Copper and zinc oxide anchored silica microsphere: A superior pseudocapacitive positive electrode for aqueous supercapacitor applications

Abstract

Synthesis of metal and metal oxides with silica (SiO2) for catalyst purpose is an important topic in energy application. However, preparation of the silica-based catalyst with controlled size is still limited, leading to the loss of the catalytic activity and reusability performance. Improving conductivity and surface properties of SiO2 by decorating of suitable metal/metal oxides is a novel route to utilise the earth abundant silica for diverse application. Herein, we report highly uniform copper (Cu) and zinc oxide (ZnO) anchored SiO2 synthesised by facile sol-gel method. The crystalline structure of SiO2 (amorphous), Cu (cubic) and ZnO (hexagonal) were confirmed by X-ray diffraction (XRD). Chemical composition and the oxidation state of the elements present in the composites were confirmed by X-ray photoelectron spectroscopy (XPS). Microstructural and compositional information of the silica-based nanoparticle were investigated using Laser Raman, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. The size of the anchored tiny nanoparticles (Cu and ZnO) on SiO2 surface was determined from the FESEM and TEM analysis. The charge-discharge result showed high specific capacitance of 423 F g−1 and 227.5 F g−1 for SiO2–Cu and SiO2–ZnO at 4 mA g−1, respectively. It was clearly observed that the silica-based composites with improved physical and electrochemical performances will be considered as promising candidate for achieving high electrical energy storage capacitor as a positive electrode.