Effect of the reagent orientation at the electrode-solution interface on the electrochemical kinetics

Possible dependences of kinetic parameters of electrochemical reactions of electron transfer on the orientation of particles of the reagent in the nea r-electrode layer are considered. The general principles pertaining to the description of the rate of processes for particles of nonspherical forms wi th and without a nonuniformly distributed charge are discussed in the frame work of a model that allows for a set of possible orientations of the reage nt. As an illustration, estimates are presented of effective rate constants for the reaction of reduction of a plane square complex of the type [PtCl4 ](2-). It is shown that the assumed alteration of the angular distribution of the reagent in a wide interval of charges of the electrode may induce, i n a certain potential interval, an inhibition of the process that, in princ iple, cannot be counterbalanced by an increase in the supporting electrolyt e concentration even if the reacting particle is localized in the diffuse p art of the electrical double layer. Using the [Cr(edta)](-) complex as an e xample, it is demonstrated that the orientation effects may be calculated u sing not only the data on a microscopic charge distribution but also employ ing the data on the magnitudes of dipole moments of particles.