Highly efficient nanosized Mn and Fe codoped ceria-based solid solutions for elemental mercury removal at low flue gas temperatures

Ceria (CeO2) is a well-known material for various industrial applications due to its unique redox properties. Such properties, dominated by structural defects that are primarily oxygen vacancies associated with the Ce3+/Ce4+ redox couple, can be easily modulated and optimized by different approaches. In this paper, nanosized Mn and Fe codoped CeO2 solid solutions, Ce0.7-xMn0.3FexO2-δ (x = 0.05-0.2), were prepared by a simple coprecipitation method and tested towards elemental mercury (Hg0) oxidation and adsorption. The obtained solid solutions were characterized in detail at the structural and electronic level by various techniques, namely, XRD, ICP-OES, BET surface area, TEM, Raman, H2-TPR, and XPS. The XRD results suggest that the Mn and/or Fe dopant cations are effectively incorporated into the CeO2 lattice. BET surface area results suggest that the addition of Mn and/or Fe dopants to CeO2 significantly reduces its crystallite size and thereby improves the surface area. Raman, H2-TPR, and XPS results reveal that the Mn and/or Fe dopant cations in the ceria lattice increased the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce4+/Ce3+. The Hg0 oxidation and adsorption studies indicate that Ce0.7-xMn0.3FexO2-δ solid solutions exhibited the highest activity compared to pure CeO2. In particular, the Ce0.5Mn0.3Fe0.2O2-δ (CMF20) solid solution shows an Hg0 oxidation efficiency (Eoxi) of 86.5%. It was found that the doping of both Mn and Fe led to lattice distortion and restrained growth of CeO2, resulting in synergistic increase in oxygen vacancies and catalytic activity.