ANALYSIS OF IRREVERSIBLE OXIDATION WAVE OF ADSORBED CO AT PT(111), PT(100) AND PT(110) ELECTRODES

The oxidation wave of CO preadsorbed at 50 mV on Pt(111), (100) and (1 10) electrodes in phosphate buffer solution of pH 3 was observed as a function of the sweep rate. The sweep rate dependence of the peak curr ent and peak potential, as well as the form of the wave, were examined on the basis of the Gilman mechanism that the electron transfer from a complex consisting of CO and oxygen containing species is the rate-d etermining step. An electron transfer step from CO itself was excluded . The peak current and peak potential analyses and the wave simulation gave the same value for DELTAf, the change in the interaction energy during the formation of the activated complex from the reactants. DELT Af was sweep-rate and surface-structure dependent. The nature of DELTA f was discussed.