Nonequilibrium fluctuation theory in electrochemical nucleation. III. Experimental determination of fluctuation growth rate in silver nucleation onto platinum electrode

Abstract

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 theoretically expressed as an exponential function of the second order of time, and its time coefficient depends on the concentrations of both depositing metal ion and supporting electrolyte and also the overpotential. 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 layer. Furthermore, the maximum peak current appearing after nucleation growth current was investigated. As discussed before, the semilog plot of the current against the overpotential gave almost the same slope of the Tafel equation for silver deposition. Observed values of the current were almost equal to those measured by applying current steps to silver electrode. Finally, the diffusion current was expected after passing the peak current. Then, it was clarified that limiting diffusion current, indifferent to the initial value of the overpotential, flows according to the Cottrel equation.