Enhanced catalytic oxidation of toluene over amorphous cubic structured manganese oxide-based catalysts promoted by functionally designed Co–Fe nanowires†

Abstract

Manganese oxide with a special cubic structure grown on Co–Fe nanowire (NW)-coated nickel foam (Mn/Co–Fe/NF) was successfully fabricated by a facile hydrothermal method and applied as an efficient catalyst for the oxidation of toluene. The obtained catalysts were systematically analyzed by XRD, SEM, TEM, H₂-TPR, O₂-TPD, XPS and Raman characterization. It was found that the uniform Co–Fe nanowires (NWs) formed on the NF not only promoted the distribution of the supported manganese oxide cubes but also played an important role in the tuning of the manganese valences and oxygen species in the catalyst. The strong interaction between the Co–Fe NWs and the Mn species with the MnCO₃ cubic structure was proven to enhance the reducibility, the generation of both active surface oxygen and lattice oxygen species and the defective structure of the catalysts. Among all the prepared catalysts, the 5Mn/Co–Fe/NF catalyst with an appropriate loading amount of Mn species exhibited a complete toluene conversion temperature of 256 °C following the MVK mechanism. It is considered that this high catalytic performance should be contributed by its enhanced low-temperature reducibility, increased surface and lattice oxygen species, and the enriched active species of Mn⁴⁺/Mn³⁺ and Co³⁺/Co²⁺ on the catalyst surface. In addition, the 5Mn/Co–Fe/NF catalyst exhibited excellent stability as well as water resistance. This work provides new insight into the promising application of such a catalyst for the effective catalytic oxidation of VOCs.