Constructing Heterointerfaces in Dual-Phase High-Entropy Oxides to Boost O₂ Activation and SO₂ Resistance for Mercury Removal in Flue Gas

The low O₂ activation ability at low temperatures and SO₂ poisoning are challenges for metal oxide catalysts in the application of Hg⁰ removal in flue gas. A novel high-entropy fluorite oxide (MgAlMnCo)CeO₂ (Co-HEO) with the second phase of spinel is synthesized by the microwave hydrothermal method for the first time. A high efficiency of Hg⁰ removal (close to 100%) is achieved by Co-HEO catalytic oxidation at temperatures as low as 100 °C and in the atmosphere of 145 μg m^-3 Hg⁰ at a high GHSV (gas hourly space velocity) of 95,000 h^-1. According to O₂-TPD and in situ FT-IR, this extremely superior catalytic oxidation performance at low temperatures originates from the activation ability of Co-HEO to transform O₂ into superoxide and peroxide, which is promoted by point defects induced from the spinel/fluorite heterointerfaces. Meanwhile, SO₂ resistance of Co-HEO for Hg⁰ removal is also improved up to 2000 ppm due to the high-entropy-stabilized structure, construction of heterointerfaces, and synergistic effect of the multicomponents for inhibiting the oxidation of SO₂ to surface sulfate. The design strategy of the dual-phase high-entropy material launches a new route for metal oxides in the application of catalytic oxidation and SO₂ resistance.