On the Deposition and Dissolution of Zinc in Alkaline Solutions

The zinc/KOH‐zincate electrode reaction was investigated under high purity conditions with galvanostatic and potentiostatic transient techniques in the 0.1–3.0M and 0.0001–0.5M zincate concentration range. The exchange current density was found to be between 8 and 370 mA/cm2, with 40 mV/decade anodic and 120 mV/decade cathodic nominal Tafel slopes; an overpotential range of ± 100 mV was covered. The cathodic reaction orders were 1 for zincate, and −1 for hydroxyl ions. A four‐step mechanism, consistent with the kinetic data, is suggested. It consists of four consecutive dissociation reactions of the zincate complex, with two of them incorporating a single electron charge transfer. The rate‐determining step is The mechanism of the anodic and cathodic reactions is the same. The transients indicate only double layer charging and charge transfer processes. No surface diffusion effects or intermediate build‐up was observed (no pseudocapacitance). A rationalization is given for the mechanism. The effect of zinc surface preparation is discussed.