PEDOT Nanotubes Electrochemically Synthesized on Flexible Substrates: Enhancement of Supercapacitive and Electrocatalytic Properties

PEDOT nanotubes were successfully electrodeposited onto stainless steel mesh electrodes in the presence of methyl orange template for the first time. It was found that the pH of the reaction medium is a key parameter to tune up the final morphology of the electrodeposited material. The modified electrodes were characterized by electrochemical, spectroscopic, and both scanning and transmission electron microscopy techniques. It was observed that the PEDOT nanotubes were formed all around the electrode in acidic conditions, while a globular morphology was verified in the synthesis in neutral medium. To better understand the mechanism of nanotube formation, the current–time transients obtained in the synthesis were fitted accordingly with a theoretical model, and the total current was deconvoluted into components that describe the polymer 3D growth and EDOT oxidation onto the PEDOT surface. The cyclic voltammetry of the modified electrodes exhibited an intense pseudocapacitive behavior, and their properties were also tested by galvanostatic charge/discharge cycles. The maximum specific capacitance obtained herein was 307.3 F g–1 at a current density of 0.8 A g–1, and a capacity retention of 77% was obtained after 2500 galvanostatic charge/discharge cycles, with no drastic changes in the capacitance when the electrode was folded or twisted. The PEDOT nanotubes were also tested for the electrocatalytic reduction of 2-nitrophenol isomer, which was evaluated by spectroelectrochemical method. The constant rate obtained (1.07 × 10–3 s–1) could be compared with works employing chemical catalysis, indicating that the nanotube morphology provides excellent eletrocatalytical properties, and the kinetic experiments were corroborated by the study of the interfacial electrochemical features by using electrochemical impedance spectroscopy experiments in an innovative methodology.