The Effects of Mn²⁺ Precursors on the Structure and Ozone Decomposition Activity of Cryptomelane-Type Manganese Oxide (OMS-2) Catalysts

The effects of Mn²⁺ precursors on the structure and ozone decomposition activity of cryptomelane-type manganese oxide (OMS-2) catalysts were investigated under high-humidity conditions. The OMS-2 catalysts were synthesized using a hydrothermal approach. Characterization of OMS-2 was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), N₂ physical adsorption, Raman spectroscopy, X-ray absorption fine structure (XAFS), H₂ temperature-programmed reduction (H₂-TPR), and inductively coupled plasma (ICP) spectroscopy. The OMS-2-Ac synthesized using MnAc₂ as a Mn²⁺ precursor showed the best catalytic activity for ozone decomposition (∼80%) under RH = 90% and space velocity of 600000 h^–1 and is a promising catalyst for purifying waste gases containing ozone under high-humidity conditions. Acetate groups could prevent the aggregation of manganese oxide particles, which may introduce more crystalline defects. On the basis of the characterization results, it is supposed that the greater surface area and higher amount of Mn³⁺ are the main factors that contribute to the excellent performance of OMS-2-Ac. This study can improve our understanding of ozone decomposition on OMS-2 catalysts and serve as a guide in using OMS-2 for ozone removal.