Some potentiostatic studies on zinc

Sanghi, Indra; Fleischmann, M.

doi:10.1016/0013-4686(59)85004-0

Cited by 37 publications

(24 citation statements)

References 17 publications

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“…The competition between the oxide/hydroxide film fo17nation and HER rates can result in a partially covered cadmium surface. It is significant to note that a similar but more pronounced cathodic transition region has been observed for zinc in slightly alkaline solutions [10]. Results obtained by using the rotating ring disc technique [11] demonstrated that a Cd(OH)2 film is already present on cadmium as the HER is taking place.…”

Section: Introductionmentioning

confidence: 57%

Depolarization of the hydrogen evolution reaction on cadmium electrodes in alkaline media

1988

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Depolarization of the hydrogen evolution reaction on high purity polycrystalline cadmium electrodes in alkaline media (12 ~< pH ~ 14 and 5 ~ T ~< 55 ~ C) produced by cathodization in the range of potential comprised between the Cd/Cd(OH)2 electrode potential and the net HER potential wader solution stirring conditions has been studied. The depolarization effect depends on the perturbing potential programme and it is little affected by the alkaline cation in solution. Results are discussed in terms of three concurrent reactions, namely the electrochemical formation of Cd(OH)2 and soluble Cd(OH)3, the HER and the electrocrystallization of cadmium renewing the fresh active sites for the HER, SEM micrographs of activated cadmium electrodes reveal a heterogeneous surface topography of the new cadmium layers.

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Section: Introductionmentioning

confidence: 57%

Depolarization of the hydrogen evolution reaction on cadmium electrodes in alkaline media

1988

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“…The current increases in a nearly linear fashion with potential (25,36) between "b" and "c" reaching a maximum at "d" and attaining a plateau value "e" before passivation. Two peaks in the region "cf" have been observed at very low potential sweep rates (< 1 mV sec -1) by other workers (21,26,42). The peaks were interpreted by Powers and Breiter (21) Active dissolution.hWe observed that the form of the repetitive sweep voltammogram depends critically on both electrode rotation speed and electrolyte temperature.…”

Section: Fig 2 Rr De Cell Constructionmentioning

confidence: 82%

The Dissolution and Passivation of Zinc in Concentrated Aqueous Hydroxide

McKubre

Macdonald

1981

J. Electrochem. Soc.

121

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The rotating ring-disk electrode has been applied in this study to the related phenomena of dissolution, current oscillation, and passivation of zinc in concentrated aqueous NaOH. The results of potentiostatic and potentiodynamic experiments are compared with those of previous workers, and a physical model is proposed to describe the anodic behavior of zinc in four successive potential regions: active dissolution, prepassivation, pseudopassivation, and true passivation.The requirements for high specific energy, high specific power, and low cost make zinc an attractive negative electrode material for aqueous alkaline batteries in electric vehicular applications (1). However, a number of specific limitations await satisfactory resolution. Recent studies have been concerned with the limitations of cycle life associated with dendritic (2-5) and nonadherent (6-9) zinc deposition during charging, and with the problems of electrode shape change with cycling (1, 2, 10). The shelf life and cycle life of zinc battery electrodes is also limited by the corrosion of zinc in concentrated alkali (11)(12)(13).In the present study we focus on the related processes of anodic dissolution and passivation. Rapid discharge of the zinc electrode is associated largely with the high solubility of Zn(II) as a zincate ion (14, 15) in alkaline solutions. At high currents, however, zinc discharge is often inhibited by the formation of a passivating zinc oxide or hydroxide layer by a dissolution-precipitation mechanism (16-28). Before the onset of passivation, the discharge of zinc is generally agreed (21) to proceed via the formation of complex hydroxyl zincate anion. The nature of this anion has been the subject of considerable thermodynamic (14, 29-31) and spectroscopic (15, 32-34) investiga.tion, and is thought to have the form Zn (OI-I)4 ~+ in strongly alkaline solutions. However, the spectroscopic investigations of Jackovitz and Langer (32) suggest that "only a small fraction, about one-sixth of the anodically dissolved zinc, was converted to Zn (OH)42-" Experimental ProcedureExperiments were performed using a rotating ringdisk electrode (RRDE). The importance of adequate hydrodynamic control in studies of zinc dissolution and passivation phenomena has been stressed by several authors (20,26,35,36).The RRDE was constructed using a vitreous carbon~ ring with a 99.999% purity zinc disk, as shown in Fig. 1. Vitreous carbon constitutes a nearly ideal, nonporous, inert ring material for current collection at large cathodic potentials. The radius ratios rs/r~ and re~r1 exceed those tabulated by Albery et al. (37) andPleskov (38), and the electrode collection efficiency was determined experimentally in O.IM K3Fe(CN)e with 1.0M NaOH supporting electrolyte. This calibration procedure has been described previously (39). At 20~ the measured collection efficiency was 70.9 • 0.2%. Details of the rotating ring-disk electrode construction are shown in Fig. 1. " Electrochemical Society Active Member. Present address: The Experiments were conducted in a...

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“…The only apparent way to understand such a phenomenon is to assume the existence of a catalyst on the zinc electrode that was not present at --1.36V. Sanghi and Fleischmann in 1959 were the first to present some evidence for the existence of this kind of catalysis (6). On applying an increasingly positive poten.~ial to a zinc electrode in a very dilute (0.01-0.1M) KOH solution, the current was anodic from the rest value until passivation ensued.…”

Section: Hydrogen Evolutionmentioning

confidence: 99%

Film Formation and Hydrogen Evolution on the Alkaline Zinc Electrode

Powers

1971

J. Electrochem. Soc.

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The duplex structure of anodic films formed in concentrated KOH solutions with convection nearly absent--a hydrodynamic condition present near a hattery plate in proximity to a separator--has been confirmed on high-purity polycrystalline zinc and to a more limited extent on some polycrystalline zinc alloys as well Previously, the use of a very slow potential scan with simultaneous microscopic observation of single-crystal zinc electrodes showed that a precipitated coating of ZnO particles (type I film) overlies a more coherent film also of ZnO (type II). The experimental conditions required for following stages in the formation of the precipitated film, the one most difficult to observe, are defined more explicitly in this paper. Evidence is presented that the type II film serves as a catalyst for hydrogen evolution at potentials anodic to the zinc/zinc oxide equilibrium value. Hydrogen bubbles, whose formation is so catalyzed, can mechanically dislodge overlying passivating film to cause reactivation of the electrode. The presence of complex tin or lead anions at concentrations about 10-3M (molar) in KOH solutions gives rise to very smooth, almost imperceptible, films of metallic tin or lead over the zinc electrode surface. Such films are made visible, though, during zinc dissolution as they rumple and eventually gather into a wad after being undercut. These foreign metal films inhibit the dissolution of zinc to an extent that depends on the particular complex anion, its concentration, and exposure time to the zinc surface. Lead films can be made sufficiently inhibitive that zinc dissolution is reduced 'to such a rate that very little precipitation of ZnO occurs.

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Some potentiostatic studies on zinc

Cited by 37 publications

References 17 publications

Depolarization of the hydrogen evolution reaction on cadmium electrodes in alkaline media

Depolarization of the hydrogen evolution reaction on cadmium electrodes in alkaline media

The Dissolution and Passivation of Zinc in Concentrated Aqueous Hydroxide

Film Formation and Hydrogen Evolution on the Alkaline Zinc Electrode

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