Abstract
The concept of the Dynamic Electrical Double Layer (DEDL) is the physicochemical basis for electrochemical processes that proceed without an external source of current (electroless processes). The most characteristic feature of such processes is that they proceed only in an oscillation regime, with the anodic processes of electrode charging and the cathodic processes of its discharging alternating periodically at maximum values of the stationary electrode potential (the phenomenon of overpotential).
The DEDL model enables full account to be taken of this specific feature (adsorption and a heterogeneous chemical reaction at the anodic stage of the process and subsequent deposition of the metal in the cathodic stage) and the process to be described from a unified standpoint. In the framework of the DEDL model, the autocatalytic process of metal coating deposition depending on process conditions is described by modified Nernst or Tafel equations, which enable direct computation of both the values of the oscillating stationary electrode potential and of the characteristics of metal deposition (thickness and weight of the coating) by the kinetic dependence of “electrode potential vs time”.
It is demonstrated that both the modified Tafel equation for exchange current density (oscillation regime of the stationary electrode potential in electroless processes) and its classical interpretation for systems with constant values of the stationary electrode potential are particular cases of the Volmer – Butler equation.