Electrochemical cell design for the impedance studies of chlorine evolution at DSA® anodes

A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS)studies of chlorine evolution on Dimensionally Stable Anodes (DSA®) has been developed. Despitebeing considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolutionat DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSAanode current densities for chlorine evolution because they allow gas accumulation at the electrodesurface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at highsodium chloride concentration (5 mol dm−3 NaCl) and high current densities (up to 140 mA cm−2)were recorded. Additionally, polarization curves and voltammograms were obtained showing little orno noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolutionreaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms

Ion-Transfer Voltammetric Behavior of Propranolol at Nanoscale Liquid-Liquid Interface Arrays

In this work, the ion-transfer voltammetric detection of the protonated β-blocker propranolol was explored at arrays of nanoscale interfaces between two immiscible electrolyte solutions (ITIES). Silicon nitride nanoporous membranes with 400 pores in a hexagonal arrangement, with either 50 or 17 nm radius pores, were used to form regular arrays of nanoITIES. It was found that the aqueous-to-organic ion-transfer current continuously increased steadily rather than reaching a limiting current plateau after the ion-transfer wave; the slope of this limiting current region was concentration dependent and associated with the high ion flux at the nanointerfaces. Electrochemical data were examined in terms of an independent nanointerface approach and an equivalent microdisc approach, supported by finite element simulation. In comparison to the larger interface configuration (50 nm radius), the array of 17 nm radius nanoITIES exhibited a 6.5-times higher current density for propranolol detection due to the enhanced ion flux arising from the convergent diffusion to smaller electrochemical interfaces. Both nanoITIES arrays achieved the equivalent limits of detection, 0.8 μM, using cyclic voltammetry. Additionally, the effect of scan rate on the charging and faradaic currents at these nanoITIES arrays, as well as their stability over time, was investigated. The results demonstrate that arrays of nanoscale liquid–liquid interfaces can be applied to study electrochemical drug transfer, and provide the basis for the development of miniaturized and integrated detection platforms for drug analysis

Simple and clear evidence for positive feedback limitation by bipolar behavior during scanning electrochemical microscopy of unbiased conductors

On the basis of an experimentally validated simple theoretical model, it is demonstrated unambiguously that when an unbiased conductor is probed by a scanning electrochemical tip (scanning electrochemical microscopy, SECM), it performs as a bipolar electrode. Though already envisioned in most recent SECM theories, this phenomenon is generally overlooked in SECM experimental investigations. However, as is shown here, this may alter significantly positive feedback measurements when the probed conductor is not much larger than the ti