Regulating surface properties of Co3O4@MnO2 catalysts through Co3O4-MnO2 interfacial effects for efficient toluene catalytic oxidation

Interface engineering between Co3O4 and MnO2 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 Co3+ or Co2+. Herein, Co3O4-MnO2 interface was successfully constructed on Co3O4 primarily exposed different crystal planes to design Co ions that were directly linked to MnO2 at Co3O4-MnO2 interface. Combining the results of systematic characterizations and catalytic performance evaluation, it is found that the oxidative decomposition of toluene over Co3O4@MnO2 catalysts is significantly accelerated in comparison with the pristine Co3O4, which can be attributed to the greatly increased Co3+ and adsorbed oxygen species as well as specific surface area after the successful construction of Co3O4-MnO2 heterointerface. However, Co3O4-MnO2 interface shows much greater influence on Co3O4@MnO2-100 where Co ions mainly exist in the form of Co2+ than that on Co3O4@MnO2-110 dominated by Co3+. Furthermore, catalytic performance evaluation results illustrate that the T90 of Co3O4@MnO2-110 has only decreased by 11 °C compared to Co3O4-110, while the T90 of Co3O4@MnO2-100 is 50 °C lower than that of Co3O4-100. Therefore, based on the above results it speculates that the strong interaction between MnO2 and Co3O4 at Co3O4-MnO2 hetero-interface may originate more from the synergistic effect between MnO2 species and Co2+ ions. In addition, the in-situ DRIFTS demonstrate that the oxidation of toluene over Co3O4@MnO2 catalysts follows the path of toluene → benzaldehyde → benzoate → maleic anhydride → water and carbon dioxide.