Scanning Electrochemical Microscopy of Electroactive Defect Sites in the Native Oxide Film on Aluminum

Abstract
Scanning electrochemical microscopy (SECM) of localized electron-transfer activity at Al surfaces covered by a 2-3 nm thick native oxide film is reported. electrodes prepared from Al rods (99.9965%) and foils (99.45% and 99.9995%) were imaged in acetonitrile solutions using the nitrobenzene (NB)/nitrobenzene radical anion redox couple as redox mediator. The SECM images reveal microscopic defect sites with radii between 1 and 10 μm that display high electron-transfer activity for NB reduction. The results indicate that the native oxide film on Al contains structural or electronic defects associated with high electronic conductivity. © 2000 The Electrochemical Society. All rights reserved.