Preparation and Electrochemical Characterization of Polyaniline/Carbon Fiber Binary Composite Film Obtained with Carbon Fiber Treated at Different Temperatures

Introduction

Recently a great attention has been paid to based conducting-polymers system whose interests are related with the research scientific and technological application. These materials have a broad range of properties and applications which enables the opportunity to obtain a wide variety of promising new materials. Polyaniline (PAni) is one of the most investigated and commercialized conducting polymers because of its rapid and reversibly cycled between the conductive and the insulating states, associated with good stability, facility of preparation and the monomer low cost.

The results of synthesis and characterization of binary composites produced from carbon fiber (CF) and polyaniline (PAni) are presented and discussed. In this work,  it was used CF treated at different temperatures (1000 ºC, 1500 ºC and 2000ºC) to obtain binary composites. The composites were characterized by Scanning Electron Microscopy (SEM) and Raman Scattering Spectroscopy techniques to evaluate morphological and structural properties. The electrochemical characterization of the electrodes was studied by Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, and Charge/Discharge tests.

Experimental Parte

The carbon fibers treated at different temperatures
(1000 ºC, 1500 ºC and 2000 ºC) were cut in size 1 cm² and weighed. For each synthesis were produced eight samples, simultaneously. The fibers were fixed in a platinum wire and placed in a solution containing distilled aniline (12.6 mmol L^-1) and 1.0 mol L^-1 HCl,
3.0 mol L^-1 NaCl at -10 ºC. Another solution containing 1.0 mol L^-1 HCl, 3.0 mol L^-1 NaCl and 0.03 mol L^-1 ammonium persulfate, (NH₄)₂S₂O₈, was added to the aniline solution at deposition time of the 60 min at -10 ºC with vigorous stirring. The morphology of the composites was evaluated by Scanning Electron Microscopy. Raman's spectra were recorded using a micro - Raman scattering spectroscopy. The electrochemical characterization of the electrodes was studied by Electrochemical Impedance Spectroscopy (EIE), Cyclic Voltammetry (CV), and Charge/Discharge tests. All measurements have been performed in 1.0 mol L^-1 H₂SO₄solution.

Results and discussion

SEM images figure 1(a-c) exhibit the carbon fibers well dispersed and enwrapped uniformly with PAni. This suggests that the interaction between polymer molecules and CFs overcomes the Van der Waals interaction between CFs, with the effective interaction between the π- bonds in the aromatic ring of the polyaniline besides the CF should strongly facilitate the charge-transfer reaction between the two components. In these composites, CFs can offer a good mechanical support to PAni and also ensure the electronic conduction in the composite electrode. The Raman spectra showed are presented in Fig 2. The characteristic C-N⁺ stretching vibration bands of the radical cations are observed between 1319 cm^-1 and 1340 cm^-1 related to the number of charge carriers. This band is not very evident in PAni powder. The fact that CF to form a frame for the polymer, may explain the synergy effect between the two components of the PAni/CF composite, which allowed PAni present in the composite showed higher number of charge carriers.The Figure 3 shows the CV curves for all PAni/FC electrodes that are characterized by rectangle-like shape and symmetric response of ideal capacitive behavior.The CF is a perfect support for PAni giving excellent enhancement of capacitance values for the PAni/CF composite.

Conclusion

In this work, we presented a PAni/CF composite which was synthesized by chemical polymerization. The high surface area and porous nature of the PAni/CF composite promoted a significantly better performance in terms of capacitance specific and electrochemical reversibility than that of the conventional PAni films

Acknowledgments

This work was supported by CNPq-170141/2014-4.