THE FRUMKIN MODEL APPLIED TO THE ADSORPTION PROCESS OF BENZENE ON A PT ELECTRODE FROM SULFURIC-ACID-SOLUTIONS

The electroadsorption of benzene on a polycrystalline Pt electrode fro m 0.5 M H2SO4+ x M C6H6 solutions was studied as a function of the ben zene concentration,time and potential of adsorption. It was observed t hat the maximum adsorption takes place in the double layer region, eve n though the adsorption process can also occur in the hydrogen region. At the potential of maximum adsorption the experimental results showe d that benzene molecules are strongly adsorbed on the Pt surface, each one occupying about 7.6 +/- 1 accessible Pt sites and an average surf ace of 43 Angstrom. The dependence of the coverage degree, theta(b), O n the adsorption time and benzene concentration was analyzed by means of the Frumkin adsorption model. However, in order to explain both the adsorption process and the value of the Frumkin interaction factor a, the quasichemical approximation developed by Guidelli for the Frumkin isotherm was used.