The ZnO–Au-Titanium oxide nanotubes (TiNTs) composites photocatalysts for CO2 reduction application

The presence of gold nanoparticles (Au) on the zinc oxide (Zn)-titanium oxide nanotubus (TiNTs) composites to form the Z-scheme type photocatalysts has been investigated for photocatalytic reduction of CO2 to methanol. In this study, the commercial titanium dioxide powder (P-25) was first treated under a strong basic environment and applied a hydrotherrmal method to systhsize TiNTs, and calcined to use as a support. Then, various ratios of ZnO and TiNTs from 0.1 to 0.5 were also prepared by hydrothermal method to form TiNTs-ZnO-X (TZ-X, X is equal to the ZnO/TiNTs weight ratio) composites, and 1 to 5 wt % of Au were impregnated on the TiNTs-ZnO support to form the ZnO–Au-TiNTs composite photocatalysts. The catalysts will be characterized by x-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible spectroscopy (UV–Vis) and photoluminescence spectroscopy (PL) techniques to determine the structures and morphology of the ZnO–Au-TiNTs composites. The catalytic results have revealed that the TZ-0.20–2 wt% Au catalyst has the best photocatalysis activity with a 7777.1μmole/(g-cat) (hr) CH3OH production yield. The formation of the ZnO–Au-TiNTs Z-scheme type heterostructure results in an efficient electron transfer pathway and electron-hole separation inside the composite catalyst which lead to a highly efficient CO2 reduction and excellent improvement in methanol yield.