Scanning electrochemical microscopy of electroactive defect sites in the native oxide film on aluminum

Scanning electrochemical microscopy (SECM) of localized electron-transfer activity at Al surfaces covered by a 2-3 nm thick native oxide film is reported. Al/Al2O3 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 mum 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. (C) 2000 The Electrochemical Society. S1099-0062(00)07-071-1. All rights reserved.