Influence of Mn valence state and characteristic of TiO2 on the performance of Mn–Ti catalysts in ozone decomposition

The effects of physicochemical properties of Mn–Ti catalysts on O3 conversion were examined. The catalysts were prepared by a wet impregnation method that gave manganese supported on various commercial sources of TiO2. The properties of the catalysts were studied using physicochemical techniques, including Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA). The O3 decomposition tests of Mn–Ti catalysts with various manganese loadings revealed that the 10 wt% manganese catalyst exhibited optimal, excellent activity. The O3 conversion and Mn valence state of the Mn–Ti catalysts were different, depending on the structure of the TiO2 source. Increasing the O/Ti surface atomic ratio in TiO2 increased the Mn3+ ratio. The Mn3+ ratio directly affected the O3 decomposition activity of the Mn–Ti catalyst. When the Mn3+ ratio was the largest, the catalyst showed the highest activity in O3 decomposition. The valence state of Mn exposed to the surface was a critical factor in O3 decomposition by Mn–Ti catalysts.