Revealing oxygen transfer between Mn3O4 and CuMn2O4 and its effect on enhanced catalytic oxidization of VOCs

Hybrid catalysts are widely utilized in various environmental catalysis, such as catalytic oxidization and reduction. However, most works usually treat a hybrid catalyst as a whole, and seldom report explores interface behavior of active species between components in the hybrid. In this work, we investigated mechanism for enhanced catalytic oxidization of toluene by a mixture of Mn3O4 and CuMn2O4. The mixture removed 99% of toluene at 240 °C, far bigger than CuMn2O4 (53%) and Mn3O4 (23%). In brief, Mn3O4 had plenty of bulk lattice oxygens, which were inactive for toluene catalytic oxidization. After forming an interface between Mn3O4 and CuMn2O4, oxygen vacancy formed on the interface during the catalysis, and transferred the bulk lattice oxygen to the interface, forming active lattice oxygen. Therefore, the number of active sites was increased, resulting in an enhanced catalytic performance. This conclusion was verified in other hybrids, including Mn3O4/CuFeOx, Mn3O4/CuCeOx, and Mn3O4/CuCoOx. The main result of this work helps to understand the catalytic mechanism of volatile organic compounds by hybrid oxides. These results are also in favor of designing and optimizing catalysts.