Co-regulation of dispersion, exposure and defect sites on CeO₂ (111) surface for catalytic oxidation of Hg⁰

The additional cost of Hg⁰ capture in coal-fired power plants has facilitated the demand for environmental pollutants mitigation material for Hg⁰ oxidation to Hg²⁺ for an ultra-low Hg emission technology. Herein, a suite of CeO₂-based catalysts were investigated aiming at ultra-low gaseous Hg⁰ emission at coal-fired power stations. Gaseous elemental mercury is feasible to be catalytically oxidized to Hg²⁺. The co-regulated dispersion, exposure and defect sites on CeO₂ (111) surface with 2 wt% Ce and 8 wt% Mo compositions on γ-Al₂O₃ was found to be the most promising catalyst demonstrating a high catalytic oxidation efficiency, a broad operating temperature range and a low activation energy. Specifically, it is shown that the oxidation of Hg⁰ on the Ce-based catalysts can be enhanced by the addition of Mo (up to 8 wt%) via promoting the CeO₂ (111) surface dispersion and exposure. Moreover, insights into the Ce and Mo synergistic interactions showed that it facilitated the formation of defect-containing surface sites. Besides, the co-regulation of dispersion, exposure and defect sites on CeO₂ (111) surface was further studied by DFT calculations. This study provides a feasible approach in optimization of CeO₂-based catalysts for catalytic oxidation of Hg⁰ to achieve efficient removal of environmental pollutants.