A\nNanofibrous Polypyrrole Membrane with an Ultrahigh\nAreal Specific Capacitance and Improved Energy and Power Densities

For conductive polymers\nto be competitive with carbon-based electrode\nmaterials, it is critical to increase their surface area and electroactivity.\nIn this work, a thick nanofibrous polypyrrole (PPy) membrane with\ncommunicating interfiber spaces was prepared through one-pot interfacial\npolymerization for the first time. The electrochemical properties\nand conductivity of the membrane were studied with cyclic voltammetry,\nelectrochemical impedance spectroscopy, and a four-point probe. Its\nmorphology, chemistry, and thermostability were evaluated by scanning\nelectron microscopy, X-ray photoelectron spectroscopy, Fourier transform\ninfrared spectroscopy, and thermogravimetric analysis. The areal specific\ncapacitances measured between 0.0 and 0.8 V at 1 mA/cm<sup>2</sup> were 19179, 13264, 7238, and 4458 mF/cm<sup>2</sup> for the membranes\ndoped with docusate sodium (AOT), camphor-10-sulfonic acid (β)\n(CSA), Cl<sup>–</sup>, and poly(sodium 4-styrenesulfonate)\n(PSS), respectively. The capacity retentions after 1000 cycles were\n83, 74, 67, and 61% for the AOT-, CSA-, PSS-, and Cl<sup>–</sup>-doped membranes, respectively. The Coulombic efficiency was above\n99% for all of the membranes. They showed energy densities of 1.7,\n1.2, 0.7, and 0.4 mWh/cm<sup>2</sup> and power densities of 0.61,\n0.75, 0.66, and 0.62 mW/cm<sup>2</sup> for the AOT-, CSA-, Cl<sup>–</sup>-, and PSS-doped membranes, respectively. The ultrahigh\nareal specific capacitance of PPy-AOT is due to its nanofibrous structure.\nA mechanism has been proposed to explain how this structure is formed\nbased on the role of AOT as the surfactant. This nanofibrous PPy membrane\nis easy to prepare and metal-free and offers a very high areal specific\ncapacitance, making it an excellent candidate to construct electrodes\nin pseudosupercapacitors.