Mechanism of Electrodeposition of Lead Dioxide from Nitrate Solutions

The lead dioxide electrodeposition (LDE) from nitrate electrolytes is studied by the rotating disk electrode, cyclic voltammetry, and electrode impedance methods. A four-stage kinetic scheme of the LDE reaction is proposed: (1) the electron transfer and generation of oxygen-containing species on the electrode surface; (2) the species interact with lead ions, forming an oxygen-containing intermediate product of Pb(III) of the type Pb(OH)²⁺, which is not fixed on the electrode surface; (3) the product is oxidized, with the transfer of the second electron, forming compounds of Pb(IV) associated with oxygen (of the type Pb(OH)²⁺₂); and (4) the latter decomposes via a chemical mechanism to form PbO₂. The rate-determining stage of the LDE process is essentially dependent on the potential and state of the electrode surface, concentration of Pb(II) ions in solution, and hydrodynamic conditions of experiment. The proposed scheme explains within a unified mechanism of the LDE reaction all the experimental data obtained both in this work and in the literature.