Anodic Films on Zinc and the Formation of Cobwebs

Powers, R. W.

doi:10.1149/1.2411652

Cited by 37 publications

(36 citation statements)

References 8 publications

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“…When investigating the oxidation behavior of a Zn electrode in concentrated alkaline KOH electrolyte, Powers et al [27][28][29] found that two types of ZnO could be formed on the surface of the polished Zn electrode. In the case of no convection current, type I ZnO crystals were first homogeneously nucleated in the electrolyte.…”

Section: Growth Mechanism Of Bunched Zno Nw Arrays In Alkali Solutionmentioning

confidence: 99%

Hierarchical Shelled ZnO Structures Made of Bunched Nanowire Arrays

Jiang

Zhou

Fang

et al. 2007

Adv Funct Materials

214

111

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The size‐ and morphology‐controlled growth of ZnO nanowire (NW) arrays is potentially of interest for the design of advanced catalysts and nanodevices. By adjusting the reaction temperature, shelled structures of ZnO made of bunched ZnO NW arrays are prepared, grown out of metallic Zn microspheres through a wet‐chemical route in a closed Teflon reactor. In this process, ZnO NWs are nucleated and subsequently grown into NWs on the surfaces of the microspheres as well as in strong alkali solution under the condition of the pre‐existence of zincate (ZnO22–) ions. At a higher temperature (200 °C), three different types of bunched ZnO NW or sub‐micrometer rodlike (SMR) aggregates are observed. At room temperature, however, the bunched ZnO NW arrays are found only to occur on the Zn microsphere surface, while double‐pyramid‐shaped or rhombus‐shaped ZnO particles are formed in solution. The ZnO NWs exhibit an ultrathin structure with a length of ca. 500 nm and a diameter of ca. 10 nm. The phenomenon may be well understood by the temperature‐dependent growth process involved in different nucleation sources. A growth mechanism has been proposed in which the degree of ZnO22–saturation in the reaction solution plays a key role in controlling the nucleation and growth of the ZnO NWs or SMRs as well as in oxidizing the metallic Zn microspheres. Based on this consideration, ultrathin ZnO NW cluster arrays on the Zn microspheres are successfully obtained. Raman spectroscopy and photoluminescence measurements of the ultrathin ZnO NW cluster arrays have also been performed.

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Section: Growth Mechanism Of Bunched Zno Nw Arrays In Alkali Solutionmentioning

confidence: 99%

Hierarchical Shelled ZnO Structures Made of Bunched Nanowire Arrays

Jiang

Zhou

Fang

et al. 2007

Adv Funct Materials

214

111

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“…2, Powers observed that the formation of ZnO occurred in two stages if convection currents were absent in the electrolyte, whereas it proceeded in one step in the presence of convection currents in the electrolyte. [3][4][5] In the absence of convection currents, individual ZnO crystals were first nucleated homogeneously in the electrolyte, and the size and number of these crystals increased upon further discharge. Powers designated these crystals as type I ZnO.…”

mentioning

confidence: 99%

Morphology and Spatial Distribution of ZnO Formed in Discharged Alkaline Zn/MnO[sub 2] AA Cells

Horn

Shao‐Horn

2003

J. Electrochem. Soc.

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A novel experimental technique was developed to extract the KOH solution from the porous zinc electrode in an inert environment. This technique permits the ZnO/electrolyte interface, the ZnO/Zn particle interface, and the spatial distribution of ZnO in the porous anode in commercial alkaline Zn/MnO 2 AA batteries to be characterized for the first time by optical and scanning electron microscopy. Both type I and type II ZnO, previously observed in oxidation of planar zinc electrodes, were found in each completely discharged zinc particle in the porous electrode. The morphology, size, and location of these two ZnO forms strongly suggested that they were produced by a solution-precipitation route. The drain rate had a significant impact on the spatial distribution of ZnO in the anode. The segregation of ZnO near the separator became dominant at drain rates higher than 500 mA. The mechanisms by which the morphology and segregation of ZnO within the porous electrode could result in the reduced battery runtime are discussed.Growth and advances in the portable electronic industry require commercial alkaline Zn/MnO 2 AA batteries to function under high power and high drain conditions. Unfortunately, AA batteries operate inefficiently at high drain rates. 1 For example, the runtime of a AA battery at a 1000 mA continuous drain rate is typically less than 20% of that discharged at 10 mA. This inefficiency is a result of severe polarization across the Zn ͑anode͒ and MnO 2 ͑cathode͒ electrodes at high drain rates. The Zn/MnO 2 AA cell has a bobbin-type construction, where both electrodes are porous, as shown in Fig. 1. The anode consists of zinc powder that is usually suspended in a gelled electrolyte of concentrated KOH in water, and the cathode includes a physical mixture of electrolytic manganese dioxide and graphite, respectively. 1 It is accepted that the oxidation of zinc proceeds by a dissolution-precipitation process, while MnO 2 is reduced by a solid-state intercalation of H ϩ into the MnO 2 lattice, as followsRecent efforts in analyzing the AA battery discharge performance by mathematical modeling have suggested that the spatial distribution of the discharge product, ZnO, within the anode can have a significant effect on the electrode polarization and the battery performance under high drain rates. 2 In addition, the morphology and spatial distribution of ZnO may have a significant impact on the rechargeability of secondary alkaline systems that utilize a metallic zinc anode. Although the morphology and reaction mechanism of ZnO formation on planar zinc electrodes in concentrated KOH electrolytes is well studied, 3-12 limited information is available on porous zinc electrodes. Our study aims to understand the nucleation and growth process of ZnO and to investigate the effect of drain rates on the spatial distribution of ZnO in discharged porous zinc anodes.The morphology and formation mechanism of ZnO on the surface of polished zinc-plate electrodes in concentrated KOH electrolytes was first studied by Powers et al...

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“…On the contrary, from the result of surface morphology observation and the numerical model, we suggest the important role of this thin layer densely packed with small ZnO or Zn(OH) 2 precipitates, through which zincate ion diffuses out and in which ZnO or Zn(OH) 2 precipitates aggregate to grow on the first layer adjacent to Zn anode surface. The critical solubility concentration of Zn(OH) 4 2-ion was estimated to be 0.6-0.7M (around t= 600 seconds) after formation of first porous layer.…”

Section: Sem Observationmentioning

confidence: 71%

“…[2], Eq. [6] suggests that the accumulating Zn(OH) 4 2− ion increases the refractive index difference, whereas the depleting OH − ion accompanying Eq.…”

Section: H 2 O = O 2 (G)+ 4hmentioning

confidence: 99%

“…[6] suggests that the accumulating Zn(OH) 4 2− ion increases the refractive index difference, whereas the depleting OH − ion accompanying Eq. [2] has an opposite effect on the refractive index difference due to the Zn(OH) 4 2− ion. The effect of optical beam deflection in a steep refractive index gradient was taken into account, although the optical correction was very small.…”

Section: H 2 O = O 2 (G)+ 4hmentioning

confidence: 99%

See 1 more Smart Citation

(Invited) Zinc Surface Morphological Variations and Ionic Mass Transfer Rates in Alkaline Solution

Arise

Homma²,

McLarnon

et al. 2011

ECS Trans.

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A horizontal upward-facing Zn anode was electrochemically dissolved in aqueous alkaline electrolyte. A plane-parallel upwardfacing Ni(OH) 2 /NiOOH cathode was combined with this Zn anode in a single cell, divided by a polymer separator. This configuration can be considered as a model single pore inside the mesoporous space of a Zn-NiOOH battery cell. It also insures that ionic mass transfer by diffusion and migration is dominant over that by natural convection. The morphological variations of the Zn anode surface plane were examined during the discharge operation of the ZnNiOOH model cell. The two-dimensional transient concentration profiles of each ion accompanying the electrochemical dissolution of Zn anode in the alkaline electrolyte were numerically calculated. The surface morphological variations of the Zn anode were discussed with the aid of numerical simulation. ZnO precipitation on the Zn anode surface was confirmed to be dependent on the horizontal distance from the cell separator. The numerical model provides insight to the analysis of observed morphological variations along the anode surface.

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Anodic Films on Zinc and the Formation of Cobwebs

Cited by 37 publications

References 8 publications

Hierarchical Shelled ZnO Structures Made of Bunched Nanowire Arrays

Hierarchical Shelled ZnO Structures Made of Bunched Nanowire Arrays

Morphology and Spatial Distribution of ZnO Formed in Discharged Alkaline Zn/MnO[sub 2] AA Cells

(Invited) Zinc Surface Morphological Variations and Ionic Mass Transfer Rates in Alkaline Solution

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