Capability of novel ZnFe2O4 nanotube arrays for visible-light induced degradation of 4-chlorophenol

Highly ordered ZnFe2O4 nanotube arrays were successfully prepared by anodic aluminum oxide templates from sol–gel solution. The results from environmental scanning electron microscopy and X-ray photoemission spectroscopy indicated that the as-prepared samples were vertically aligned spinel ZnFe2O4 nanotube arrays, and the nanotubes were uniform along the axial direction with an average diameter of approximately 200 nm. The absorption edge of ZnFe2O4 nanotube arrays shifted to a higher energy in the UV–Vis absorption spectrum compared with that of ZnFe2O4 nanoparticles film. The synthesized ZnFe2O4 nanotube arrays exhibited excellent photocatalytic capability for degradation of 4-chlorophenol under visible-light irradiation. The main intermediate degradation species of 4-chlorophenol identified by liquid chromatography-mass technique were benzoquinone, hydroquinone, hydroxybenzoquinone and 2-peroxy-o-dihydroxybenzene. The degradation pathways of 4-chlorophenol under visible-light irradiation was derived and discussed by interpreting the observations of the intermediate species in the photocatalytic reactions.