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

Haiqiang Deng, Pekka Peljo, Dmitry Momotenko, Fernando Cortes-Salazar, T. Jane Stockmann, Kyösti Kontturi, Marcin Opallo, Hubert H. Girault*

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    15 Citations (Scopus)

    Abstract

    The 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(-1) s(-1). (C) 2014 Elsevier B.V. All rights reserved.

    Original languageEnglish
    Pages (from-to)101-109
    Number of pages9
    JournalJournal of Electroanalytical Chemistry
    Volume732
    DOIs
    Publication statusPublished - 15 Oct 2014
    MoE publication typeA1 Journal article-refereed

    Keywords

    • ITIES
    • Oxygen reduction
    • Decamethylferrocene
    • SECM
    • Catalytic EC'
    • LIQUID-LIQUID INTERFACE
    • IMMISCIBLE ELECTROLYTE-SOLUTIONS
    • METAL-FREE PORPHYRIN
    • ION TRANSFER
    • GRAPHITE-ELECTRODES
    • WATER-NITROBENZENE
    • CHEMICAL-REACTIONS
    • MOLECULAR-OXYGEN
    • COLLECTION MODE
    • CHARGE-TRANSFER

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