Influence of Zn doping on the electrochemical capacitor behavior of MnO2 nanocrystals

Abstract

Herein, we suggest a simple chemical precipitation method for the preparation of bare and different levels of Zn doped MnO₂ nanoparticles as electrodes for supercapacitors. The structure and chemical composition of the products were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. The morphologies of the undoped and doped products were analyzed by a scanning electron microscope (SEM) and a field emission transmission electron microscope (FE-TEM). The surface areas and pore volumes of the products were determined from N₂ adsorption–desorption isotherm curves and the results reveal that MnO₂ doped with Zn yields a smaller particle size, higher specific surface area, and a larger pore volume than those of pure MnO₂. The capacitance behavior of the products was analyzed by cyclic voltammetry, galvanostatic charge–discharge and impedance spectroscopy. The results of the capacitance behavior reveal the improved capacitance performance for MnO₂ on Zn doping. Especially, among the doped products, MnO₂ doped with 0.125 M Zn gives the high specific capacitance of 620 F g⁻¹ at 10 mV s⁻¹. The present work may open up a new path for the improvement of pseudocapacitance behavior of manganese oxide by Zn doping.