Charge-distribution modulation of copper ferrite spinel-type catalysts for highly efficient Hg0 oxidation

Abstract

Hg0 catalytic oxidation is an attractive approach to reduce mercury emissions from industrial activities. However, the rational design of highly active catalysts remains a significant challenge. Herein, the charge distribution modulation strategy was proposed to design novel catalysts: copper ferrite spinel-type catalysts were developed by introducing Cu2+ cations into octahedral sites to form electron-transfer environment. The synthesized catalysts with spinel-type stoichiometry showed superior catalytic performance, and achieved > 90 % Hg0 oxidation efficiency in a wide operation temperature window of 150−300 °C. The superior catalytic performance was closely associated with the mobile-electron environment of copper ferrite. Hg0 oxidation by HCl over copper ferrite followed the Eley-Rideal mechanism, in which physically adsorbed Hg0 reacted with active chlorine species. Density functional theory calculations revealed that octahedral Cu atom is the most active site of Hg0 adsorption on copper ferrite surface. Both direct oxidation pathway (Hg* → HgCl2*) and HgCl-mediated oxidation pathway (Hg* → HgCl* → HgCl2*) played important role in Hg0 oxidation over copper ferrite. HgCl2* formation was identified as the rate-limiting step of Hg0 oxidation. This work would provide a new perspective for the development of admirable catalysts with outstanding Hg0 oxidation performance.