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• 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]

A series of Ce-M(Cu, Co and Fe) catalysts were synthesized via sol–gel methods. In situ DRIFTS was introduced to explored the process of toluene degradation, confirming oxygen vacancies played an important role. [Display omitted] • Ce-Cu sample exhibited best catalytic activity and stability for toluene oxidation. • Superb activity was attributed to high Ce3+/ Ce4+ and high O ads /O latt. • The oxygen vacancies were modulated by different metal doping. • Benzoic acid was key intermediates in toluene catalysis by in situ DRIFT analysis. A series of CeO 2 samples modified with various metals M (M = Cu, Co and Fe) were synthesized via a simple sol–gel approach. The experimental results showed that there were significant differences in the catalytic activities between different metal-doped Ce-based catalysts. The Ce-Cu sample possessed excellent catalytic activity at low temperatures, and 90 % conversion of toluene was at 255 ℃, which was due to the presence of ample oxygen vacancies (O v). Three degradation pathways for toluene oxidation were inferred based on the in situ DRIFTS. The Ce-Cu catalysts possessed abundant O v , which improved the conversion between O ads → O latt and the breakage of aromatic rings, thus reducing the production of intermediates. The Ce-Co and Ce-Fe catalysts owned few amounts of O v species, leading to an extensive amount of by-products. Furthermore, the loss of active sites inhibited the reaction rate, causing the inferior catalytic performance of the Ce-Co and Ce-Fe samples. [ABSTRACT FROM AUTHOR]