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|Title: ||Aspects of zinc electrochemistry|
|Authors: ||Morgan, P.C.|
|Issue Date: ||1983|
|Publisher: ||© P.C. Morgan|
|Abstract: ||The electrochemistry of porous, and planar zinc electrodes has
been examined in connection with the application of zinc in electrochemical
power sources. Planar, horizontal, upward-facing zinc electrodes
have been galvanostatically oxidised in a convection-free system
containing KOH under a series of different conditions. Many additives have been reported to increase T, but in
the convection-free system no significant increase has been observed.
Porous electrodes have been oxidised in the same system. The
formation of duplex films has been confirmed optically, and the
expansion of an oxidising electrode has been followed using a travelling
microscope. A reaction plane parallel to the external surface has
been observed penetrating the electrode.
Rotating disc electrode experiments have been used to study the
oxidation of zinc in a number of electrolytes. In NaC104 semiconducting
films were formed. In KOH a solution soluble region was
identified. Linear sweep voltammograms were recorded in KOH, KOH
containing polymaleic acid, and NaCl04/ZnBr2 solutions. The techniques
have been combined to show that the cathodic peak observed on reversing
an anodic sweep in KOH is due to the reduction of soluble species from
a Type I film, rather than reduction of a solid state film.
The A. C. impedance of zinc in KOH, and in KOH with a carboxymethylcellulose,
has been measured, and a theory proposed to explain the experimental results.
A practical cell has been modelled. The current distribution
along the porous zinc electrodes has been measured. Cadmium ring counter electrodes have been developed of greater
recoverable charge capacity, and longer cycle life than the zinc electrode.
These have been assembled in a 3-tier stack with separators and zinc
electrodes in the central cavity. This complex cell was cycled under
electrolyte-starved conditions, and the current passing in each segmental
ring has been measured, and the charge recoverable calculated. The
differences between oxidative and reductive charge in each-cycle was
attributed to zinc relocation. An electrode which only partially
filled the cavity showed rapid shape-change. Electrodes that filled
the cavity showed an expansion above the level of the rings during
cycling, and ultimately failed due to oxygen evolution.
The implications of these researches to contemporary porous zinc
electrode technology are discussed.|
|Description: ||Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Chemistry)|
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