Direct electrodeposition of imidazole modified poly(pyrrole) copolymers : synthesis, characterization and supercapacitive properties

Altres ajuts: Beatriu de Pinós (BP-DGR-2013)In this manuscript we report the direct electrosynthesis of a new conducting copolymer based on the incorporation of imidazole molecules within the polypyrrole chain. Different proportions of the monomers were tested during the direct electropolymerization of the copolymer. The resulting materials were characterized by electrochemical and spectroscopic techniques (Raman and XPS) and a mechanism of polymerization is proposed. Our findings showed that imidazole acts as an inhibitor of the polymerization process, decreasing the overall number of actives sites for the polymerization on the electrode surface producing a polymeric morphology very different compared with pure polypyrrole, as observed by Scanning Electron Microscopy images and corroborated by Electrochemical Impedance Spectroscopy. This behavior significantly affects the supercapacitive performance of the resulting p(Py-IMZ) modified electrodes where the specific capacitance of the material increased from 122 to 201 Fg (64%) at 10 mV s. Furthermore, a unique pseudo-capacitive behavior described herein emphasizes the role of the imidazole as inductor of the morphology and co-monomer in the unique electrochemical signature of the material. The results suggest that the incorporation of IMZ increases the specific capacitance of PPy electrode by around 64%

Interfacial Characterization of Polypyrrole/AuNP Composites towards Electrocatalysis of Ascorbic Acid Oxidation

Polypyrrole (PPy) is an interesting conducting polymer due to its good environmental stability, high conductivity, and biocompatibility. The association between PPy and metallic nanoparticles has been widely studied since it enhances electrochemical properties. In this context, gold ions are reduced to gold nanoparticles (AuNPs) directly on the polymer surface as PPy can be oxidized to an overoxidized state. This work proposes the PPy electrochemical synthesis followed by the direct reduction of gold on its surface in a fast reaction. The modified electrodes were characterized by electronic microscopic and infrared spectroscopy. The effect of reduction time on the electrochemical properties was evaluated by the electrocatalytic properties of the obtained material from the oxidation of ascorbic acid (AA) and electrochemical impedance spectroscopy studies. The presence of AuNPs improved the AA electrocatalysis by reducing oxidation potential and lowering charge transfer resistance. EIS data were fitted using a transmission line model. The results indicated an increase in the electronic transport of the polymeric film in the presence of AuNPs. However, PPy overoxidation occurs when the AuNPs’ deposition is higher than 30 s. In PPy/AuNPs 15 s, smaller and less agglomerated particles were formed with fewer PPy overoxidized, confirming the observed electrocatalytic behavior