Separation of transient partial fluxes of nucleation/growth of a new phase and electrode reaction by the chronoamperometry method

Abstract

One of the basic methods of studying of the electrochemical formation of a new phase is by the obtaining of potentiostatic i,t-dependences with their processing within the framework of various models of nucleation. The situation is highly complicated in the case of some Faraday processes that proceed alongside the phase formation. On the basis of the mass balance analysis in conditions of 3-dimensional (3D) nucleation using the data on electrode reaction kinetics, the procedure of graphical processing of the complete i,t-curves, which allows to reveal a partial nucleation flux is suggested. The procedure was used when studying the following electrochemical processes: (i) cathodic evolution of hydrogen on transition metals from acidic sulphate solutions, and (ii) selective anodic dissolution (dealloying) of binary Au-containing alloys at overcritical potentials where nonequilibrium phase transition of gold occurs. It was established that both processes are carried out in a mode of instantaneous activation of nucleation sites and controlled by the lateral diffusion of adsorbed atoms of hydrogen or gold, respectively, to its hemispherical nuclei. The role of the solid electrode composition, overpotential and presence of surface-active organic substances in a solution is investigated.