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

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.