is the concentration of CO 2 in saturated pure water at room temperature (obtained from Henry's law). The steady-state current densities j i from the MKM along with the bulk conditions are fed back into the transport model until convergence in j i is reached. The outputs from the multiscale model are: j i as a function of the applied potential, Faradaic efficiencies (FE), local conditions at the OHP as well as across the diffusion layer (see Figure ), and degree of rate control of kinetic elementary steps.