Physico-chemical testing adsorption

The number of remaining parameters in (27) amounts to 8 the molecular mass of the coke, Mg, 2 frequency factors and 2 activa tion energies, 3 adsorption equilibrium constants, considered to be independent of temperature They were determined by non linear regression. F-tests were applied to the fit of the equation to the experimental data and t-tests to the parameter values The fit was excellent at 823 K, but less satisfactory at 873 K It could be improved and plausible values for the physico-chemical parameters could be obtained if two stages were considered in the rate of growth of coke instantaneous up to a certain intermediate size and finite beyond. 

Modification of the electrode started with academic studies on physical and chemical adsorption, i.e., with the appearance of fundamental researches on adsorption of different species on electrode surfaces, both under polarization and at open circuit potential [3]. The properties of similar chemically modified electrodes , in which the modifier consists of a monolayer of a variety of chemical species with different characteristics, possessing (or not) particular properties, were initially studied in a purely electrochemical context, aimed at the collection of fundamental physico-chemical data. A small group of electrochemists were among those involved in these basic studies, envisioning the perspectives opened by the novel systems. In the first, really fascinating, work with similar monomolecular layers, cobalt porphyrin and phthalocyanine, as well as deliberately synthesized dicobalt face-to-face porphyrins were adsorbed on Pt or C surfaces to catalyze molecular oxygen reduction [4]. However, similar systems were not always used or adequately tested in proper amperometric sensing by researchers more interested in electroanalysis dicobalt face-to-face porphirins still constitute a rare example of tailored materials for selective amperometric detection. 

A somewhat slow but controllable impregnation method with the dipping of support into an excess of aqueous solution of (NH4)3[Fe(C204)3].xH20 is adopted to prepare well-dispersed or monolayer-type ferric oxide on various supports. Other methods with the same and other conditions are also used to make a comparison among them. The influences on the adsorption process are investigated and the suitable conditions are determined for the different supported systems. Extensive characterization has been done on the physico-chemical properties of these systems. The catalytic performances for different test reactions are also carri out on the various supported systems with distinctly different dispersions. 

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