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

Abstract

Co 3 O 4 /α-MnO 2 , Co 3 O 4 /β-MnO 2, and Co 3 O 4 /γ-MnO 2 catalysts were successfully prepared by a secondary hydrothermal method to construct interfaces between different phase MnO 2 and Co 3 O 4 , and then comparatively studied the influences of different MnO 2 -Co 3 O 4 interfaces on the properties of the obtained Co 3 O 4 /MnO 2 catalysts. Combined with the results of various characterizations, it was clear that the MnO 2 -Co 3 O 4 interface enhanced the catalytic activity of α-MnO 2 to a greater extent compared to that of β-MnO 2 -Co 3 O 4 and γ-MnO 2 . • Co 3 O 4 -MnO 2 interfaces were prepared by a secondary hydrothermal method. • The impact of MnO 2 -Co 3 O 4 interfaces mainly lay in the content of Mn 3+ . • Co 3 O 4 /α-MnO 2 exhibited high and stable activity for toluene oxidation. • Co 3 O 4 /α-MnO 2 possessed greater redox performance and maximum defect concentration. Co 3 O 4 was successfully anchored on the surfaces of different phase MnO 2 to investigate the effects of different Co 3 O 4 -MnO 2 interfaces on catalytic combustion of toluene over Co 3 O 4 /MnO 2 catalysts. The results of various characterizations illustrated that the construction of Co 3 O 4 -MnO 2 interfaces significantly increased the vacancy contents of Co 3 O 4 /MnO 2 catalysts and improved their redox properties and lattice oxygen mobility, which greatly enhanced the abilities to catalyze the oxidation of toluene. In particular, the Co 3 O 4 -MnO 2 interface showed much stronger effects on Co 3 O 4 /α-MnO 2 and Co 3 O 4 /γ-MnO 2 compared to that on β-MnO 2 , which resulted in a more significant enhancement in the catalytic activity of Co 3 O 4 /α-MnO 2 and Co 3 O 4 /γ-MnO 2 . Moreover, Co 3 O 4 /α-MnO 2 , the best catalyst, could achieve toluene conversion of 90% at 248 °C, which decreased by 22 °C in comparison with the pure α-MnO 2 . More importantly, Co 3 O 4 /α-MnO 2 could completely oxidize toluene to carbon dioxide and water at 260 °C, while α-MnO 2 could not decompose toluene thoroughly within the test temperature. The 100 h on stream test showed that the Co 3 O 4 /α-MnO 2 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 Co 3 O 4 /α-MnO 2 surface, methyl dehydrogenation and the formation of benzoate.