STUDY OF THE INITIAL-STAGES OF SILVER ELECTROCRYSTALLIZATION FROM SILVER THIOSULFATE COMPLEXES .1. MODELING OF THE SILVER NUCLEI FORMATION DURING THE INDUCTION PERIOD

Chronoamperometry was used to investigate the initial non-stationary s tages during the electrocrystallisation of silver thiosulphate complex es on a polycrystalline silver rotating disc electrode. At the beginni ng of the experiment a large current peak was always observed, followe d by a current decrease after several seconds. A new electrochemical r eaction model was introduced, suggesting the formation of 2D silver cl usters as a reaction step which precedes the actual moment of 3D nucle ation. By doing so, the nucleation phenomena observed during the so ca lled induction period do not have to be considered as being a stochast ic process consuming no current, as is often done in the literature. T he short time transients are simulated using a numerical computational method, solving the basic mass transport equations with the boundary conditions as a function of the newly proposed model. Satisfying fitti ng results are obtained, thus allowing one to deduce values for the di fferent electrochemical parameters involved. (C) 1997 Elsevier Science S.A.