Green rusts-derived iron oxide nanostructures catalyze NO reduction by CO

Abstract

Green rusts with brucite-like layers of hydroxide intercalated with anions constitute a family of diverse precursors for the synthesis of iron oxides via dehydration, but precise structural control of the resulting oxides with respect to the size and shape at the nanometer level remains challenging due to the easy oxidation of the ferrous species. Herein, we report a new synthetic strategy for the facile preparation of fibrous-like green rusts by using appropriate balancing anions (CO32− and SO42−) in ethylene glycol to regulate the morphology. Depending on the type of the intercalating anion, the green rusts were converted into hematite with fibrous- or plate-like shapes upon thermal activation. When evaluated in the reaction of NO reduction by CO, these iron oxides showed a prominent shape-dependent catalytic behavior. The fibrous-like Fe2O3 was much more catalytically active and structurally robust than the plate-like analogue. Combined spectroscopic and microscopic characterizations on the nanostructured iron oxides revealed that the superior performance of the fibrous-like Fe2O3 stemmed from a facile Fe2O3/Fe3O4 redox cycle and a higher density of active sites for NO activation.