Kinetic differentiation of bulk/interfacial oxygen reduction mechanisms at/near liquid/liquid interfaces using scanning electrochemical microscopy

Abstract

a b s t r a c tThe present work describes the application of scanning electrochemical microscopy (SECM) in the feedback mode to determine the kinetics of oxygen reduction at or near the liquid/liquid interface -between water and 1,2-dichloroethane (w/DCE). The system contained decamethylferrocene (DMFc) in DCE as the electron donor and acids in water as a proton source. In this approach, decamethylferrocenium (DMFc + ) is reduced at the tip of a microelectrode in DCE and the electrogenerated DMFc reacts with protons and oxygen to be re-oxidized in a following chemical reaction (catalytic EC' mechanism). When a high Galvani potential difference was applied across the liquid/liquid interface, protons would transfer rapidly to the organic phase. Under this condition, SECM approach curves toward the liquid/liquid interface showed dramatic current increases at distances far from the interface. This indicates that oxygen reduction takes place mainly in the bulk DCE; however, at lower Galvani potential differences, where the proton transfer is slow, oxygen reduction was also observed at the interface. Finally, SECM feedback mode measurements with the tip approaching a conductive substrate were used to determine the kinetics of the homogeneous reaction, with an obtained apparent rate constant of 0.2-0.5 m 3 mol À1 s À1 .

Probing TCNQ‐mediated Metal Reduction Reactions at Liquid‐liquid Interface with SECM

“…Additionally, the repeatability of the experiments with SECM against a liquid/liquid interface can be inadequate, as has been discussed earlier e.g. by Deng et al [40] Cu nanoparticles have catalytic properties, which are likely to affect the reaction kinetics. Additionally, it should be mentioned especially in the case of Figure 8 that simulations of negative feedbacks are more sensitive to the RG values.…”

Oxygen Absorption in Electrocatalyst Layers Detected by Scanning Electrochemical Microscopy

“…Micrometer scale spatial and millisecond scale temporal resolution is obtained with typical microelectrodes. SECM has been utilized in various applications from biology[ 1 , 2 ] to energy devices. [3] …”

Ion Selective Detection Based on the Nuances of the Kinetic Fingerprint for Ion Transfer at Soft Interfaces

“…Besides the ISEs, electrochemistry at the oil/water (o/w) interface or the interface between two immiscible electrolyte solutions (ITIESs) provides another unique electrochemical platform for sensing a broad spectrum of redox-inactive ionic analytes. − Up to now, charge (electron or ion) transfer at the externally polarizable ITIES as a function of Galvani/inner potential difference can be studied by the classical four-electrode configuration, − the droplet and thin-film modified three-electrode system, − the micro/nanopipettes − and/or holes, and their arrays, and scanning electrochemical microscopy (SECM). − Very recently, we have enriched the methodology library of the ITIES electrochemistry: ion transfer (IT) at ITIES can be investigated at a single emulsion oil droplet that is dispersed in aqueous. Based on this method and our prior efforts in introducing Fourier transformed sinusoidal voltammetry (FT-SV) into single particle electrochemistry via collisions, we obtained a quantitative full voltammogram of IT with chemical resolution for an emulsion droplet .…”