Enhanced photoelectrocatalytic performance of ZnO/Co3O4 nanoflowers modified TiO2 nanotube array under visible light

Abstract

The efficient degradation of organic pollutants from the water has been attracted greater public attention and remains to be the main challenge of environmental problems. In this work, ZnO/Co3O4 nanoflowers are deposited on the surface of TiO2 nanotube arrays (ZnCo-TiO2) via the one-pot hydrothermal method by adjusting the Zn/Co ratios. The images of scanning electron microscope show that the ZnCo11-TiO2 (the addition of the Zn/Co ratios is 1:1) presents nano spherical nano-flowers morphologies. In addition, the energy bandgap of ZnCo11-TiO2 is calculated to be 2.8 eV by UV–visible diffuse reflectance spectroscope, which was smaller than that of other semples. Moreover, the lowest peak intensity of photoluminescence spectroscopy for ZnCo11-TiO2 indicates that it has high electron-hole separation efficiency. From the results of UV–visible diffuse reflectance spectroscope and EIS, we can see that ZnCo11-TiO2 has a wider spectral absorption range (200–380 nm and 450–800 nm) and a smaller electron transfer impedance (137.4 Ω). The photoelectrocatalytic removal efficiencies of ZnCo11-TiO2 is 97.5% toward the removal of methylene blue (MB), which is higher than that of other semples. The excellent photoelectrocatalytic performances of ZnCo11-TiO2 are ascribed to the high visible light absorption and rapid transportation of photogenerated electrons on ZnO/Co3O4 nanoflowers. In addition, this paper tentatively stated the detailed photoelectrocatalytic mechanism of ZnCo11-TiO2 electrode for the removal of MB.