▎ 摘　　要

One of the famous blue pigments is cobalt aluminate which has a normal spinel that in this work has been synthesized with thermal decomposition technique via the help of olive leaf extract as a precipitation agent. Furthermore, CoAl2O4/SiO2, CoAl2O4/TiO2 and CoAl2O4/graphene nanocomposites were prepared besides the pure one. To investigate the structure and composition of products, X-ray diffraction (XRD) pattern and Fourier transform infrared (FT-IR) analysis were served. Also, the morphologies of products were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the effect of different nucleation and growth conditions of the products were investigated. The hydrogen storage ability of the pure CoAl2O4 nanostructures was investigated and to increase the hydrogen storage capacity, different CoAl2O4 nanocomposites were prepared and studied. The maximum discharge capacity and Coulombic efficiencies are 2800 mAh/g and 62% that related to CoAl2O4/TiO2 composition and CoAl2O4, respectively. (c) 2020 Elsevier B.V. All rights reserved.