Enhanced catalytic performance for toluene purification over Co3O4/MnO2 catalyst through the construction of different Co3O4-MnO2 interface

Co3O4 was successfully anchored on the surfaces of different phase MnO2 to investigate the effects of different Co3O4-MnO2 interfaces on catalytic combustion of toluene over Co3O4/MnO2 catalysts. The results of various characterizations illustrated that the construction of Co3O4-MnO2 interfaces significantly increased the vacancy contents of Co3O4/MnO2 catalysts and improved their redox properties and lattice oxygen mobility, which greatly enhanced the abilities to catalyze the oxidation of toluene. In particular, the Co3O4-MnO2 interface showed much stronger effects on Co3O4/alpha-MnO2 and Co3O4/gamma-MnO2 compared to that on beta-MnO2, which resulted in a more significant enhancement in the catalytic activity of Co3O4/alpha-MnO2 and Co3O4/gamma-MnO2. Moreover, Co3O4/alpha-MnO2, the best catalyst, could achieve toluene conversion of 90% at 248 degrees C, which decreased by 22 degrees C in comparison with the pure alpha-MnO2. More importantly, Co3O4/alpha-MnO2 could completely oxidize toluene to carbon dioxide and water at 260 degrees C, while alpha-MnO2 could not decompose toluene thoroughly within the test temperature. The 100 h on stream test showed that the Co3O4/alpha-MnO2 had excellent stability and was a catalyst with great potential in practical applications. In addition, the in-situ DRIFTS results also showed that the presence of abundant oxygen vacancies contributes to the adsorption of toluene on the Co3O4/alpha-MnO2 surface, methyl dehydrogenation and the formation of benzoate.