Influence of temperature on the reduction kinetics of Zn2+ at a mercury electrode

The reduction of Zn2+ at a mercury electrode has been studied by the a.c. impedance technique in the 263–318 K temperature range. Kinetic data have been analyzed in terms of a mechanism consisting of two consecutive charge transfer steps. The apparent activation enthalpies and charge transfer coefficients of both steps are found to be temperature independent. Differential capacity curves and potentials of zero charge of the NaClO4 supporting electrolyte solutions were measured at each temperature of interest. Double layer effects on the Zn2+ reduction rate constants were analyzed within the framework of the unequal distances of closest approach theory, and the corrected rate constants were found to be independent of supporting electrolyte concentration when allowance for changes in the Zn2+ activity coefficient was made. The implications of the activation parameter values on the nature of the rate determining steps are also discussed.