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

Scanning electrochemical microscopy (SECM) of localized electron-transfer a ctivity at Al surfaces covered by a 2-3 nm thick native oxide film is repor ted. 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 i mages reveal microscopic defect sites with radii between 1 and 10 mum that display high electron-transfer activity for NB reduction. The results indic ate that the native oxide film on Al contains structural or electronic defe cts associated with high electronic conductivity. (C) 2000 The Electrochemi cal Society. S1099-0062(00)07-071-1. All rights reserved.