Fritz G. Will

Electrochemical Oxidation of Hydrogen on Partially Immersed Platinum Electrodes II . Theoretical Treatment

The mechanism of the anodic oxidation of molecular hydrogen on partially immersed platinum electrodes in acidic solutions, serving as an idealized model for a gas diffusion electrode, has been treated theoretically. The mechanism, which earlier experiments had suggested, consists of the slow diffusion of molecular hydrogen through the upper edge of the electrolyte meniscus and a thin liquid film covering the electrode surface above the intrinsic meniscus. On the basis of this model, the relationship between current and applied potential is derived which agrees with experimental data over a potential range from zero to 1.8v. The relative contributions of meniscus and film to the total current are calculated. The reaction takes place mainly at a few tenths of a millimeter length of the electrode close to the upper meniscus edge. The true current density at this narrow band and the thickness of the liquid film are calculated. The surface diffusion of hydrogen atoms as rate‐determining transport mechanism has also been treated, and it is shown that the results of this treatment are not in agreement with the experimental data.

Parametric Study of Zinc Deposition on Porous Carbon in a Flowing Electrolyte Cell

X-ray radiography coupled with high resolution optical densitometry, as well as optical and scanning electron microscopy, was employed to study the effect of pivotal zinc deposition parameters on the zinc morphology within a porous C foam electrode. Deposition was carried out in zinc-bromine and zinc-zinc cells with circulating electrolyte. Results on the effects of flow rate, substrate thickness, current density, and electrolyte composition on zinc distribution in the substrate and on its surface are described. This study has shown that in the absence of organi inhibitors, very nonuniform zinc deposition occurs within the porous electrode. This zinc deposition corresponds to the nonuniform primary current distribution dominated by ohmic resistance. This study has led to the conclusions tha high electrolyte flow rates, moderate current densities, and thick foams all aid in producing increasingly uniform zinc deposits. The most beneficial effects on the zinc morphology, however, were obtained by adding to the electrolyt a dendrite inhibitor-solubilizer combination consisting of certain fluorosurfactants and butyrolactone.

Charge‐Discharge Behavior of Polyacetylene Electrodes

The charge-discharge and open-circuit behavior of polyacetylene electrodes, p-doped with BF4, is examined.Discharge curves for controlled current are interpreted quantitatively in terms of a model involving slow dopant diffusion and slow discharge at the polymer/electrolyte interface. The open-circuit potential is measured as a function of mean dopant level. It is shown that, due to the slow dopant diffusion, no steady-state potentials are attained. The coulombic efficiency of pristine polyacetylene electrodes in identical states of doping is determined as a function of discharge current. Discrepancies among results of different authors are related to different dopant states near the polymer surface. A quantitative relationship between efficiency and current is derived which is shown to be valid for small polarizations and short discharge times. 14 references.

Rotating Ring‐Disk Electrode Studies of Cadmium in Alkaline Solution Nucleation and Growth of Cadmium Hydroxide

The rotating ring-disk electrode method has been applied to study several new aspects of the oxidation mechanism of cadmium in concentrated potassium hydroxide solutions

An X-ray radiography-densitometry technique for the quantitative determination of metal deposit profiles

The application of x-ray radiography in conjunction with high resolution optical densitometry for the quantitative determination of metal deposit profiles parallel and perpendicular to the substrate surface is described. The principles of the technique and the range of its applicability are discussed. The technique is applied to the study of zinc deposition on highly porous carbon foams from circulating aqueous zinc bromide solutions. The effect of substrate pore size on the zinc distribution is explored. Zinc is found to deposit predominantly on the porous substrate/electrolyte and substrate/current collector interfaces. Smaller pore size favors smoother and more uniform deposits throughout the substrate.