Influence of fluorine on structure, morphology, optical and photocatalytic properties of ZnWO4 Nanostructures

Abstract

We report on the synthesis of Fluorine (F) doped-ZnWO4 photocatalysts and the influence of F-doping on their structure, morphology, optical and photocatalytic properties. A two-step process was used to produce F-doped ZnWO4 photocatalysts. The quality of synthesized materials was characterized using different analytical methods, such as X-ray diffraction analysis, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectra (FTIR), as well as photoluminescence (PL) measurement. It was found that the photocatalyst morphology and band gap energy strongly depend on the F-doping concentration. The band gap energy of the photocatalysts decreased when increasing F-doping concentration, and reached a lowest value at a concentration of 4 mol%, and then increased thereafter. At 4 mol% of F-doping, nanowires were formed with approximately 1 μm in length and 50 nm in diameter. On the contrary, others F-doped ZnWO4 samples were obtained in the shape of nanorods or a mixture of nanorods and granular particles. Moreover, it was demonstrated that F-doped ZnWO4 enhanced photocatalytic activity by a factor of three, as compared to that of un-doped ZnWO4. This enhancement can be explained by the nanowire shape of synthesized F-doped ZnWO4, its narrow band gap energy and the small recombination rate of photogenerated electron-hole pairs, which was indirectly proved by PL spectra.