Characterization of the thermal decomposition products of δ-FeOOH by Fourier-transform infrared spectroscopy and N2adsorption

The surface and pore structures of the materials resulting on outgassing the colloidal δ-FeOOH particles at different temperatures in the range 50–300 °C have been investigated by a variety of techniques. The FTIR spectrum of the particles outgassed at 100 °C has a weak broad band at 3650 cm–1 and a strong band at 3150 cm–1 which are assigned to the surface and bulk OH groups of δ-FeOOH, respectively. When outgassed above 150 °C three bands appear at 3665, 3635 and 3400 cm–1. The former two bands and the latter one can be assigned to the surface OH groups and the H2O molecules adsorbed in the micropores, respectively. Increasing the outgassing temperature develops the microporosity of the products. The t-plots of the samples treated above 150 °C indicate the formation of micropores with a 0.8 nm width as confirmed by transmission electron microscopy (TEM).