The electrical conductivity and photocatalytic activity of ultrafine iron hydroxide/oxide systems

Abstract

The ultrafine iron hydroxide/oxide systems are fabricated by a hydro- thermal approach, using iron nitrate and citric acid as precursors. The phase composition, crystal and magnetic microstructures, morph- ology, conductivity, and optical properties are characterized by X-ray diffraction, scanning electron microscope, impedance spectroscopy, M € ossbauer spectroscopy, and UV-VIS spectroscopy. The mechanisms of phase transformation of amorphous ultrafine c-FeOOH ! nano- composite c-Fe 2 O 3 /a-Fe 2 O 3 in the temperature interval 150 – 350 j are established. The photocatalytic activity of samples was estimated by the degradation of methylene blue and formaldehyde under UV or visible light in an aqueous solution. The results indicate that the photocatalytic degradation activities of amorphous c-FeOOH and nanocomposite c-Fe 2 O 3 /a-Fe 2 O 3 are higher than that of phase pure c-Fe 2 O 3 . The photocatalytic property of samples is related to their conductivity and band gap. This implies that a synergistic effect exists between the conductivity and the photocatalytic activity in the ultrafine iron hydroxide/oxide systems. In addition, it can be attrib- uted to the active heterogeneous Fenton process for c -FeOOH and the microstructure of c-Fe 2 O 3 /a-Fe 2 O 3 , which is probably caused by a successful combination of electronic structures of the phases of mag- netite and hematite.