Investigate the effect of silica on improvement electrochemical storage of hydrogen in ZnAl2O4 spinel

Abstract

In this work, different morphologies of pure ZnAl2O4 nanostructures and ZnAl2O4/SiO2 nanocomposites were successfully synthesized via a simple co-precipitation method. Two green reagents namely green tea and olive leaf extracts were used to the synthesis of these nanostructures. The products were examined by different analysis such as X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). It was found all samples have pure structures and there are no impurities in the products. The porosity of samples was investigated by BET analysis. The results showed that the reagents have a significant role in the product size and morphology and by changing the extracts, they growth in different directions. Also, it was found that the products are composed of very tiny particles and due to their high active surface area, they aggregated together and some big particles are obtained. The electrochemical hydrogen storage performance of ZnAl2O4 and ZnAl2O4/SiO2 nanocomposite were investigated by the galvanostatic charge-discharge method in 6 M KOH aqueous medium under 1 mA current. The discharge time of ZnAl2O4, ZnAl2O4/SiO2 (synthesized using green tea extract), ZnAl2O4, ZnAl2O4/SiO2 (synthesized using olive leaf extract) is 1750, 2800, 3900 and 5000s, respectively. EIS indicates that the resistance of CU-foam electrodes increases with the addition of samples. The ZnAl2O4 and ZnAl2O4/SiO2 is a good candidate for hydrogen storage due to the electrochemical hydrogen storage performance suitable. The green synthesis and hydrogen storage are very useful for prevent environmental pollution that were used in this work.