Publications

Ambient heat treatment atmospheres have been found to have significant effect on the oxygen reduction catalytic activity of Co tetraazaannulene and its dibromo derivative. Two macrocyclic chelates were absorbed on acetylene black carbon from DMF (dimethyl formamide) solutions, then heat treated in each of the following environments: N2, Ar, vacuum and nitrogen passed over heated copper turnings. Electrodes were prepared by pasting the catalyst mixed with a Teflon slurry onto a carbon cloth. The catalytic activity was evaluated from steady state current vs voltage measurements for the electrochemical reduction of oxygen in 4 N H2SO4. The results indicate that the activity of the two chelates is influenced by the ambient atmospheres of heat treatment. ESCA examination of the adsorbed Co tetraazaannulene dibromide on the acetylene black carbon heat treated in N2 and vacuum indicated evidence of bonding with the carbon surface for the former and possible polymerization of the catalyst on the surface for the latter. © 1985.

A theoretical model is presented for a Teflon-bonded carbon porous diffusion electrode used for oxygen reduction in alkaline solution. The model is of the flooded agglomerate type and is extended to allow parameter estimation by regression analysis of polarization data. The data presented are for a Teflon-bonded carbon electrode (silver catalyst) tested in a laboratory scale cell using 3.5M (150 kg/m3) sodium hydroxide solution at 348 K with three different oxygen feed mole percents: 10, 20, and 100%. Regression indicates that the diffusion processes in both gas and liquid phases contribute significantly to polarization. © 1985, Taylor & Francis Group, LLC. All rights reserved.

Electrochemical corrosion rates of 70Cu-30Ni alloy have been measured in oxygenated 0. 5M NaCl and in synthetic seawater by the Tafel extrapolation procedure using a rotating disk electrode system. Corrosion rate measurements of freshly polished 70Cu-30Ni alloy in 0. 5M NaCl and in synthetic seawater indicated that the alloy corrodes differently in the two media and that the corrosion rate is much higher in 0. 5M NaCl than in SSW. In the former electrolyte, the alloy corrodes via the formation of a soluble corrosion product, and in the latter, via a passivation process. The corrosion current and corrosion potential in 0. 5M NaCl were dependent on the rotation rate of the electrode, as expected, while in SSW, both quantities were independent of rotation rates because a surface kinetic process rather than a diffusion process controls the corrosion mechanism.

A technique for chemically bonding and polymerizing organometallic chelate catalysts on a carbon substrate has been developed, with the objective of improving catalyst activity and stability for the reduction of oxygen in acidic electrolytes. Acetylene black carbon was chemically modified by bonding with polymerized iron tetrachlorophthalocyanine catalyst, followed by heat treatment. An electrode made with this catalyst showed significant improvement in activity and stability as compard with a similar unmodified catalytic electrode. © 1984.

The oxygen evolution reaction has been investigated on a number of electrodes which are electrocatalysts for the chlorine evolution reaction, by making measurements in NaClO4 solution. Steady state current-potential and impedance-potential measurements, obtained using automated equipment, have been used as the preferred experimental method. Analysis of the impedance has been undertaken by means of curve fitting, and the resulting parameter curves of the double-layer capacity, the charge transfer resistance, and the electrolyte ohmic resistance displayed as a function of potential. Some speculation is made about the interpretation of the parameter curves. The ohmic loss parameter, Rw, is used to correct the potentials to the true values. In comparison to some other gas evolution reactions, such as hydrogen and chlorine, Rw does not depend strongly on potential. The corrected log i-E curve is also considered. It is suggested that a more complete picture of the electrical performance of these electrodes can be obtained by using these electrochemical methods. © 1984.

A number of electrodes which are catalysts for the chlorine evolution reaction have been investigated using steady state current-potential and impedance-potential measurements. Electrodes which show similar overvoltages for the chlorine evolution reaction in technical tests show large differences when subjected to this kinetic approach. © 1984.

Darby s model of a hydrophylic, gas-fed porous electrode is reviewed and extended. The review includes aspects of Darby s model which were previously not available in the open literature, and the extensions consist of including previously neglected terms in the governing differential equations, fractional reaction orders in the current density-overpotential expression, and mass transfer coefficients to account for mass transfer resistance of the reactants to the faces of the porous electrode. The model is used to predict quantities of interest for oxygen reduction in an acidic aqueous solution in a porous carbon electrode.

An experimental analysis of the Formula redox reaction in a porous back fed ruthenium‐coated titanium electrode is described. A mathematical model of the steady‐state process is presented. Nonlinear regression of the model against the experimental data gives physically meaningful parameter estimates; these parameters and the model provide a design equation for the porous electrode current as a function of specific surface area, bulk Formula concentration, average total overpotential, and the Reynolds number. The design equation shows that the back fed electrode could reduce the loss of Formula across the separator and the ohmic loss in a Formula battery.