Decoding the role of oxygen defects in MnO₂-based catalysts for enhanced VOCs oxidation

Oxygen defects were essential in facilitating the catalytic oxidation process of VOCs by MnO₂. However, it remains unclear whether surface oxygen defects or bulk oxygen defects have a greater influence on the catalytic performance of MnO₂-based catalysts in VOCs oxidation. Therefore, CuO/MnO₂ with rich surface defects and CuMnO_x dominated by bulk oxygen defects were successfully prepared by a surface modification way and a hydrothermal synthesis method respectively, which was evidenced by the results of a series of characterization techniques (Raman, TEM, EPR and in situ DRIFTS, etc.) and the DFT calculation. The results of the activity evaluation showed that the effects of surface oxygen defects were decisive in improving the catalytic activity of MnO₂-based catalysts. In-situ DRIFTS patterns showed the surface oxygen defects were involved in the chemisorption and preliminary oxidation of toluene, which was the rate-determining step in the oxidative decomposition of toluene. The CuO/MnO₂ catalyst exhibited the best catalytic performance (T₅₀ = 217 °C, T₉₀ = 238 °C) compared with α-MnO₂ (T₅₀ = 253 °C, T₉₀ = 287 °C) and CuMnO_x (T₅₀ = 230 °C, T₉₀ = 259 °C). Moreover, CuO/MnO₂ illustrated excellent stability, reusability, and water resistance ability, showing great potential for industrial applications.