Polymorphous transformation of rod-shaped iron oxides and their catalytic properties in selective reduction of NO by NH3

摘要

Polymorphous transformation of rod-shaped gamma-Fe2O3 was applied to fabricate Fe3O4/Fe2O3 nanorods. Hydrogen reduction of gamma-Fe2O3 nanorods at 350 degrees C yielded Fe3O4 nanorods with similar size; reoxidation of the resulting Fe3O4 nanorods produced gamma-Fe2O3 at 500 degrees C and alpha-Fe2O3 nanorods at 600 degrees C. When applied to catalyze selective reduction of NO with NH3, the activity followed the order gamma-Fe2O3 > gamma-Fe2O3-500 > alpha-Fe2O3 > Fe3O4, which was well correlated with their crystalline structures. The superior performance of gamma-Fe2O3 nanorods was attributed to the simultaneous exposure of Fe3+ and O2-, which favoured the adsorption and activation of NH3 and NO molecules.