Structural and XPS studies of polyhedral europium doped gadolinium orthovanadate (Eu3+:GdVO4) nanocatalyst for augmented photodegradation against Congo-red

Abstract

The present work demonstrates structural, valence band mapping (VBM) and photocatalytic activity of Eu3+ doped orthovanadate (GdVO4) nanosystem against an azo-dye, Congo-red. As evident from x-ray diffraction (XRD) studies, the nanosystem synthesized via a solid-state cum sintering route exhibited zircon-type crystal structure with space group I 41/amd. Imaging through transmission electron microscopy (TEM) has revealed polyhedral nanoaggregates, which are of polycrystalline nature. Introduction of Eu3+ into the host GdVO4 was substantiated from the energy dispersive x-ray (EDX) spectra, x-ray photoelectron spectra (XPS) and considering inclusion of dopants to binding energy correspondence in the VBM spectra. In this study, the azo-dye Congo-red has been opted as the target dye for photodegradation. After UV light illumination, Eu3+:GdVO4 nano-catalyst could degrade the organic dye quite effeciently (up to 91.8%), and offering a rate constant nearly doubled as compared with its undoped counterpart. The dopant ions being associated with the new localized states enabling promotion of additional photoexcited carriers taking advantage of the incident UV exposure. Structural, XPS, and optical studies of the rare-earth vanadate nano-systems as well as their photocatalytic activity would provide new insights to resolve existing concerns, viz., removal of organic contaminants, and environmentally harmful dyes and to carry multi-functional scope for industrial relevance. Moreover, such systems may have immense potential for displaying select emission response as well as photocatalysis even though both processes are mediated via opposite effects.