Electrochemical and quartz crystal microbalance evidence for mediation and direct electrochemical reactions of small molecules at tetrathiafulvalene-te

Rotating disk electrode experiments were used to investigate the electrochemical kinetics of ferricyanide, ascorbic acid and catechol in 0.5 M sodium phosphate buffer (pH 7) at TTF-TCNQ electrodes. Apparent transfer coefficients (α) of approximately 0.3 were obtained for the oxidation of ascorbic acid and catechol, and suggest that the oxidation may involve heterogeneous catalysis at the TTF-TCNQ electrode surface. For ferricyanide α = 0.5, indicating direct electron transfer. The behavior of the surface was subsequently characterized using in situ quartz crystal microbalance (QCM) measurements. QCM results suggest that a TCNQ⁰ rich surface is being produced throughout most of the potential window used during rotating disk electrode experiments. A mechanism is proposed which can account for the low apparent transfer coefficient and which involves TCNQ⁰.