Abstract
Previous work on the theory of the cyclic voltammetric (potential sweep) method is reviewed. In cases where a multielectron reaction occurs, it is shown that simple kinetic assumptions (that all electrons are transferred in a single step or that all steps save one are in pseudoequilibrium) are likely to lead to erroneous interpretations. The most fundamental parameter is (in the irreversible case) the variation of the peak maximum potential with log sweep rate. This will enable the rate‐determining step to be located in the reaction sequence. The transfer coefficient and Temkin parameters determined from the peak shape are not necessarily those of the rate‐determining step, but those of the potential‐determining step. Results are applied to adsorbed oxygen film formation and reduction on platinum. It is shown that a two‐stage reaction occurs, with the rate constant of the first anodic step (− OH formation) falling exponentially with coverage. This is associated with a rearrangement of the surface phase, accompanied by very rapid −O formation. In the cathodic direction, the position and shape of the peak is governed by the kinetic parameters of −O reduction, whereas −OH reduction is rate‐determining. There is evidence that the heterogeneity factor and the free energy of the −O reduction step depend on coverage [cf. Ref. (6)]. The same mechanism may apply to palladium and rhodium and perhaps also to gold.