Spinel (Mn, Fe)₃O₄ Nanocatalyst for the Catalytic Ozone Decomposition under Humid Conditions

The development of ozone-decomposition catalysts with high efficiency and exceptional resistance to humidity is a significant challenge, as ozone is a primary air pollutant. This study successfully synthesized a series of Mn x Fe 3– x O 4 catalysts with varying crystal structures by adjusting the Mn/Fe molar ratios through a coprecipitation method with inorganic salt precursors. Compared to crystalline Mn 3 O 4 and Fe 2 O 3, the obtained amorphous MnFe 2 O 4 (MnFe-1) nanocatalyst exhibited an optimal ozone conversion rate of 99.9% for 50 ppm O 3 with a space velocity (SV) of 600 L g –1 h –1 in dry gas and 77.4% for 50 ppm O 3 with a SV of 600 L g –1 h –1 under a relative humidity (RH) of 60%. The superior performance of the amorphous sample can be attributed not only to its smaller size and larger surface area but also to the presence of Mn 3+ as the active site, a higher number of oxygen vacancies and acid sites, and the synergistic effect between iron and manganese. This research offers a universally applicable preparation method for nanosized spinel oxides and provides an in-depth exploration of the ozone-decomposition mechanism.