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Supercapacitors Based on Polymeric Dioxypyrroles and Single Walled Carbon Nanotubes
This paper reports a novel supercapacitor electrode design
based on polyÂ(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/cm<sup>2</sup> and 16.4
mF/cm<sup>2</sup>, 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/cm<sup>2</sup>, whereas a significantly
greater value of 8.8 mF/cm<sup>2</sup> 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/cm<sup>2</sup>) after 32 700 charge/discharge cycles,
which was still 38% larger than the initial capacitance of the gold
electrode devices