Visible-light-driven photocatalytic properties of ZnO/ZnFe2O4 core/shell nanocable arrays

ZnO-core/ZnFe2O4-shell nanocable arrays on the sapphire substrate were grown using a simple sacrificial ZnO-nanowire-array templating method. When comparing to pure ZnO nanowire arrays (the core only) or ZnFe2O4 nanotube arrays (the shell only), the ZnO/ZnFe2O4 nanocable arrays have demonstrated the highest photodegradation capability of rhodamine B (RhB) under visible light illumination. Although all three nanostructure arrays showed photocatalytic activities under visible light, their degradation pathway are found to be different. The least effective dye-sensitization mechanism is responsible for the RhB degradation in the presence of ZnO nanowire arrays, while the highly-reactive radicals produced by photogenerated electron-hole pairs in visible-light-excited ZnFe2O4 contributes to RhB degradation in both ZnO/ZnFe2O4 nanocable arrays and ZnFe2O4 nanotube arrays. The type II band alignment between ZnO and ZnFe2O4 leads to effective charge carrier separation in the nanocable arrays, but is absent in the case of ZnFe2O4 nanotube arrays. This explains the more efficient RhB decomposition in the presence of the ZnO-core/ZnFe2O4-shell nanocable arrays. (C) 2014 Elsevier B.V. All rights reserved.