Fabrication of rGO/α-Fe₂O₃ electrodes: characterization and use in photoelectrocatalysis

In the current study, the synthesis of hematite (α-Fe₂O₃) at different temperatures (750 and 900 °C), and reduced graphene oxide (rGO), obtained from an adaptation to the Hummers’s method, was evaluated. These materials were characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, among others. The deposition of samples on the conductive surface of tin-doped indium oxide coated glass substrate, was performed by the Layer-by-Layer technique. The films were prepared with 1- and 4-bilayers α-Fe₂O₃, using a cationic polyelectrolyte diallyldimethylammonium chloride (PDDA) or rGO. It was observed that the rGO/α-Fe₂O₃ films presented higher photocurrent and less resistivity when compared to the PDDA/α-Fe₂O₃ films. The largest photocurrent was obtained with the 4-bilayers rGO/α-Fe₂O₃ at 900 °C film, with 2.15 µA cm⁻². In addition, a kinetic study for photoelectrocatalytic decolorization of the methylene blue dye under visible light was performed. The electrode that showed the greatest photoelectroactivity was the 4-bilayers rGO/α-Fe₂O₃ at 900 °C film, resulting in k_obs = 11.90 × 10⁻³ min⁻¹ and about 78% decolorization after 120 min.