Enhancing catalytic toluene oxidation over MnO2@Co3O4 by constructing a coupled interface

Abstract

Herein, a bottom-down design is presented to successfully fabricate ZIF-derived Co3O4, grown in situ on a one-dimensional (1D) α-MnO2 material, denoted as α-MnO2@Co3O4. The synergistic effect derived from the coupled interface constructed between α-MnO2 and Co3O4 is responsible for the enhanced catalytic activity. The resultant α-MnO2@Co3O4 catalyst exhibits excellent catalytic activity at a T90% (temperature required to achieve a toluene conversion of 90%) of approximately 229 oC, which is 47 and 28 °C lower than those of the pure α-MnO2 nanowire and Co3O4-b obtained via pyrolysis of ZIF-67, respectively. This activity is attributed to the increase in the number of surface-adsorbed oxygen species, which accelerate the oxygen mobility and enhance the redox pairs of Mn4+/Mn3+ and Co2+/Co3+. Moreover, the result of in situ diffuse reflectance infrared Fourier transform spectroscopy suggests that the gaseous oxygen could be more easily activated to adsorbed oxygen species on the surface of α-MnO2@Co3O4 than on that of α-MnO2. The catalytic reaction route of toluene oxidation over the α-MnO2@Co3O4 catalyst is as follows: toluene → benzoate species → alkanes containing oxygen functional group → CO2 and H2O. In addition, the α-MnO2@Co3O4 catalyst shows excellent stability and good water resistance for toluene oxidation. Furthermore, the preparation method can be extended to other 1D MnO2 materials. A new strategy for the development of high-performance catalysts of practical significance is provided.