Electrochemically Assisted Photocatalytic Degradation of 4-Chlorophenol by ZnFe_2O_4-Modified TiO_2 Nanotube Array Electrode under Visible Ught Irradiation

摘要

A well-aligned ZnFe_2O_4/TiO_2 composite nanotube array(ZnFe_O_4/ TlO_2-NTs) electrode with visible-light activity was successfully prepared using a two-step electrochemical process of anodization and a novel cathodic electrodeposition method followed by annealing. The ZnFe_2O_4 nanoparticles were highly dispersed inside the TiO_2-NTs but minimized at the tube entrances. The structure and optical properties of the TiO_2 nanotubes and the derived composites have been well characterized. The composites displayed a strong photo response in the visible region and low recombination rate of the electron-hole pairs. In addition, the synthesized ZnFe_2O_4/TiO_2-NTs electrode showed much higher photocurrent density in the visible region than pure TiO_2-NTs electrode. The dramatically enhanced electrochemically assisted photocatalytic activity of the composite electrode was evaluated in the decomposition of 4-chlorophenol and dichloroacetate under visible light irradiation (420 nm < λ < 600 nm). The improved photoelectrocatalytic (PEC) activity is derived from the synergetic effect between ZnFe_2O_4 and TiO_2, which promoted the migration efficiency of photogenerated carriers at the interface of the composite and enhanced the efficiency of photon harvesting in the visible region. The degradation of 4-chlorophenol was monitored by measuring Cl~- concentrations and analyzing reaction intermediates by high-performance liquid chromatography-mass spectroscopy (HPLC-MS).