Platinum cathodes maintained at very negative potentials in dimethylformamide (DMF) containing tetramethylarnmonium salts (TMAX) lead specifically to the decomposition of TMA(+) cation and the protonation of electrogenerated bases with the residual water. Therefore the electrogeneration in situ of TMAOH can yield a charging reaction with platinum at such reducing potentials. Sudden changes of potential (not larger than +0.3 V vs. the saturated calomel electrode (SCE)) allowed anodic reactions to occur, affording the superficial formation of platinum oxide. Voltarnmetric and chronocoulometric measurements strongly suggest that the platinum surface is uniformly covered by a compact monolayer of oxide, which can be reduced further according a well-defined adsorption-like step. This mode of superficial oxidation conducted on several types of platinum surfaces (smooth and platinized) allowed area changes to be followed in the course of multistep electrolyses. (c) 2005 Elsevier B.V. All rights reserved.