Intrinsic defect enhanced photocatalytic activity of Gd3+ doped ZnO nanoparticles

Abstract

Gd-doped ZnO (GdxZn1-xO, where x = 0.00, 0.03, 0.06, 0.09 and x = 0.12) with rich oxygen vacancy defects was synthesized by co-precipitation method. The formation of hexagonal wurtzite structure of ZnO and Gd doped ZnO was confirmed by X-ray Diffraction (XRD). Energy Dispersive X-ray (EDX) analysis shows the presence of zinc, gadolinium, and oxygen in stoichiometric ratios. SEM images showed a mixed morphology of spindle and spherical particles upon doping. Optical band gap energy calculated from the UV–visible absorbance spectra of the samples was found to be ∼3.32 eV. Photoluminescence (PL) and Raman spectroscopy reveals the presence of various surface defects in the Gd doped samples with Gd0.06Zn0.94O possessing maximum oxygen vacancy/zinc interstitials related defects. Gd0.06Zn0.94O also exhibits the best photocatalytic activity towards the degradation of malachite green (MG) dye among the doped samples. Under the optimized conditions of Gd0.06Zn0.94O load = 0.35 g/L; dye concentration = 10 ppm and dye solution's pH = 10, degradation percentage increases from 96% in 3hrs. 30 min without optimization to 99% within 10 min of irradiation. Scavenging activity study revealed that electrons play major role in the photodegradation process. From the reusability study of the photocatalyst, the photodegradation percentage of the photocatalyst was found to decline gradually in the consecutive runs which needs to be overcome by a suitable solution.