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The CeMo catalysts were prepared via different method and employed for the catalytic combustion of toluene. The influence of different preparation methods on CeMo samples for toluene oxidation was revealed. The toluene catalytic oxidation efficiency followed an order of CeMo-HT > CeMo-CP > CeMo-Sg. The long-term test indicated that the CeMo-HT possessed outstanding thermal stability. The excellent catalytic activity of CeMo-HT could be reasonably attributed to the smallest grain size, the highest number of low valence Ce3+ ions and O sur species. CeMo-HT catalyst prepared by the hydrothermal method possessed the richer oxygen vacancies, which promoted the deep oxidation of toluene, and effectively reduced the production of intermediates. However, CeMo-HT (aged) possessed poorer oxygen vacancies, and generated more by-products. Additionally, the two reaction pathways of the toluene were inferred. In pathway I for CeMo-HT (aged): toluene → benzyl alcohol → benzaldehyde → benzoic acid →carbonate → CO 2 and H 2 O. In pathway II for CeMo-HT: toluene → phenol → benzoquinone → maleic anhydride → CO 2 and H 2 O. [Display omitted] • CeMo-HT sample exhibited best catalytic activity and stability for toluene oxidation. • Superb activity was attributed to high Ce3+/ Ce4+ and high O Sur /O total. • The oxygen vacancies were simply modulated by the preparation method. • Benzoic acid and phenol were key intermediates in toluene catalysis by in situ infrared analysis. [ABSTRACT FROM AUTHOR]

• K-doped MnO 2 was synthesized by different strategies. • K+ has structural promoting and electronic regulating effects in metal oxides. • Oxygen vacancies could be tuned by changing the preparation method and potassium source. • The MVK mechanism and the in situ DRIFT was used to study the reaction pathway. Alkali metal potassium was beneficial to the electronic regulation and structural stability of transition metal oxides. Herein, K ions were introduced into manganese oxides by different methods to improve the degradation efficiency of toluene. The results of activity experiments indicated that KMnO 4 -HT (HT: Hydrothermal method) exhibited outstanding low-temperature catalytic activity, and 90% conversion of toluene can be achieved at 243°C, which was 41°C and 43°C lower than that of KNO 3 -HT and Mn-HT, respectively. The largest specific surface area was observed on KMnO 4 -HT, facilitating the adsorption of toluene. The formation of cryptomelane structure over KMnO 4 -HT could contribute to higher content of Mn3+ and lattice oxygen (O latt), excellent low-temperature reducibility, and high oxygen mobility, which could increase the catalytic performance. Furthermore, two distinct degradation pathways were inferred. Pathway Ⅰ (KMnO 4 -HT): toluene → benzyl → benzoic acid → carbonate → CO 2 and H 2 O; Pathway ⅠⅠ (Mn-HT): toluene → benzyl alcohol → benzoic acid → phenol → maleic anhydride → CO 2 and H 2 O. Fewer intermediates were detected on KMnO 4 -HT, indicating its stronger oxidation capacity of toluene, which was originated from the doping of K+ and the interaction between K O Mn. More intermediates were observed on Mn-HT, which can be attributed to the weaker oxidation ability of pure Mn. The results indicated that the doping of K+ can improve the catalytic oxidation capacity of toluene, resulting in promoted degradation of intermediates during the oxidation of toluene. The doping of K+ had a certain influence on the morphology of MnO 2 , and the activity was significantly improved. In addition, KMnO 4 -HT possessed higher Mn3+ and O latt content, which accelerates the breaking speed of C C bonds and promotes the deep oxidation of toluene. [Display omitted] [ABSTRACT FROM AUTHOR]