Preparation and Photocatalytic of Nanoneedle Bi/ZnWO₄ by Two-Step Hydrothermal Method

Nanoneedle Bi/ZnWO₄ photocatalysts were successfully synthesized using a two-step hydrothermal method. In the first hydrothermal experiment ZnO/ZnWO₄ nanoneedle crystals were synthesized from NaWO₄ ·2H₂O and Zn(NO₃)₂ ·6H₂O, using polyacrylamide (PAM) as a template in a hydrothermal environment. Bi cations were then reduced by t-BuONa in a second hydrothermal experiment, adding nanoneedle ZnO/ZnWO₄. The catalysts were then characterized by powder X-ray diffraction (XRD), scanning electron microcopy (SEM), energy dispersive spectrometer (EDS) and UV-vis diffuse reflectance spectrum (DRS). The results show that by adding Bi nanoparticles, the composition of the mixture gradually changed from that of ZnO/ZnWO₄ to Bi/ZnWO₄. The nanoneedle Bi/ZnWO₄ samples displayed better UV light photocatalysis than the nanoneedle ZnO/ZnWO₄ samples. The optimum concentration of Bi was investigated using a photocatalytic experiment. A “blue shift” was observed when the molar ratio of Bi was increased.