Electrocatalysis of the hydroquinone/benzoquinone redox couple at platinum electrodes covered by a thin film of poly(3,4-ethylenedioxythiophene)

Abstract

The hydroquinone/benzoquinone (HQ/BQ) redox reaction is studied on platinum electrodes coated by poly(3,4-ethylenedioxythiophene) (PEDOT) thin films using cyclic voltammetry and chronocoulometry. It was found that HQ is weakly adsorbed on PEDOT and that the HQ/BQ redox reaction is well described by a reversible diffusion-governed charge transfer on platinum electrodes coated by a thin film of PEDOT and in the presence of very low HQ concentration, indicating that the modification of PEDOT on Pt can greatly accelerate the electron transfer rate and that PEDOT seems to be the best electrocatalyst for this reaction reported until know. The reaction kinetics is very sensitive to the local environment around the active sites of the electrocatalyst, which is affected by the amount of adsorbed HQ and the PEDOT film thickness. Finally, the porous nature of PEDOT films, which have a high internal surface area, allows the HQ adsorption, deep inside the PEDOT film. In this sense, we suggest that the first step of hydroquinone oxidation is the formation of an acid–base complex between HQ and PEDOT.