Synthesis, surface characterization and electrochemical performance of ZnO @ activated carbon as a supercapacitor electrode material in acidic and alkaline electrolytes

Abstract

The chemical and surface modification of activated carbon (AC) through the incorporation of nanoparticles (NPs) is a simple and efficient strategy to enhance the charge transfer as well as the capacitance behavior of AC. Herein, ZnO-NPs were successfully attached at the surface of AC via one-step hydrothermal process to form ZnO-NPs@AC (ZAC). The introduced ZAC-material was studied by surface characterization techniques including transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) to investigate the morphological and chemical characteristics of ZAC. After that, ZAC was utilized as a working electrode (WE) material for supercapacitor in alkaline and acidic electrolytes. The specific capacitance (Cs) values of ZAC showed an enhanced performance as compared with that of the pristine AC. Moreover, the low series resistance and high Warburg co-efficient of ZAC as compared to those of the AC indicated the faster −OH diffusion inside the ZAC working electrode. Additionally, the phase angle of ZAC is closer to the ideal capacitor than that of AC. Overall, this study proved that ZnO-NPs can enhance the AC capacitance behavior through the easy chemical modification of AC.