Achieving toluene efficient mineralization over K/ɑ-MnO₂ via oxygen vacancy modulation

Oxygen vacancy plays an important role in adsorption and activation of oxygen species and therefore promotes the catalytic performance of materials in heterogeneous oxidation reactions. Here, a series of K-doped ɑ-MnO₂ materials with different K loadings were synthesized by a reproducible post processing process. Results show that the presence of K⁺ enhances the reducibility and oxygen vacancy concentration of ɑ-MnO₂ due to the break of charge balance and the formation of low valence Mn species. 4-K/MnO₂ material exhibits the highest toluene oxidation activity and satisfied long-term stability and water resistance owing to its superior reducibility and abundant surface absorbed oxygen (O_ads). In situ DRIFTS demonstrate that O_ads greatly accelerates toluene dehydrogenation rate and promotes benzoate formation, enhancing the activation and decomposition of toluene molecules. Moreover, the C[dbnd]C cleavage of benzene ring (forming maleic anhydride) is the rate-determining step of toluene oxidation, which can be easily occurred over 4-K/MnO₂.