A facile two-step fabrication of titanium dioxide coated copper oxide nanowires with enhanced photocatalytic performance

Abstract

Copper oxide (CuxO) nanostructures coated with the titanium dioxide (TiO2) are expected to improve the charge separation efficiency and photoactivity in the photosynthesis and pollutant treatment. In this study, as an alternative fabrication method, CuxO nanowires coated with TiO2 have been produced by thermal oxidation of the copper foil at different temperatures (400-600 degrees C) and times (2 and 4 h) in ambient conditions and subsequently, hydrolyzed in different molar concentrations (20, 40 and 80 mM) on CuO nanowires by immersing and then heat treating the mixture of titanium (IV) isopropoxide and isopropyl alcohol. The characteristics of the CuxO/TiO2 nanostructures were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM). The results showed that the CuO layer was peeled off from the copper foil in the thermal oxidation process which was carried out at a temperature higher than 500 degrees C and for > 2 h. The ideal temperature/time for high nanowire density and aspect ratio of CuO nanowire growth is 450 degrees C for 2 h. TEM-SAED diffraction pattern of TiO2 coating surface belongs to anatase crystal phase for all prepared samples. Thickness of TiO2 coating increased with increasing concentration but in the highest concentration (80 mM), Ti was not coated on the CuO nanowire and diffuses into the interior. For 20 mM and 40 mM concentration prepared CuxO/TiO2 nanostructures, measured coating thickness was about to 2 nm and 10 nm, respectively. Photocatalytic activity of CuxO/TiO2 catalysts was evaluated by measuring the rate of photodegradation reaction of Reactive Red (RR180) azo dyes under UVA-light. As a result, the CuxO/TiO2 catalyst which was subjected to thermal oxidation at 450 degrees C for 2 h and hydrolyzed in 40 mM solution shows the highest degradation rate of 35%. It is clearly stated that the degradation rate is highly dependent on nanowire density, nanowire aspect ratio and coated layer thickness.