Mn3O4-NiO-Ni/CNTs catalysts prepared by spontaneous redox at high temperature and their superior catalytic performance in selective oxidation of benzyl alcohol

• Mn3O4-NiO-Ni/CNTs were obtained by reduction promoted at high temperature.
• The ternary component catalyst showed superior catalytic performance.
• The existence of metallic Ni is crucial for the increase of oxidative activity.
• The structural defects of CNTs play promoting role for catalytic performance.
• CNTs exhibited much higher catalytic activity than active carbon and graphite.

Mn3O4-NiO-Ni/CNTs catalysts were synthesized via a facile spontaneous redox reaction at high temperature. The prepared catalysts were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H2-temperature programmed reduction (H2-TPR), Raman spectroscopy, nitrogen adsorption–desorption isotherm and ICP-AES. The catalytic performance was evaluated by selective oxidation of benzyl alcohol in the presence of oxygen. Comparing with monocomponent Mn or Ni species loaded on CNTs, the bicomponent Mn and Ni species loaded on CNTs showed much better catalytic performance. It was found that the part of metallic Ni, which was formed by spontaneously on CNTs at high temperature, may help to improve the catalytic oxidation because it was favorable for the adsorption and activation of molecular oxygen. Comparison of different carbon supports and the influence of defect density of CNTs on the reaction had also been discussed. The proposed route of preparing efficient multi-component catalysts via spontaneous reduction of metal oxide promoted by high temperature provided a promising choice to the synthesis and application of carbon-based catalysts.

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