Infrared spectra of CO adsorbed on prismatic faces of α-Fe2O3
Crystallites of α-Fe2O3 prepared by thermal decomposition of α-FeO(OH) have regular needle-like shape with statistically predominant prismatic faces (as shown by HRTEM and SAED patterns). The i.r. spectrum of CO adsorbed at 77 K on these microcrystals is characterized by a single peak at 2165.5 cm–1 which is assigned to the stretching mode of CO σ-bonded on Fe3+ ions, with negligible contribution of metal–C back-donation. The frequency of the band shifts with the coverage: this is due to the building up of lateral interactions (dynamic and static) between the oscillators adsorbed on the prismatic faces.