Ordered Polypyrrole Nanowire Arrays Grown on a Carbon Cloth Substrate for a High-Performance Pseudocapacitor Electrode

Highly aligned nanoarchitecture arrays directly grown on conducting substrates open up a new direction to accelerate Faradaic reactions for charge storage as well as address "dead volume" limitations for high-performance pseudocapacitor electrodes. Here we reported the electrochemical fabrication of well-ordered polypyrrole (PPy) nanowire arrays (NWAs) on surfaces of carbon fibers in an untreated carbon cloth to construct hierarchical structures constituted by the three-dimensional conductive carbon fiber skeleton and the atop well-ordered electroactive polymer nanowires. The morphologies, wetting behaviors, and charge-storage performances of the polymer were investigated by scanning electron microscopy, transmission electron microscopy, contact-angle measurement, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The well-ordered PPy NWA electrode exhibited a high specific capacitance of 699 F/g at 1 A/g with excellent rate capability, and 92.4% and 81.5% of its capacitance could be retained at 10 and 20 A/g, respectively. An extremely high energy density of 164.07 Wh/kg could be achieved by the PPy NWAs at a power density of 0.65 kW/kg. It also displayed a quite high energy density of 133.79 Wh/kg at a high power density of 13 kW/kg. The assembled symmetric supercapacitor of PPy NWAs//PPy NWAs also exhibited excellent rate capability, and only 19% of its energy density decreased when the power density increased 20 times from 0.65 to 13 kW/kg.