The corona of a surface bubble promotes electrochemical reactions

Abstract

The evolution of gaseous products is a feature common to several electrochemical processes, often resulting in bubbles adhering to the electrode’s surface. Adherent bubbles reduce the electrode active area, and are therefore generally treated as electrochemically inert entities. Here, we show that this general assumption does not hold for gas bubbles masking anodes operating in water. By means of imaging electrochemiluminescent systems, and by studying the anisotropy of polymer growth around bubbles, we demonstrate that gas cavities adhering to an electrode surface initiate the oxidation of water-soluble species more effectively than electrode areas free of bubbles. The corona of a bubble accumulates hydroxide anions, unbalanced by cations, a phenomenon which causes the oxidation of hydroxide ions to hydroxyl radicals to occur at potentials at least 0.7 V below redox tabled values. The downhill shift of the hydroxide oxidation at the corona of the bubble is likely to be a general mechanism involved in the initiation of heterogeneous electrochemical reactions in water, and could be harnessed in chemical synthesis.

Electrochemiluminescence with semiconductor (nano)materials

“…This explanation implies the photogeneration of highly energetic holes, since the standard potential of the OHc/OH À couple is 1.90 V vs. SHE. 177,178 Due to the conducting nature of the working electrodes, such a mechanism is very different from the PECL occurring on classical SC photoelectrodes. This is further stressed by the fact that no shi of onset potential was measured upon illumination.…”

Deciphering the Mechanisms of Electrochemiluminescence by Spatially Resolved Measurements

“…Since then, numerous investigations on luminophores, coreactants, reaction mechanisms and applications of ECL have been carried out [6–9] . Benefiting from its low background, high sensitivity and facile spatiotemporal control, ECL has been widely used in the fields of bioanalysis, [10–14] catalysis, [15,16] bioimaging, [17,18] bipolar electrochemistry, [19–21] etc. In particular, the classical coreactant ECL system involving tris(2,2’‐bipyridine) ruthenium(II) (Ru(bpy) 3 2+ ) and tri‐ n ‐propylamine (TPrA) has been successfully used in commercial in‐vitro diagnostics, which can diagnose more than 150 diseases, including anemia, cardiopathy, hepatitis, etc [22] .…”

Plasmonic Imaging of Tuning Electron Tunneling Mediated by a Molecular Monolayer

“…Furthermore, this approach opens up a promising way to evaluate the performance of organic-monolayer functionalized system and brings various practical applications in photocatalysis, electrocatalysis, and energy transfer in ionic batteries. Inspired by the work of a surface bubble promoting electrochemical reactions, 28 this technique can also be applied to study the redox activity of different micronanointerfaces.…”