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Volume 210, 2018
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Nanoscale electrochemical kinetics & dynamics: the challenges and opportunities of single-entity measurements

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Abstract

The development of nanoscale electrochemistry since the mid-1980s has been predominately coupled with steady-state voltammetric (iE) methods. This research has been driven by the desire to understand the mechanisms of very fast electrochemical reactions, by electroanalytical measurements in small volumes and unusual media, including in vivo measurements, and by research on correlating electrocatalytic activity, e.g., O2 reduction reaction, with nanoparticle size and structure. Exploration of the behavior of nanoelectrochemical structures (nanoelectrodes, nanoparticles, nanogap cells, etc.) of a characteristic dimension λ using steady-state iE methods generally relies on the well-known relationship, λ2Dt, which relates diffusional lengths to time, t, through the coefficient, D. Decreasing λ, by performing measurements at a nanometric length scales, results in a decrease in the effective timescale of the measurement, and provides a direct means to probe the kinetics of steps associated with very rapid electrochemical reactions. For instance, steady-state voltammetry using a nanogap twin-electrode cell of characteristic width, λ ∼ 10 nm, allows investigations of events occurring at timescales on the order of ∼100 ns. Among many other advantages, decreasing λ also increases spatial resolution in electrochemical imaging, e.g., in scanning electrochemical microscopy, and allows probing of the electric double layer. This Introductory Lecture traces the evolution and driving forces behind the “λ2Dt” steady-state approach to nanoscale electrochemistry, beginning in the late 1950s with the introduction of the rotating ring-disk electrode and twin-electrode thin-layer cells, and evolving to current-day investigations using nanoelectrodes, scanning nanocells for imaging, nanopores, and nanoparticles. The recent focus on so-called “single-entity” electrochemistry, in which individual and very short redox events are probed, is a significant departure from the steady-state approach, but provides new opportunities to probe reaction dynamics. The stochastic nature of very fast single-entity events challenges current electrochemical methods and modern electronics, as illustrated using recent experiments from the authors’ laboratory.

Graphical abstract: Nanoscale electrochemical kinetics & dynamics: the challenges and opportunities of single-entity measurements

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Publication details

The article was received on 14 Sep 2018, accepted on 19 Sep 2018 and first published on 19 Sep 2018


Article type: Paper
DOI: 10.1039/C8FD00134K
Citation: Faraday Discuss., 2018,210, 9-28
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    Nanoscale electrochemical kinetics & dynamics: the challenges and opportunities of single-entity measurements

    M. A. Edwards, D. A. Robinson, H. Ren, C. G. Cheyne, C. S. Tan and H. S. White, Faraday Discuss., 2018, 210, 9
    DOI: 10.1039/C8FD00134K

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