Supercapacitors Based on Polymeric Dioxypyrroles and Single Walled Carbon Nanotubes

Abstract

This paper reports a novel supercapacitor electrode design based on poly(3,4-propylenedioxypyrrole) (PProDOP) electropolymerized onto thin films of single walled carbon nanotubes (SWNTs) on glass substrates. This permits the electropolymerization of thicker PProDOP films than can be deposited onto flat gold-coated Kapton electrodes and a correspondingly greater capacitance per unit area. A pyrene functionalized polyfluorene, designated Sticky-PF, was designed and used as an effective monolayer interfacial adhesion modifier between the SWNT films and PProDOP via noncovalent self-assembly onto the SWNT film surfaces before polymer electrodeposition. The thickness of the electrodeposited PProDOP was found to be self-limiting at thicknesses characteristic of each substrate electrode. Optimized areal capacitance values for PProDOP on flat gold and Sticky-PF coated SWNT films were measured to be 8.1 mF/cm2 and 16.4 mF/cm2, respectively, with the twofold enhancement due to the thicker films possible on the SWNT electrode. The specific capacitance of PProDOP on gold and Sticky-PF|SWNT film substrates were found to be similar at 141 F/g and 122 F/g, respectively, indicating the capacitance to be due to the electroactive polymer. The areal capacitance values of the corresponding supercapacitor devices constructed with Au/Kapton substrates was 3.2 mF/cm2, whereas a significantly greater value of 8.8 mF/cm2 was measured for the Sticky-PF|SWNT film substrates. The supercapacitors prepared using the Au/Kapton substrates were highly stable, retaining 80% of their electroactivity after 32 700 nonstop charge/discharge cycles (100% depth of discharge). Supercapacitors made using the Sticky-PF|SWNT substrates showed a steady loss of capacitance to about 57% of the original value (to 5.0 mF/cm2) after 32 700 charge/discharge cycles, which was still 38% larger than the initial capacitance of the gold electrode devices.