where n is the number of electrons transferred in the catalytic cycle, A is the electrode surface area, D is the diffusion coefficient of the catalyst (typically assumed to be equal to the diffusion coefficient of the substrate), and kobs is the observed rate constant (kobs = kcCsub). The need for the values of D, A, and Ccat can be removed by dividing equation 3 by the Randles-Ševčík equation (equation 4):