic oxidation of Hg⁰ to Hg²⁺ is a promising approach for mercury removal as it enables mercury capture at existing air pollution control devices. In this study, IrO₂ was studied in detail based on density functional theory to show the interactions between Hg⁰ and O₂ on the IrO₂ (110) surface. On the basis of the full optimizations of the IrO₂ (110) surface, five stable Hg adsorption configurations have been identified, among which the most stable adsorption position was found to be at the top of a 5-fold coordinated Ir atom (Ircᵤₛ₋ₜₒₚ). Furthermore, in-depth analysis of the interactions between the Hg atom and O atom on the IrO₂ (110) surface showed that the adsorption energy of O is higher than that of Hg⁰ on the Ircᵤₛ₋ₜₒₚ. Moreover, the results suggest that the preadsorption of O atoms has a positive effect on the adoption of Hg, while the adsorption was identified as a chemisorption. More importantly, the Langmuir–Hinshelwood mechanism was determined to be the most probable reaction mechanism. This study provides insight into the prediction of the potential Hg⁰ catalytic oxidation by O₂ on the IrO₂ (110) surface.