Electrochemical method for synthesis of a ZnFe₂O₄/TiO₂composite nanotube array modified electrode with enhanced photoelectrochemical activity

An electrode with intimate and well-aligned ZnFe2O4/TiO2composite nanotube arrays is prepared via electrochemical anodization of pure titanium foil in fluorine-containing ethylene glycol, followed by a novel cathodic electrodeposition method. The deposition of ZnFe2O4is promoted in the selfaligned, vertically oriented TiO2nanotube arrays but minimized at the tube entrances. Thus, pore clogging is prevented. Environmental scanning electron microscopy, energy-dispersive X-ray spectra, high-resolution transmission electron microscopy, X-ray diffraction patterns, and X-ray photoelectron spectroscopy indicate that the as-prepared samples are highly ordered and vertically aligned TiO2nanotube arrays with ZnFe2O4nanoparticles loading. The TiO2nanotubes are anatase with the preferential orientation of <101> plane. Enhanced absorption in both UVand visible light regions is observed for the composite nanotube arrays. The current-voltage curve of ZnFe2O4-loaded TiO2nanotube arrays reveals a rectifying behavior. The enhanced separation of photoinduced electrons and holes is demonstrated by surface photovoltage and photocurrent measurements. Meanwhile, the photoelectrochemical investigations verify that the ZnFe2O4/TiO2composite nanotube array modified electrode has a more effective photoconversion capability than the aligned TiO2nanotube arrays alone. In addition, the photoelectrocatalytic ability of the novel electrode is found enhanced in the degradation of 4-chlorophenol. KGaA, Weinheim.