Temperature Effects on the Electrodeposition of Zinc

Abstract

The temperature dependence of the cyclic voltammetric profiles for the reduction of zinc into a static mercury drop electrode and the electrocrystallization of zinc onto a glassy carbon (GC) electrode have been examined using cyclic voltammetry and chronoamperometry, respectively. The quasi-two-dimensional growth and the microstructure of the deposited zinc film have also been characterized by video camera and scanning electron microscopy (SEM). The kinetic parameters D, α, and k for the reaction were calculated at three temperatures. Their values increase with increasing temperature. According to the slope, we determined the activation energy of the reaction to be −39.662 kJ mol−1. On the other hand, the chronoamperometric results showed that the nucleation density increases when the temperature increases. Moreover, the nucleation rate constant, A, is always very large at different temperatures, about s−1. This indicates that the mechanism of zinc electrocrystallization onto a GC electrode follows a three-dimensional (3-D) instantaneous nucleation and growth model within the controlled temperature range. As for the quasi-2-D growth forms and the microstructure of the zinc deposit, the experimental results showed that the fractal morphology of zinc exhibits isotropic growth with more and thicker branches at 273 K. In contrast, the fractal morphology of zinc exhibits anisotropic growth with fewer and thinner branches at 323 K. Similarly, the results obtained for the microstructure of the zinc deposit showed that plate-like crystals grow unintegrally like irregular hexagonal crystallites at 273 K, but the grains develop integrally and adequately at 323 K. © 2002 The Electrochemical Society. All rights reserved.