Electrodeposition of binder-free polypyrrole on a three-dimensional flower-like nanosheet of manganese oxides containing pyrrole derivative for supercapacitor electrode

Abstract

A series of nanocomposite electrodes for supercapacitors were manufactured using a two-step electrochemical synthesis of manganese oxides and polypyrrole (PPy). Under reductive conditions, an aqueous mixture of manganese nitrate and pyrrole monomer was used to develop flower-like 3D nanosheets of manganese hydroxide containing pyrrole derivative directly on a stainless-steel mesh. The nanosheets were calcined to manganese oxides, and then, PPy was deposited on the nanosheets under oxidative conditions as a polarity inversion process. The PPy changed its morphology from nanoparticles to films via aggregation as the deposition time increased. The electrochemical performance of obtained nanocomposites electrode was characterized using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The specific capacitance of the nanocomposites exhibited nearly 3 times higher specific capacitance (825 F/g) than the manganese oxides without PPy (270 F/g). This improvement could be attributed to the synergetic effects of two components. The nanocomposite electrode exhibited high stability (86% and 99.3% cycle stability and columbic efficiency, respectively, after 2000 cycles) and a high rate capability (376 F/g at 100 mV/s).