Electrochemical Synthesis of Mg-doped ZnO Nanotapers as Photocatalyst for Degradation of Bisphenol under Solar Light Irradiation

This paper released electrochemical synthesis of Mg doped ZnO nanotapers for degradation of bisphenol A (BPA) as toxic aquatic pollutant under UV and visible light irradiations. The pure and Mg-doped ZnO nanotapers photo-catalysts were prepared through an electrical field assisted method. The morphological, structural and optical properties of samples were characterized through the SEM,XRD and UV-Vis absorption spectra, respectively. The morphological and structural studies exhibited that the high density of pure and doped ZnO nanostructures were grown in vertically aligned taper-like shape and hexagonal wurtzite structures. Moreover, the doping process led to creation of the cubic MgO structure in ZnO nanotaper with (111) and (220) planes. The optical characterizations showed that the higher absorption peak was observed for doped samples due to the creation of oxygen deficiency and defects in grain structure of film. The Eg values were obtained 3.48 eV and 3.09 eV for pure ZnO and Mg-doped ZnO nanotapers films, respectively. The electrochemical studies by CV and EIS techniques showed the improvement of specific capacitance of electric double layer and film’s conductivity by Mg doping into ZnO matrix. The photocatalytic measurements displayed that the PBA degradation efficiencies were of 64.19 % and 100% for pure ZnO and Mg-doped ZnO nanotaper photo-catalysts for 70 minutes under UV irradiation, respectively. Therefore, the degradation efficiency of ZnO nanotapers was significantly improved by Mg doping. Furthermore, the PBA degradation efficiencies were 43.40 % and 100 % for pure and doped samples after 60 minutes under visible irradiation which indicates promotion of the degradation rate for Mg-doped ZnO nanotapers in visible irradiation. Eg value was decreased for doped samples due to the presence of Mg2+ inside the Zn2+ sites of the ZnO lattice which improve the charge separation. As a result, Mg-doped ZnO nanotapers film not only photo-excited in the UV region but also its photocatalytic activity was delayed in the visible region.