Contact electro catalysis driven degradation of malachite green dye by RGO/ZnO nanohybrid

Abstract

This work demonstrates the potential of reduced graphene/zinc oxide (RGO/ZnO) nanohybrid for the degradation of malachite green dye (MG) via involving the mechanochemistry contact electro catalysis (CEC) approach through electronic transfer. Dielectric and piezoelectric RGO/ZnO nanohybrid in contact with aqueous medium offers electron transfer via direct catalytic reaction at solid-liquid interface which promotes CEC process than that of conventional photocatalysis. RGO/ZnO nanohybrid is prepared via ultrafast microwave irradiation method in 60 s using Mangifera indica leaves extract as a green reducing agent. The prepared RGO/ZnO nanohybrid is characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and UV–Visible (UV–Vis) spectroscopy. XRD analysis reveals the formation of pure ZnO with wurtzite hexagonal phase and signature reflection of the RGO. Raman, FTIR and UV–Vis spectroscopy results confirm the presence of bands corresponding to ZnO and RGO and hence the formation of RGO/ZnO nanohybrid without any impurity phase. Field emission-scanning electron microscopy (FE-SEM) reveals the growth of spherical shaped ZnO nanoparticles over the RGO matrix. The average particle size of ZnO nanoparticles is ⁓ 9.2 nm. Catalytic properties of RGO/ZnO nanohybrid is investigated by using 10 mg and 20 mg dosage in aqueous solution of MG. About 85.72 % degradation efficiency for MG in 60 min is achieved by using 20 mg RGO/ZnO nanohybrid via sonication through CEC process. Probably, contact electrolysis at ZnO-water interface induces electronic exchange and generation of free radicals to degrade the dye molecules. Reaction kinetics analysis reveals the suitability of the pseudo first-order kinetics for dye degradation and reusability of RGO/ZnO nanohybrid confirms its excellent stability up to three cycles with 60 % degradation ability. This research establishes RGO/ZnO nanohybrid as highly promising catalytic agents for wastewater treatment and hazard free CEC approach.