NONEQUILIBRIUM FLUCTUATION THEORY IN ELECTROCHEMICAL NUCLEATION .3. EXPERIMENTAL-DETERMINATION OF FLUCTUATION GROWTH-RATE IN SILVER NUCLEATION ONTO PLATINUM-ELECTRODE

Following part II, in this paper, some analytical equations concerning nucleation current were experimentally examined for silver nucleation onto platinum electrode in AgNO3 + NaNO3 solution. After passing the minimum state, the nonequilibrium fluctuations being to unstably grow, being accompanied with active nucleation. Resultant current can be th eoretically expressed as an exponential function of the second order o f time, and its time coefficient depends on the concentrations of both depositing metal ion and supporting electrolyte and also the overpote ntial. These theoretical predictions were experimentally ascertained. Accordingly, it was concluded that the nucleation current is described by the quantities with regard to the fluctuations and the double laye r. Furthermore, the maximum peak current appearing after nucleation gr owth current was investigated. As discussed before, the semilog plot o f the current against the overpotential gave almost the same slope of the Tafel equation for silver deposition. Observed values of the curre nt were almost equal to those measured by applying current steps to si lver electrode. Finally, the diffusion current was expected after pass ing the peak current. Then, it was clarified that limiting diffusion c urrent, indifferent to the initial value of the overpotential, flows a ccording to the Cottrel equation. (C) 1997 American Institute of Physi cs.