LAUSR

Abstract A pseudocapacitive electrode based on mesoporous manganese dioxide (MnO2) was fabricated via the anodic pulse electrodeposition method. Pulse current (PC) has many parameters that affect the physicochemical and electrochemical properties of the material. PC parameters are generally divided into independent and dependent types. Independent pulse parameters consist of the time of applying current (ton), interval time with zero current (toff), and peak current density (Ip). Dependent pulse parameters include duty cycle (θ), frequency (f), and average current density (Ia). In this work, the changes of two independent parameters (ton and toff) at the constant Ip = 2 mA cm-2 on the anodic pulse electrodeposition of MnO2 were investigated, which also caused changes in the independent parameters. The effects of changes in pulse parameters on physicochemical properties of MnO2 were studied by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction technique, and nitrogen gas adsorption-desorption isotherms. Cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy techniques were applied to investigate the electrochemical behavior of the prepared MnO2 samples. The pulse conditions in the best sample were ton = 10 ms, toff = 30 ms, θ = 25% and f = 25 Hz. This sample was the body-centered tetragonal phase of α-MnO2 with a significant specific surface area of 154.03 m2 g-1. The specific capacitances of the optimal sample were 526.44 and 120 F g-1 at the current densities of 0.5 and 10 A g-1, respectively. The two-electrode symmetric supercapacitor cell assembled using the best sample was showed the specific capacitance of 300.63 F g-1 at a current density of 0.5 A g-1. The capacitance maintenance of the fabricated device was 87.10% after 5000 cycles at a current density of 4 A g-1, which confirmed the good cyclic stability of this symmetric supercapacitor. The maximum energy and power densities were 81.84 Wh kg-1 and 17.49 kW kg-1, respectively, which indicated the good pseudocapacitive performance of the MnO2-based symmetric supercapacitor.