Fr Francium

α- and γ-Fe₂O₃ nanorods have been prepared from a β-FeOOH precursor that was obtained by aqueous-phase precipitation of ferric chloride. The oxyhydroxide precursor had a rodlike shape with a diameter of 30–40 nm and a length of 400–500 nm. Calcination at 500 °C of the rod-shaped oxyhydroxide in air yielded α-Fe₂O₃ nanorods, whereas heating to reflux in polyethylene glycol (PEG) at 200 °C resulted in the formation of γ-Fe₂O₃ nanorods. Both oxides inherited the rodlike morphology of the precursor but exposed different crystalline facets. When being used to catalyze NO reduction by CO, an environmentally important reaction in NO abatement, the γ-Fe₂O₃ nanorods were much more active than the α-Fe₂O₃ nanorods and showed an apparent crystal-phase effect. This was because the γ-Fe₂O₃ nanorods simultaneously exposed iron and oxygen ions on their surfaces, which facilitated the adsorption and activation of NO and CO molecules.

α- and γ-Fe₂O₃ nanorods were obtained by proper dehydration of a rod-shaped β-FeOOH precursor. The Fe₂O₃ nanorods showed a distinct crystal-phase effect in the reduction of NO by CO on the basis of their exposed surface facets.