Template-Free Hydrothermal Synthesis of Hollow α-FeOOH Urchin-Like Spheres and Their Conversion to α-Fe2O3 Under Low-Temperature Thermal Treatment in Air

Hollow alpha-FeOOH urchin-like spheres were synthesized by a simple hydrothermal method at 160 A degrees C for 12 h and their thermal conversion to hollow alpha-Fe2O3 urchin-like spheres was performed at 300 A degrees C for 2 h in air. The results from X-ray diffraction and electron microscopy analyses reveal that hollow alpha-FeOOH urchin-like spheres were completely transformed to hollow alpha-Fe2O3 urchin-like spheres without a significant morphological change. Also, the effect of hydrothermal treatment temperature (170-200 A degrees C for 12 h) on the phase structure and morphology of the final product was investigated. Pure alpha-FeOOH, the mixture of alpha-FeOOH and alpha-Fe2O3, and pure alpha-Fe2O3 with different morphologies were obtained at < 180, 180-190 and 200 A degrees C, respectively. The obtained materials can be used in the photodegradation of organic pollutants under visible light irradiation.