Abstract
In this work, we report on the enhanced photocatalytic activity of ZnO nanowires (NWs) modified with cuprous oxide and silver nanoparticles (NPs). ZnO NWs were first grown on fluorine-doped tin oxide substrates by thermal evaporation without catalysts. They were then modified with cuprous oxide or silver NPs, or both, by photoreduction. The NP modified NWs show better photocatalytic performance than as-grown NWs. Furthermore, ZnO NWs co-modified with cuprous oxide and silver NPs have the best photocatalytic efficiency. From the scanning electron microscopy and transmission electron microscopy images, the morphologies and the structures of the NPs are confirmed. The ultraviolet emissions of modified ZnO NWs decrease in the photoluminescence spectra, revealing that the recombination of electron-hole pairs is reduced. The absorption spectra show that modified ZnO NWs have higher absorption in both visible and ultraviolet regions, which is due to the narrow band gap of cuprous oxide NPs and the plasmonic effect of silver NPs. The photocatalytic activities of the NWs were evaluated by degrading a 50 µM rhodamine B solution under the illumination of a 100 W halogen lamp. The zeroth-order kinetic constant of the co-modified ZnO NWs is 0.32 µM/min, which is 3.2 times as high as that of as-grown ZnO NWs. The co-modified NW sample has also been tested under direct sunlight illumination. A kinetic constant of 0.73 µM/min and a degradation efficiency of 95% in 80 min have been obtained.