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

Abstract

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.