Effect of iron doping concentration on the structure and photocatalytic activity of ZnO nanosheets under visible light irradiation

Abstract

Undoped and Fe-doped ZnO nanosheets have been successfully synthesized by hydrothermal method using zinc acetate as the source of  Zn²⁺, iron(III) nitrate as the doping source, urea as media to control the solution pH and polyethylene glycol as structure-directing agents. The obtained materials were characterized by means of XRD, TEM, BET, FT-IR and UV-Vis-DRS. The results show that ZnO has a hexagonal wurtzite structure and that the Fe³⁺ ions were well incorporated into the ZnO nanosheets crystal lattice. As the Fe/Zn molar ratios increased from 0.05% to 0.1% results in increased absorption in the visible region of the spectrum, a slightly decreased optical band gap and increased photocatalytic activity in comparison with the undoped ZnO. The photocatalytic activity was evaluated based on photodegradation of methylene blue (MB) in aqueous solutions under visible light irradiation. The optimum Fe doping at the molar ratios of Fe/Zn = 0.1% showed the highest photocatalytic activity and was 2.19 times higher than that of undoped ZnO. The kinetic studies showed the decomposition of MB followed pseudo first-order kinetics with the rate constant were determined k_app = 7.33×10^-2 min⁻¹.