Pretreatment methods, platinum surfaces

The correlation between the coverage of surface platinum atoms by bismuth adatoms (Ggi) and the measured rate of 1-phenylethanol oxidation was studied on unsupported platinum catalysts. An electrochemical method (cyclic voltammetry) was applied to determine G i and a good electric conductivity of the sample was necessary for the measurements. The usual chemisorption measurements have the disadvantage of possible surface restructuring of the bimetallic system at the pretreatment temperature. Another advantage of the electrochemical polarization method is that the same aqueous alkaline solution may be applied for the study of the surface structure of the catalyst and for the liquid phase oxidation of the alcohol substrate. 

The cleaning of the electrode surface presents a very difficult problem with the platinum electrodes. Some workers recommend cleaning with dilute sulphuric acid solution, others recommend treatment with chromic acid (which, of course, oxidizes the electrode surface). Still other workers recommend pretreatment at a constant potential for a certain length of time or at a series of potentials. The best way to be followed seems to be the one best suited to the problem at hand in that logical and reproducible results are obtained. A method of pretreatment, however, must be devised before one is able to produce data to any degree of reliability. 

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