Morphology-controlled synthesis of alpha-FeOOH and its derivatives

摘要

alpha-FeOOH nanocrystals were synthesized in high yield via a facile and template-free hydrothermal method at low temperature. The morphology and composition of the samples were controlled by slowly releasing the SO_4~(2-) ions from ammonium persulfate. The rod-like, bundle-like, and urchin-like alpha-FeOOH nanocrystals could be acquired respectively through a direct hydrothermal route with different quantities of SO_4~(2-) ions. The rod-like alpha-FeOOH nanocrystals obtained have a diameter of 5-25 nm and a length of 100-200 nm. When the molar ratio of iron to SO_4~(2-) was 1:1, the product was pure alpha-FeOOH phase. However, as the molar ratio was decreased from 1:1 to 1:4, pure FeSO_4OH centre dot 2H_2O phase was obtained. When the molar ratio was between 1:4 and 1:1, the prepared product was composed of two phases (alpha-FeOOH and FeSO_4OH centre dot 2H_2O). After hydrothermally aging the as-synthesized alpha-FeOOH nanorods at 180 deg C for 1 d, alpha-Fe_2O_3 nanorods were obtained. However, the edge of the alpha-Fe_2O_3 nanorods was sword-like and different from the blunt edge of alpha-FeOOH nanorods due to a recrystallization mechanism.