Theoretical and experimental study of the ECE mechanism at microring electrodes

Microring electrodes are useful for the investigation of reaction kinetics due to their large perimeter to area ratio and compact nature but have hitherto been limited in application due to the absence of the underpinning theory. In this paper, we apply the conformal mapping technique recently developed by Amatore et al. [C. Amatore, A.I. Oleinick, I.B. Svir, J. Electroanal. Chem. 564 (2004) 245] for the simulation of chronoamperometry at very thin microring electrodes, where an ECE-type mechanism is in operation. The simulated results are compared with data obtained from chronoamperometry experiments with bromonitrobenzenes at lithographically fabricated gold microring electrodes. Best fit parameters for the experimental system are determined using an automatic fitting procedure. The dark electrochemical reduction of ortho-bromonitrobenzene (o-BNB) in 0.1 M tetrabutylammonium/acetonitrile solution is consistent with an ECE-type mechanism and a value of 20 s−1 is theoretically determined for the unimolecular cleavage of the o-BNB radical anion, in good agreement with that previously reported for similar chemical systems.