Synthesis,characterization, and transport properties of Nafion-polypyrrole membrane for direct methanol fuel cell (DMFC) application

Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct...     

A combined experimental and DFT investigation of the adsorption of humic acid by-products on polypyrrole

This study sheds light on the removal of humic acid by-products (trimellitic and pyromellitic acids; TMA and PMA, respectively) from aqueous solution using conducting polypyrrole (PPy) as an effective adsorbent. The effects of experimental factors including contact time, solution pH, initial concentration, adsorbent dose, and temperature were systematically investigated. The pseudo-second-order kinetic model provides the best correlation with adsorption experimental data. The equilibrium adsorption was well described by the Langmuir model with maximum mono-layer adsorption capacities of 47.62 and 71.43?mg?g^?1 for TMA and PMA, respectively. The analysis of thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. In addition, we investigated the adsorption mechanism using the density functional theory (DFT) calculations. The TMA and PMA were physisorbed on the PPy surface through the formation of hydrogen bonds between carboxylic groups of adsorbate molecules and the amino group of the adsorbent. The calculated theoretical data were in good agreement with experiments.     

Polypyrrole films electrosynthesized on stainless steel grid from saccharinate aqueous solution and its behaviour toward acetone vapor

The electrochemical behaviour of stainless steel electrode in 0.1 M sodium saccharinate solution in the absence and the presence of the monomer were investigated using several electrochemical techniques such as cyclic voltammetry, galvanostatic and potentiostatic. The XPS analysis was used to study the elementary composition of the obtained polymer and to estimate the doping level of the PPy obtained under this electrolytic conditions. Moreover, the characterization of the coating was achieved by SEM, IR and Raman. In this context, samples of PPy in oxidized and reduced state synthesized galvanostatically on stainless steel grid were used to investigate the behaviour of the polymer toward acetone vapor.     

X-ray photoelectron and in situ and ex situ resonance Raman spectroscopic investigations of polythiophene overoxidation

Polythiophene films have been electrochemically synthesized on platinum electrodes by anodic oxidation of thiophene in CH₃CN-LiClO₄ organic solution, then galvanostatically polarized in the same but monomer-free electrolytic medium to obtain the reduced, oxidized, and overoxidized states of the polymer. X-ray photoelectron spectroscopy (XPS) measurements were performed to investigate the changes within the chemical composition accompanying the overoxidation of the polythiophene (PT) film and connected to degradation mechanisms reported in the literature. Ex situ resonance Raman spectroscopy (RRS) studies of the three oxidation states, with red and near-infrared excitation laser lines, lead to complementary insights about the degradation process of this polymer. Particularly, marked modifications of the positions, widths, and relative intensities of the Raman bands are attributed to structural transformations and the appearance of defects in the polymer chains. Moreover, in situ RRS experiments, during the gradual transition between the reduced and overoxidized states, allow to determine the electrochemical stability threshold of the PT. In the reversibility domain, the quinoid to aromatic intensity ratio of the ring C=C symmetric stretching obeys a Nernst-like equation when the applied potential to the PT/Pt working electrode is varied.     

Application of Surface‐Enhanced Raman Scattering for ex Situ and in Situ Investigations of Polythiophene Derivatives

Polythiophene derivative films have been synthesized on electrochemically roughened silver, gold, and copper electrodes by anodic oxidation of the corresponding monomers. Surface‐enhanced Raman scattering (SERS) analyses of these coatings led to high‐quality spectra with high signal‐to‐noise ratios. In contrast with platinum, the use of SERS‐active metals allowed the observation of important changes in the positions, widths, and relative intensities of the Raman bands during the polymer doping‐dedoping process. In situ SERS investigations revealed that the modifications in the spectral features, when the polymer oxidation degree is progressively increased, are due to a transition from the aromatic to the quinoid structure and to an increase of structural defects along the polymer chains. Moreover, in the case of soluble polyalkylthiophene films, SERS analyses were also carried out using colloidal silver solutions. Despite the very low polymer concentration and the mild experimental conditions used in these experiments, a large amplification of the Raman signal took place. Two other methods for obtaining polybithiophene–silver composite films are reported. In these cases, thanks to the silver particles, the polymer displays a SERS effect, which greatly improves the signal‐to‐noise ratio of the Raman spectra, thus allowing a much better vibrational analysis of both doped and undoped states.     

Electrochemically roughened silver surface versus fractal leaf-shaped silver crystals for surface-enhanced Raman scattering investigation of polypyrrole

Journal of Solid State Electrochemistry - In surface-enhanced Raman scattering (SERS) analyses, the surface condition of the metal substrate plays a decisive role in the quality of the recorded...     

Analyses of scanning electrochemical microscopy and electrochemical impedance spectroscopy in direct methanol fuel cells: permeability resistance and proton conductivity of polyaniline modified membrane

Journal of Solid State Electrochemistry - Nafion 112/polyaniline (Na/PANi) composite membranes were synthesized by chemical polymerization of aniline on the perfluorinated structure for use in...     

Study of congo red adsorption on the polyaniline and polypyrrole

Polyaniline (PANI) and polypyrrole (PPY) were synthesized via in situ chemical oxidative polymerization and are used as adsorbents for removal of Congo Red (CR) dye from aqueous solution. The effects of various experimental parameters including pH of the solution, contact time, initial concentration, adsorbent dosage, and temperature on adsorption of CR by PANI and PPY were systematically investigated. The experimental results showed that the adsorption efficiency was increased with contact time and adsorbent dosage. The maximum removal efficiency was found after 45 minutes of solid/liquid contact with adsorbent doses of 0.4 and 1.73?g/L for PANI and PPY, respectively. The kinetic data were best fitted by the pseudo-second-order model. The adsorption equilibrium results were well fitted by the Langmuir isotherm model. These results suggest that the PANI and PPY can be used as alternative adsorbents for the treatment of wastewaters containing dyes.     

Different electrochemical techniques for the electrosynthesis of poly methylene blue in sodium saccharin aqueous medium

Journal of Solid State Electrochemistry - The present work describes the electropolymerization of methylene blue (MB) on transparent fluorine-doped tin oxide (FTO) from an aqueous solution of...