The Lead Anode in Alkaline Solutions: II . The Mechanism of Film Formation

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Abstract
The mechanism of the initial stages of formation has been investigated at a Pb anode in solutions, with the use of cyclic voltammetry, transient and steady‐state potential step methods, and modulated surface reflectance spectroscopy (MSRS). It has been found that, following the deposition and dissolution of at less positive potentials, deposition initiates according to an instantaneous three‐dimensional nucleation and growth mechanism under diffusion control. This is supported by the good match of the experimentally obtained i‐t response with the theoretically predicted one, by the observed changes in surface reflectivity with time and the marked effects of electrode rotation on the observed currents. Some dissolution of also occurs in these early stages of oxidation, forming the species, consistent with the observed Tafel slope and the excess of the anodic to cathodic charge in cyclic voltammetry. At still higher potentials or longer times, very thick porous films can be formed, consistent with film initiation by a nucleation and growth mechanism.

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