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Nafion 112/polyaniline (Na/PANi) composite membranes were synthesized by chemical polymerization of aniline on the perfluorinated structure for use in direct methanol fuel cells as a solid electrolyte. The morphology and physicochemical properties of the composite membranes were analyzed by scanning electron microscopy (SEM), attenuation Fourier reflection infrared spectroscopy (FTIR-ATR), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the membranes were investigated by scanning electrochemical microscopy (SECM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results show that PANi-modified Nafion during 1 and 24 h decrease the methanol crossover by 78% and 89% and increase the proton conductivity by 17% and 2.6% respectively.

Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct methanol fuel cells. Here, a straightforward deposition method of polypyrrole deposition on Nafion has been achieved by chemical polymerization in an aqueous medium. The chemical polymerization has been carried out during 1 h and 24 h; thus, the effect of the polypyrrole coating has been studied toward the leakage of methanol by cyclic voltammetry. It was found that the diffusion of methanol has been reduced for at least to three decades in comparison to commercial Nafion. The effect of the polypyrrole (PPy) coating on transport properties such as water uptake, ion exchange capacity, and proton conductivity has been investigated. Scanning electrochemical microscopy (SECM) has been used to investigate quantitatively the membrane proton conductivity. A potentiometric tungsten microelectrode, positioned above the membrane, was used to monitor directly the diffusion of H+. The chemical and morphological characterization of PPy coating has been characterized by Fourier transform infrared FTIR–ATR spectroscopy, X-ray photoelectron (XPS), scanning electron microscope (SEM), and atomic force microscopy (AFM).

The electrochemical behavior of polypyrrole (PPy)-coated carbon steel (CS) was investigated in aqueous NaCl solution by scanning electrochemical microscopy. Oxygen concentration and pH were monitored by placing Pt and Sb microelectrodes, respectively, over the CS sample surfaces while soaking them in corrosion media. The PPy layer provided anodic protection, as well as a physical barrier, against the corrosive effect. The ratio of these properties was dependent on the thickness of the coating. Electrosynthesis of PPy/CS was achieved in an aqueous solution of sodium tartrate and pyrrole using cyclic voltammetric and galvanostatic techniques. The coatings were characterized by X-ray photoelectron spectroscopy and scanning electron microscopy. The doping rate calculated from XPS spectra was estimated at 15 %. The corrosion protective extent of the coating was tested in 3 % NaCl solution using three different techniques: linear polarization, open circuit potential, and electrochemical impedance spectroscopy. PPy offered significant protection against corrosion, with the coating resistance decreasing as immersion time increased.

The electrosynthesis of polypyrrole (PPy) on copper and brass (Cu–Zn alloy) electrodes was performed by anodic oxidation of pyrrole in a sodium tartrate (C4H4Na2O6 0.2 M) aqueous solution. The tartrate counter-ions slow the dissolution of the working electrode by leading to formation of a passivation layer on its surface, and pyrrole electropolymerization takes place. Strongly adherent and homogeneous polypyrrole films were electrodeposited on Cu and Cu–Zn alloy electrodes using different electrochemical techniques, such as potentiodynamic, galvanostatic and potentiostatic modes. The current densities of electropolymerization on brass are generally greater than those observed on copper. The corrosion behaviour of copper-coated electrodes, electrochemically modified by PPy films, was estimated by DC polarization and weight loss at different current densities in 0.1 M HCl solution. The synthesized polypyrrole films were characterised by several microscopic and spectroscopic techniques such as scanning electron microscopy, X-ray photo electron spectroscopy, Fourier transform infrared and Raman analysis. Galvanostatically deposited PPy films are shown to be an alternative to common black-nickel or black-chromium as a decorative top-coating.