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Influence of NafionTM and poly(vinylidene-fluoride) on capacitive properties of polyaniline/Ru-oxide composite

Hydrous Ru-oxide is one of the most important materials for electrochemical supercapacitors due to high electrochemical reversibility, high stability and high specific capacitance values [1]. However, electrochemical reactions giving rise to its high pseudocapacitance are limited to a rather thin surface layer of deposited film. It is therefore of high importance to improve utilization of Ru material and achieve higher gravimetric energy and power densities. Among various strategies for preparation of hydrous Ru-oxide electrode with enhanced capacitance, formation of different composite materials has already been attempted in the literature [2-3]. Such composites are synthesized in order to combine beneficial properties of hydrous Ru-oxide with advantages of other materials such as high surface area. Due to the extremely high surface area and charge storage capability, conducting polymers are promising candidates for composite formation. In this work, composite material was prepared as combination of ruthenium-oxide, poly(vinylidene-fluoride) (PVdF) or NafionTM and polyaniline. NafionTM or poly(vinylidene-fluoride) (PVdF) was introduced as a template for PANI film growth and for improving mechanical properties of electrodes. In the first step of preparation, hydrated ruthenium oxide particle suspension, in solution of (PVdF) in 1-methyl-2-pyrrolidone or in solution of NafionTM in alcohol, was casted onto glassy carbon electrode (GC). After solvent evaporation electropolymerisation of aniline was carried out within the formed composite from 0.1 mol dm-3 aniline solution in 0.5 mol dm-3 H2SO4. The electrochemical behavior of prepared composites was characterized in H2SO4 acid solution by cyclic voltammetry and electrochemical impedance spectroscopy techniques. The aim of this work was to study influence of polyaniline on specific charge increase and to determine optimal amount of polymer. Additionally, the influence of poly(vinylidene-fluoride) and NafionTM on the composite properties was evaluated. The results in Fig.1 and Fig. 2 demonstrate that for both composites addition of polyaniline results in the increase of charge. In the case of presence of NafionTM the increase in charge was observed only for small amounts of polyaniline whereas at higher loadings an irreversible deformation of cyclic voltammograms are observed (Fig. 2). Comparing the behavior of two composites with the same amount of Ru-oxide (1 mg), higher capacitive values were obtained for PVdF/Ru-oxide than for Nafion/TMRu-oxide.

Ru-oxide; polyaniline; supercapacitors; Nafion; poly(vinylidene-fluoride)

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