represents the rate order of species i in the reaction to form species j and is constrained by its relationships to the transfer coefficients, as given by Equations S8-10. Here, 𝑎 5 represents the activity of species i locally at the electrode surface, as calculated by the reaction-transport simulation, and 𝑎 5 /012 represents the activity of species i in the bulk electrolyte. The terms involving the ratio of the surface and bulk activity account for mass-transport and concentration gradients within the boundary layer. 𝜂 4,5 is the surface overpotential for a given electrochemical reaction defined in Equations S15 and S16 in the SI. A detailed description of the physics employed in the model, as well as a generalized derivation of the kinetic model, can be found in the SI, Sections S1-3.