Preparation of graphene/TiO2 nanotube array photoelectrodes and their photocatalytic activity for the degradation of alachlor

Abstract

Graphene/TiO₂ nanotube array (GR/TNA) photoelectrodes were fabricated by combining in situ anodization and an electro-deposition process. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectra (DRS), photopotential measurement, electrochemical impedance spectroscopy (EIS) and zeta-potential measurement were employed to characterize the as-prepared samples. The photocatalytic properties of the GR/TNA photoelectrodes were investigated using the degradation of alachlor as a model reaction. The introduction of GR had no obvious effect on the original crystallization of the TNAs, whereas the photoelectric property was significantly improved. The GR/TNA photoelectrodes exhibited higher photocatalytic activity for alachlor degradation than the bare TNA photoelectrodes. The degradation efficiency of alachlor by the GR/TNA photoelectrodes gradually decreased with the increase of initial alachlor concentration, initial pH and distance from illuminant. Some interfering anions (e.g. NO₃⁻ and SO₄²⁻) could improve the photocatalysis efficiency, whereas Cl⁻ exhibited a slight inhibition effect on the alachlor degradation. Additionally, GR/TNA photoelectrodes possessed superb stability for maintaining a high alachlor degradation efficiency at more than 99.5% after 15 times of successive use with 60 min irradiation for each cycle.