Novel green synthesis of ZnAl2O4 and ZnAl2O4/graphene nanocomposite and comparison of electrochemical hydrogen storage and Coulombic efficiency

In this experimental work, a green biosynthesize method was used to synthesis of ZnAl2O4 nanoparticles. To synthesis of the ZnAl2O4 spinel, beside the Zn2+ and Al3+ sources, olive leaf and green tea extracts were used as reagents. The Electrochemical hydrogen storage performance of ZnAl2O4 synthesized via olive leaf and green tea extracts were compared via chronopotentiometry method in aqueous KOH electrolyte, for first time. The hydrogen storage capacity of ZnAl2O4 spinel enhanced by synthesize nanocomposite of ZnAl2O4 with graphene nanosheet. Also, different analysis were served to study the products structure, composition and morphologies. The porous structure of samples was investigated by BET analysis. X-ray diffraction (XRD) patterns were used to investigate the phase and purity of the synthesized nanostructures. Energy dispersive X-ray spectroscopy (EDS) was used to obtaine the chemical compositions of the nanostructures and also to approve the XRD results. To further study the chemical composition of the products, Fourier transform infrared (FT-IR) analysis was served. The products size and morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. The results showed that the reagents specially olive leaf and green tea extracts had significant role in product size and morphology. (C) 2018 Elsevier Ltd. All rights reserved.