Regulating surface properties of Co 3 O 4 @MnO 2 catalysts through Co 3 O 4-MnO 2 interfacial effects for efficient toluene catalytic oxidation

Interface engineering between Co 3 O 4 and MnO 2 shows distinct advantages in regulating the surface properties of catalysts. However, there is still doubt about whether the interfacial effects originate from the interaction between heterogeneous metals and Co 3+ or Co 2+ . Herein, Co 3 O 4 -MnO 2 interface was successfully constructed on Co 3 O 4 primarily exposed different crystal planes to design Co ions that were directly linked to MnO 2 at Co 3 O 4 - MnO 2 interface. Combining the results of systematic characterizations and catalytic performance evaluation, it is found that the oxidative decomposition of toluene over Co 3 O 4 @MnO 2 catalysts is significantly accelerated in comparison with the pristine Co 3 O 4 , which can be attributed to the greatly increased Co 3+ and adsorbed oxygen species as well as specific surface area after the successful construction of Co 3 O 4 -MnO 2 heterointerface. However, Co 3 O 4 -MnO 2 interface shows much greater influence on Co 3 O 4 @MnO 2 -100 where Co ions mainly exist in the form of Co 2+ than that on Co 3 O 4 @MnO 2 -110 dominated by Co 3+ . Furthermore, catalytic performance evaluation results illustrate that the T 90 of Co 3 O 4 @MnO 2 -110 has only decreased by 11 degrees C compared to Co 3 O 4 -110, while the T 90 of Co 3 O 4 @MnO 2 -100 is 50 degrees C lower than that of Co 3 O 4 -100. Therefore, based on the above results it speculates that the strong interaction between MnO 2 and Co 3 O 4 at Co 3 O 4 -MnO 2 hetero -interface may originate more from the synergistic effect between MnO 2 species and Co 2+ ions. In addition, the in -situ DRIFTS demonstrate that the oxidation of toluene over Co 3 O 4 @MnO 2 catalysts follows the path of toluene -> benzaldehyde -> benzoate -> maleic anhydride -> water and carbon dioxide.