The heterogeneous diffusion rate constant defined for the case of the limiting current. A more general definition in terms of the electrode current densities is: \[k_{\text{d}}=\frac{j\ \nu }{n\ F\ (c_{\text{e}}- c_{0})}\] or \[k_{\text{d}} = \frac{j\ \nu \ (1- t_{\text{B}}\ n\ \nu ^{-1}\ z_{\text{B}}^{-1})}{n\ F\ (c_{\text{e}}- c_{0})}\] where j is the electrode current density, ν is the stoichiometric number, n is the charge number of the electrode reaction, F is the Faraday constant, ce is the interfacial concentration, c0 is the bulk concentration, t B is the transport number of species B, and z B is the charge number of species B.