Electrocatalysis of the quinone/hydroquinone system by electrodes coated with substituted polyaniline

Polymer films derived from N-methylaniline (NMA), N(3-sulphopropyl)-aniline (NSPA), 2- and 3-methylanilines (2-MA and 3-MA), and 2,3-, 2,5- and 2,6-dimethylanilines (2,3-DMA, 2,5-DMA and 2,6-DMA), as well as of some copolymers, were obtained on a platinum electrode in acidic solution by potential cycling. Electrocatalytic properties of the resulting polymer coated electrodes towards the hydroquinone-benzoquinone redox couple were investigated. The following sequence of catalytic activity was found: poly(2-MA) much greater than polyNMA = copoly (2-MA + 3-MA) > copoly(NMA + NSPA) > polyNSPA much greater than poly(3-MA). With respect to the stability of catalytic effects observed at prolonged potential cycling, the following sequence can be drawn: poly(2-MA), polyNSPA much greater than copoly(2-MA + 3-MA) = poly(3-MA)> copoly(NMA + NSPA) > polyNMA, Thus, poly(2-MA) was found to be the most effective and stable electrocatalyst in the redox couple investigated. The polymers derived from dimethylanilines were found to inhibit this redox process.