An electrochemical study of the bismuth oxide Bi2O3 with a cavity microelectrode coupled in situ to Raman microspectroscopy allowed species transformations during the redox behavior of this oxide to be identified. It was shown that the electroactive species are probably bismuth oxy-hydroxides rather than Bi2O3 when a potential is applied, whereas they are Bi2O3 on open circuit voltage. (C) 2001 Elsevier Science Ltd. All rights reserved.