Investigation on the g-C3N4 encapsulated ZnO nanorods heterojunction coupled with GO for effective photocatalytic activity under visible light irradiation

Abstract

The present work reports on a novel ternary nanocomposite of ZnO rods encapsulated by graphitic like carbon nitride (g-C3N4) and coupled with graphene oxide (GO) prepared by ultrasonication assisted hydrothermal method which provides enhanced photocatalytic activity and stability. Field emission scanning electron microscopy analysis showed that the surface morphology of ZnO, g-C3N4 (prepared by heating method) and the GO contains nanorods structures, sheet like structures and sheets with porous structures respectively. Formation of rod like structures of ZnO and thin sheet like structures of g-C3N4 were observed from transmission electron microscopy analysis. Transmission electron microscopy analysis of g-C3N4 (6 wt%)/ZnO nanocomposites showed that ZnO nanorods are encapsulated by the thin sheets of g-C3N4 and g-C3N4(6 wt%)/ZnO/GO (30 mg) ternary nanocomposites contains porous structures of GO. The optical band gap of ZnO nanoparticles was shifted from 3.08 eV to 2.85 eV for g-C3N4(6 wt%)/ZnO/GO(30 mg) ternary nanocomposites. Under visible light irradiation the ZnO nanorods and g-C3N4 (6 wt%)/ZnO showed photodegradation efficiency of ∼21% and 90% respectively for 120 min whereas g-C3N4 (6 wt%)/ZnO/GO(30 mg) showed about 99% photodegradation efficiency in a time period of 14 min. The recycle process carried out for g-C3N4(6 wt%)/ZnO/GO(30 mg) composites up to five cycles showed 91.5% of photodegradation in the fifth cycle for a time period of 14 min. Total Organic Carbon (TOC) analysis shows removal of carbon content 83% in 28 min. The Gas Chromatography-Mass Spectroscopy analysis shows the intermediate products of 1,2 benzenedicarboxylic acid and phthalic acid during the RhB dye photodegradation process. The radical trapping experiment reveals that the photo-induced holes (h+) are one of the main reactive species involved in the degradation of the RhB.