Nanodispersed Mn₃O₄/γ-Al₂O₃ for NO₂ Elimination at Room Temperature

Adsorption is an efficient method for atmospheric NO x abatement under ambient conditions; however, traditional adsorbents suffer from limited adsorption capacity and byproduct formation. Developing a low-cost material with high capacity for atmospheric NO 2 elimination remains a challenge. Here, we synthesized a nanodispersed Mn 3 O 4 /γ-Al 2 O 3 (Mn/Al) material that exhibits excellent ability to remove NO 2 . The 10 wt % Mn/Al sample showed the highest removal capacity, with 247.6 mg NO 2 /g Mn/Al, which is superior to that of activated carbon (42.6 mg NO 2 /g). There were no byproducts produced when Mn/Al was tested with ppb-level NO 2 . The NO 2 abatement mechanism with Mn/Al is different from physisorption or chemisorption. NO 2 removal is mainly a catalytic process in air, during which surface hydroxyls and lattice oxygen are involved in the oxidation of NO 2 to nitrate. In contrast, a chemical reaction between Mn 3+ and NO 2 is dominant in N 2, where Mn 3+ is converted into Mn 4+ and NO 2 is reduced to nitrite. Washing with deionized water is an effective and convenient method for the regeneration of saturated Mn/Al, and an 86% adsorption capacity was recovered after one washing. The results suggest that this low-cost Mn/Al material with easy preparation and regeneration is a promising candidate material for atmospheric NO 2 elimination.