A Novel Hydrothermal Approach for the Synthesis of Flower-Like Fe 2 O 3 /fe Foam Nanocrystals and Their Superior Performance in Fisher–Tropsch Synthesis

A novel and facile hydrothermal approach was developed for the synthesis of three-dimensional flower-like α-Fe2O3 nanocrystals grown directly on Fe substrate using Fe(NO3)3 and hexamethylenetetramine as precursors in aqueous medium. A reaction mechanism for the synthesis and growth of the flower-like α-Fe2O3 nanocrystals was proposed to explain the effects of reaction time and temperature on the morphology and structure of the as-synthesized nanocrystals. Moreover, cube-like shapes of Fe2O3 nanocrystals were produced when urea used as hydrolysis reagent during the synthesis process. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction were employed to confirm the unique morphology, high crystallinity and pure phase structure. The as-synthesized flower-like α-Fe2O3 nanocrystals displayed a higher activity and C2–4 olefin/paraffin ratio in Fisher–Tropsch synthesis than the cube-like shape of α-Fe2O3 nanocrystals, possibly due to their high specific surface area as well as diversity of catalytic active sites.