Coupling these different length scales via multiscale modeling can provide a robust way to optimize microenvironments. Consistency in the assumptions adopted across lengthscales is paramount when coupling surface reaction kinetics with transport and homogeneous reactions occurring in the electrolyte . The first multiscale model of eCO 2 R included microkinetics with DFT-derived kinetic constants paired with a continuum transport model. By evaluating different pathways for CO formation on Ag(110), a reaction mechanism involving CO - 2 as an intermediate and H 2 O as a proton source was proposed, which captured the experimental trends in current densities as a function of CO 2 partial pressure. A subsequent study considering cations and size exclusion effects at the transport level and adsorption energies of eCO 2 R intermediates with a double layer charging (mean-field) model could reproduce the trends across monovalent cations on Ag and Cu and the observed Tafel slopes on Au(211) . In these cases, the effect of the cation was fundamentally electrostatic and coupled the macroscale to the atomistic level through the surface charge densities. However, surface-enhanced spectroscopy measurements suggest that considering only non-bonding electric field effects might be too simplistic, and local interactions between the cation and the key intermediates need to be explicitly taken into account.