We show that the TMA + cations in the AEM inherently stabilize the CO 2 -and COOH polarized reaction intermediates (Figure ). In comparison to K + , the TMA + based microenvironments lead to weaker CO 2 -adsorption energy (less stable by 0.1 eV) and higher PCET barriers by at least 0.1 eV. This can be attributed to the lower charge density and larger distance (¿4.5 Å) of the TMA + ions from the surface as compared to the inorganic cations. Another important distinction between TMA + and K + is that the positive moiety does not need to be transported to the surface from the double layer, as its concentration is fixed by the characteristics of the membrane. To investigate how fixing the TMA + moieties on the membrane affects current densities as compared to freely moving moieties in a liquid electrolyte, we also considered the N(CH 3 ) 4 HCO 3 buffer. Our AIMD simulations show that TMA + ions in water are already present at a distance of ∼4.5 Å from the surface, which is close to the OHP distance considered in this study . Therefore, the surface coverages are directly estimated, without considering a water coordination shift, by assuming proportionality with the steric limit concentration of TMA + (4.2 M). The peak potential for TMA + current densities is shifted to more negative potentials compared to K + . This shift can be explained by the higher PCET barriers for TMA + microenvironments: the rate for the first PCET is relatively lower compared to K + at intermediate potentials, and higher potentials must be applied for it to compete with the