Observations of an Operating Zinc‐Pore Electrode

Abstract

A single-pore cell with a 14 ~m spacing is used as an analog of a porous zinc anode and cathode for examinations of surface morphology and reaction profile in 10M KOH, saturated ZnO. At the anode the dissolution-precipitation mode of ZnO formation is corroborated and the effective depth of reaction penetration is initially 0.09 cm. Structure of the deposited ZnO film is determined by SEM to be porous with 80% porosity and 1500A pores. At the cathode, H~ bubbles are found to be associated with the initiation and growth of zinc dendrites.

The Dissolution and Passivation of Zinc in Concentrated Aqueous Hydroxide

“…With the reduced dissolution current, the zincate concentration declines and the pH increases, redissolving the Zn(OH)2 (type I) and ZnO (type II) films. This mechanism is consistent with the observation (59) that Zn can be reactivated in a thin layer cell by the addition of very small amounts of fresh hydroxide. In the absence of the type I film, reactivation results initially in a current limited only by the hydroxide migration resistance.…”

Experimental and Theoretical Study of Concentration Distributions in a Model Pore Electrode: II . Mathematical Models and Comparison to Experiment

“…zaki and Yao (9) for an array of cylindrical pores and with the results of Katan et al (36) and Flattet al (33) for a single-model pore. Experimental studies of actual porous zinc electrodes, however, sometimes suggest that the reaction distribution is more uniform (14).…”

“…This suggests that the potassium zincate concentration near the pore mouth reaches supersaturation and could lead to type I precipitation within the electrolyte 14 (37,38). Also, the decrease of potassium hydroxide concentration might lead to passivation of the zinc electrode and the formation of a tightly adherent type II film (36).…”

Experimental and Theoretical Study of Concentration Distributions in a Model Pore Electrode: I . Measurement of Two‐Dimensional Concentration Gradients in a Zinc Model Pore

“…5 are negative, indicating that the beam was deflected toward the electrode. [3], the solution refractive index gradient grows or decays in response to changes in these concentration gradients. The significance of this and other observations will be discussed quantitatively by comparison to a two-dimensional model in the companion theoretical paper.…”

“…[3]. The variation of refractive index with concentration, On/Oci (q), was measured for each of these) The individual concentration gradients cannot, however, be determined so easily.…”