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

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 N-2 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.