Green synthesis and characterization of Ag-doped ZnO nanofibers for photodegradation of MB, RhB and MO dye molecules

Abstract

In this study, silver (Ag)-doped zinc oxide (ZnO) nanofiber photocatalysts were synthesized using electrospinning method. To understand the effect of Ag doping on the photocatalytic efficiencies, ZnO nanofibers were prepared with different loading ratios (0, 0.3, 0.5, 1.0 at.% Ag). The synthesized nanofibers were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectroscopy and photoluminescence (PL) spectroscopy techniques. The photocatalytic performances of the fibers were first evaluated by measuring the photodegradation of methylene blue (MB) under the UV light irradiation. It was found that the amount of dopant ions has a crucial effect on the degradation process of MB. The results show that 0.5 at.% Ag dopant dosage is the ideal to achieve maximum catalytic efficiency against MB dye molecules with nearly complete decolorization just after 75 min UV light irradiation. During the degradation process, the substitutional incorporation of dopant ions provides better photocatalytic efficiency due to forming higher number of charge carriers and so delaying the recombination process. The recycling experiments for MB dye degradation were performed to determine the conservation of the catalytic efficiency and chemical stability of the nanofibers. To compare the photocatalytic efficiency of nanofibers against different dye molecules, the degradation performance of 0.5 at.% Ag-doped ZnO nanofibers was also experimentally examined by the measuring the photocatalytic degradation rates of various harmful organic dyes such as Rhodamine B (RhB) and methylene orange (MO) under the UV light irradiation. It was found that the photodegradation rates of RhB and MO synthetic dye solutions are determined as follows: similar to 66% and similar to 51% decomposition after 120 min UV light irradiation, respectively. A possible mechanism for the improvement of the photocatalytic performance of ZnO nanofibers by Ag loading is proposed.