Effect of Complex Formation on Mass Transfer during Metal Electrodeposition on Rotating Disk Electrode

The effect of complex formation on the mass transfer during the metal electrodeposition on a rotating disk electrode from the solution containing three types of ions (metal cation, cationic complex, and non-electroactive anion) is studied theoretically. The dimensionless Nernst–Planck equations in the approximation of solution electroneutrality, which take into account the electro-diffusion and convective transfer of all types of ions and the homogeneous reaction of complex formation, are used as the mathematical model. The kinetics of electrochemical reactions is taken into account using the Butler–Volmer equations. In contrast to the known works, the approximations of the Nernst layer, equal diffusion coefficients of all types of ions, and equilibrium complex formation reaction are not used. As a result of numerical solution, the distributions of concentration, potential, and the rate of complex formation reaction are obtained at various parameters of the system under consideration. It is shown that the equilibrium and rate constants of complex formation reaction and the ratio between the diffusion coefficients of complex cation and anion have the strongest effect on the mass transfer.