MoO₃-adjusted δ-MnO₂ nanosheet for catalytic oxidation of Hg⁰ to Hg²⁺

The challenge of Hg⁰ emission control has necessitated the development of catalytic oxidation technology. Herein, a combination of experimental and computational approach to explore the potential over Mo-Mn catalysts was conducted. Series of catalysts were synthesized and characterized with varying Mn and Mo loading (1–10%). Among the various compositions, 1.25Mo2 Mn catalyst exhibited the best Hg⁰ removal performance with Hg⁰ removal efficiency > 98% (oxidation ratio > 50%, and better stability over 10 h period at 250 °C). Most importantly, the synergistic interaction between MoO₃ and defective δ-MnO₂ nanosheet was promoted by the adjusted activation energy, bond strength, Brønsted acidic sites and defects, which facilitated the catalytic oxidation of Hg⁰ to Hg²⁺. Furthermore, DFT calculations suggested that the role of Mo enabled the reduction in the energy barrier for the desorption step, which was defined as the rate-determining step for catalytic oxidation of Hg⁰ on Mn-based catalyst.