In this study, we resolve the species concentrations and potential profiles in the EDL of a syngas (CO and H 2 ) producing CO 2 ER system by self-consistently solving the migration, diffusion and reaction phenomena in a CO 2 saturated aqueous electrolyte facing a planar cathode (see schematic in Figure ). We do this by numerically solving the generalized modified Poisson-Nernst-Planck (GMPNP) set of equations which include the effect of volume exclusion due to the solvated size of solution species . Using the GMPNP equations, we demonstrate that the inclusion of migration in the mass transport of species provides a drastically different picture of the catalyst reaction environment as compared to reaction-diffusion models. By comparing with a PNP system, where molecules are considered as point species without volume, we show how inclusion of size of solvated solution species is important to derive physically consistent concentration profiles at high operating potentials. The effect of volume exclusion in the GMPNP model results in a diminishing of CO 2 concentration from the EDL at high applied potentials providing strong evidence of many-body correlations playing an important role in the transport of CO 2 to the catalyst surface. The resistance to the transport of CO 2 to the catalyst surface through a densely packed layer of solvated cations can potentially play a role in the activation mechanism of the CO 2 molecule. Yet another important consequence of the interaction of the electrostatic forces in the EDL with charged species is a considerable drop in the pH and OH -concentration for a distance of up to 5 nm from the outer Helmholtz plane (OHP). This has significant repercussions for the CO 2 ER system especially from a mechanistic view-point, while requiring us to provide greater definition to what is defined as the 'local reaction environment'. Finally, we compare the properties of the EDL for different alkali metal cations and look at the results in view of the existing experimental evidence.