Unexpected Redox Enhancement and Electrochemical Pseudo-capacitance Performance of Polyaniline/poly(vinyl alcohol) (PAn/PVA) Composite Films

We report significant improvement, though unexpected contrary to intuition, of the redox behaviour and electrochemical pseudo-capacitance of polyaniline (PAn) conducting polymer composited with non-conducting poly(vinyl alcohol) (PVA). Redox and film composition characterizations were carried out using a combination of in situ electrochemical and nanogravimentric techniques. Film structural changes due to the presence of PVA in the matrix of PAn have been studied with FT-IR and XRD as well as thermal analysis techniques such as TGA and DSC. The increase in PAn/PVA film redox responses compared to pure PAn film was observed to be a factor of ca. 2 while electrochemical capacitance enhancement was obtained to be ca. 40% increase (ca. 130 F g−1 for PAn/PVA composite film compared to ca. 94 F g−1 for PAn). These drastic improvements of composite film's redox behaviour were attributed to the increase in film chain-chain interactions due to the presence of multiple hydrogen bonding created by the introduction of PVA chain segments in the bulk of PAn film and thus enhancing the rate of film redox conversions. Redox enhancement was also associated to the increase in composite film's ion doping capacity.