NONEQUILIBRIUM FLUCTUATION THEORY IN ELECTROCHEMICAL NUCLEATION .2. EXPERIMENTAL-DETERMINATION OF CRITICAL FLUCTUATION IN SILVER NUCLEATIONONTO PLATINUM-ELECTRODE

Following part I, in this paper, the experiments for silver nucleation onto platinum electrode in AgNO3+NaNO3 solution were carried out to c ompare the theoretical equations with experimental data. The theoretic al examination predicted that after double layer charging current a mi nimum current emerges, accompanied with rapid monolayer nucleus format ion. Since the monolayer nuclei prepare the substrates for the followi ng extensive nucleation, the stage when the nuclei are formed is of mu ch importance. From the experiments for double layer charging current, it was decided that the nucleus formation is activated at the final s tage of the charging. This result reinforces the theoretical predictio n that the monolayer nuclei are formed by the minimum current. Extrapo lation of the minimum current to the critical state gave the critical autocorrelation distance and the average critical concentration fluctu ation on the completely active surface. The autocorrelation distance w as determined as (a) over tilde(cr) = 7.82 x 10(-4) m at 300 K, which is quite large in comparison with the scale of the fluctuation and in good agreement with the value obtained in nickel pitting dissolution. On the other hand, as discussed in the previous paper, since there is no intense specific adsorption of ions onto the electrode surface, the electrostatic interaction between the ions accelerates the simultaneo us adsorption of Ag+ ion and NO3- ion. Therefore, it was concluded tha t the concentration of the supporting electrolyte NaNO3 also fluctuate s with the Ag+ ionic concentration. (C) 1997 American Institute of Phy sics.