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 o C, 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 Mn 4+ /Mn 3+ and Co 2+ /Co 3+ . 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.

Recent progresses in the synthesis of MnO2 nanowire and its application in environmental catalysis

“… 115–119 For example, as regards the α-MnO 2 @Co 3 O 4 catalyst, the heterogeneous interface constructed by MnO 2 nanowires and Co 3 O 4 nanoparticles could not only enhance the redox pair of Mn 4+ /Mn 3+ and Co 2+ /Co 3+ but also strengthen the adsorption of oxygen on the surface and accelerate the fluidity of oxygen. As a result, the catalytic activities of α-MnO 2 @Co 3 O 4 toward the oxidation of benzene 31 and toluene 120 were much better than that of pristine MnO 2 nanowires. The α-MnO 2 nanowire@Co 3 O 4 could reduce the T 90 of benzene oxidation to 247 °C (see Fig.…”

“…The catalytic performance of the toluene oxidation was also influenced by the interface between different metal oxides. Ren et al 120 fabricated ZIF-derived Co 3 O 4 grown in situ on 1D α-MnO 2 materials (as displayed in Fig. 15 ) and used it as the catalyst for toluene oxidation.…”

“…In addition, the α-MnO 2 @Co 3 O 4 catalyst also exhibited excellent stability and water resistance during the toluene oxidation. 120 Zhang et al 155 found that the fluorine (F)-doped titanium dioxide (TiO 2 ) coupled with a small number of α-MnO 2 nanowires could effectively improve the photocatalytic degradation effect of toluene. Specifically, the toluene degradation efficiency before coupling was about 90%, and the toluene degradation efficiency after coupling was increased to 96%.…”

MnO2‐Based Materials for Environmental Applications

“…Ye et al. [ 212 ] constructed MnO 2 /Co 3 O 4 binary heterojunctions with coupling interfaces by making Co 3 O 4 derived from zeolitic imidazolate framework (ZIF) in situ growing on 1D α‐MnO 2 ( Figure a). This catalyst showed excellent catalytic performance for toluene oxidation, which can be ascribed to the increased number of oxygen species adsorbed on the surface, the acceleration of oxygen migration speed, and the improvement of the redox pairs of Mn 4+ /Mn 3+ and Co 2+ /Co 3+ .…”

“…a) Reproduced with permission. [ 212 ] Copyright 2020, Elsevier. b) Fabrication schematic illustration of 3D Co 3 O 4 @MnO 2 binary semiconductor heterostructure grown on Ni foam.…”