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Nanoscale Visualization of Electrochemical Activity at Indium Tin Oxide Electrodes
journal contribution
posted on 2022-03-22, 00:00 authored by O J Wahab, Minkyung KangMinkyung Kang, G N Meloni, E Daviddi, P R UnwinIndium tin oxide (ITO) is a popular electrode choice, with diverse applications in (photo)electrocatalysis, organic photovoltaics, spectroelectrochemistry and sensing, and as a support for cell biology studies. Although ITO surfaces exhibit heterogeneous local electrical conductivity, little is known as to how this translates to electrochemistry at the same scale. This work investigates nanoscale electrochemistry at ITO electrodes using high-resolution scanning electrochemical cell microscopy (SECCM). The nominally fast outer-sphere one-electron oxidation of 1,1′-ferrocenedimethanol (FcDM) is used as an electron transfer (ET) kinetic marker to reveal the charge transfer properties of the ITO/electrolyte interface. SECCM measures spatially resolved linear sweep voltammetry at an array of points across the ITO surface, with the topography measured synchronously. Presentation of SECCM data as current maps as a function of potential reveals that, while the entire surface of ITO is electroactive, the ET activity is highly spatially heterogeneous. Kinetic parameters (standard rate constant, k, and transfer coefficient, α) for FcDM0/+ are assigned from 7200 measurements at sites across the ITO surface using finite element method modeling. Differences of 3 orders of magnitude in k are revealed, and the average k is about 20 times larger than that measured at the macroscale. This is attributed to macroscale ET being largely limited by lateral conductivity of the ITO electrode under electrochemical operation, rather than ET kinetics at the ITO/electrolyte interface, as measured by SECCM. This study further demonstrates the considerable power of SECCM for direct nanoscale characterization of electrochemical processes at complex electrode surfaces.
History
Journal
Analytical ChemistryVolume
94Issue
11Pagination
4729 - 4736Publisher
American Chemical SocietyLocation
Washington, D.C.Publisher DOI
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ISSN
0003-2700eISSN
1520-6882Language
engPublication classification
C1 Refereed article in a scholarly journalUsage metrics
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