Paul Stonehart

The influence of platinum crystallite size on the electroreduction of oxygen

Abstract The influence of platinum crystallite size on the electrocatalytic reduction of oxygen molecules in both hot phosphoric acid and sulphuric acid has been examined. It becomes obvious that when the intercrystallite distance is greater than an average of 20 nm, the apparent specific activity is fully achieved for all electrocatalyst dispersions, and that the crystallite size effect is not truly dependent on the dimensions of the platinum crystallites but is dependent on the intercrystallite distance. The crystallite size effect reported previously is not obtained in the present work by using high surface area carbons as the supports for highly dispersed platinum crystallites. The surface area of the carbon support required in order to obtain the fully active Pt crystallites in various fine sizes is indicated for different platinum loadings.

High platinum electrocatalyst utilizations for direct methanol oxidation

Abstract The influence of platinum crystallite dispersion on the electrocatalytic oxidation of methanol in sulphuric acid has been examined with different carbon black supports. There are no platinum “crystallite size” effects, even for crystallites as small as 1.4 nm in diameter, which corresponds to ca. 70% dispersion of the platinum. The mass activity increased proportionally with the specific surface area of the platinum crystallites. No inter-crystallite distance effect for platinum on the catalytic activity was found either, unlike the electroreduction of oxygen found previously. Therefore, increasing the dispersion of platinum on carbon surfaces is a significant factor for achieving a much higher catalytic activity of methanol oxidation than the present level.

Polymer solid-electrolyte composition and electrochemical cell using the composition

The polymer solid-electrolyte composition according to the present invention comprises a polymer solid electrolyte selected from the group consisting of perfluorocarbon sulfonic acid, polysulfones, perfluorocarbonic acid, styrene-divinylbenzene sulfonic acid cation-exchange resins and styrene-butadiene anion-exchange resins, and 0.01-50% by weight of fine particle silica and/or fibrous silica fiber relative to the weight of the polymer solid electrolyte.

Characterization of a Porous Electrode in a Zinc Chlorine Battery

This paper reports parameter estimation used to evaluate the performance of the flow-through porous electrode of a zinc chlorine battery. A comprehensive mathematical model was used with optimization techniques and experimentally generated polarization curves for in situ measurement of model parameters such as specific surface area, porosity, exchange current density, and the apparent cathodic transfer coefficient . The sensitivity of the model to the model parameters was analyzed and confidence limits of the calculated parameters were determined. The calculated model parameters were compared with available literature values. The model predicted most of the experimental data within 10%, and the parameter estimations were not violated. The parameter estimation technique allows for evaluation of the changes in electrode structure induced by battery cycling , whenever polarization curves over a large number of battery cycles can be obtained. This provides an opportunity for evaluating electrode degradation which takes place over long periods of time.