Hematite homogeneous core/shell hierarchical spheres: Surfactant-free solvothermal preparation and their improved catalytic property of selective oxidation

Solvothermal synthesis is an efficient synthetic method for preparing nano and micromaterials. Preparation of hematite through alcoholysis of ferric ion under solvothermal condition has been carried out at low concentrations. In this paper, Fe2O3 homogeneous core/shell hierarchical nanostructures were synthesized via solvothermal treatment of FeCl3·6H2O and ethanol. The achievements of such structures can be attributed to two important factors: high temperature and high concentration. Besides, the crystal water and reaction time were also important factors to the synthesis of hematite. The prepared samples were characterized using X-ray powder diffraction, Raman spectra, scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer, transmission electron microscopy and Brunauer–Emmett–Teller surface area and pore size distribution. X-ray photoelectron spectroscopy showed a satellite peak at 719.8 eV, which is the characteristic peak of Fe(III). The formation mechanism of the spheres and the effects of the reactant concentrations and reaction temperatures have been discussed. Moreover, the enhanced catalytic activity of the spheres has also been investigated through oxidation of benzyl alcohol to benzaldehyde with high conversion (42%) and selectivity (95%). - Graphical abstract: Fe2O3 homogeneous core/shell hierarchical microspheres were synthesized by solvothermal method. Owing to the special structure, the synthesized Fe2O3 microspheres exhibit a superior catalytic activity in benzyl oxidation. Highlights: ► Hierarchical Fe2O3 core/shell microspheres were synthesized. ► Microspheres were assembled by β-FeOOH. ► The sample exhibits a superior catalytic activity and selectivity. ► The high activity and selectivity are due to the hierarchical core/shell structure.