Ionic mass transfer accompanying anodic dissolution of zinc in alkaline solution

Holographic interferometry was applied in situ to measure the ionic mass-transfer rates near upward-facing zinc anodes dissolving at high current densities in aqueous KOH solutions. The time-varying interference fringe patterns were converted to individual concentration profiles of Zn(OH)(4)(2-), K+, and OH- ions. The measured ionic concentration profiles agreed well with those predicted by a transient diffusion model for a multicomponent electrolyte. When a zinc anode was electrochemically dissolved in 3 wt % KOH electrolyte, the anode potential abruptly shifted in the noble direction, immediately followed by gas evolution. The onset time for this potential rise and accompanying gas evolution agreed well with the calculated time interval required to drive the OH- ion concentration to zero at the zinc electrode surface. The present model can be applied to not only optimize zinc cell designs but also develop a control method for trouble-free, safe operation of a zinc battery without gas evolution. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.2131819] All rights reserved.