Enhancing photocatalytic activity of ZnO nanowires by embedding ITO layer as a photogenerated electron collecting layer

The photocatalytic performance of a semiconductor is strongly limited by the inefficient separation of photogenerated carries. In this work, an indium tin oxide (ITO) layer was introduced before the conventional growth of vertically aligned ZnO nanowires by chemical vapor deposition using Al-doped ZnO (AZO) as a seed layer on glass substrates. The ITO layer behaving as an efficient collecting layer of photogenerated electrons strongly suppressed the recombination of photogenerated electrons and holes, which was confirmed by the photoluminescence spectra. The UV-induced photocatalytic activities in aqueous solution were evaluated by selecting rhodamine B as the model contaminant. The ZnO nanowires with ITO layer exhibited notably enhanced photocatalytic activity, which was 9.65 times faster than that of ZnO nanowires alone. It has been proposed that the organic molecules were mainly oxidized by holes concentrated in the valence band of ZnO due to the efficient collection of electrons by ITO layer. Our work highlights that addition of electron collecting layer provides an efficient method to enhance the activity of semiconductor photocatalysts.