Fabrication of Ag nanoparticles supported on one-dimensional (1D) Mn3O4 spinel nanorods for selective oxidation of cyclohexane at room temperature

Abstract

Ag nanoparticles (with 2–5 nm size) supported on Mn₃O₄ nanorods were prepared in the presence of the cationic surfactant cetrimonium bromide using a hydrothermal method. The material was characterized in detailed by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning transmission electron microscopy-mapping, Raman spectroscopy, Fourier-transformed infrared spectroscopy and inductively coupled plasma-atomic emission spectroscopy. Electron microscopy studies revealed the formation of 1D nanorods morphology. XRD revealed the formation of Mn₃O₄ spinel phase and TEM showed that ultrasmall-sized metallic Ag-nanoparticles deposited on Mn₃O₄ spinel (nanorods). This Ag/Mn₃O₄ nanomaterial exhibited excellent catalytic activity in the cyclohexane oxidation reaction at room temperature. The impacts of various reaction parameters (e.g. time, substrate : H₂O₂ molar ratio etc.) were investigated in detail. A detailed characterization study demonstrated the correlation between the physicochemical properties of the Ag–Mn oxide nanorods and their catalytic performance. A cyclohexane conversion of 88% with 75% cyclohexanone selectivity with an overall C₆ selectivity (cyclohexanol + cyclohexanone) of 100% was accomplished at room temperature. The Ag/Mn₃O₄ catalyst hardly exhibited leaching up to eight reuses, proving its true heterogeneous nature.