Based on these results, we propose that the active site for eCO 2 R consists of a microenvironment including both the surface sites on Ag and a partially dehydrated cation present in the vicinity of the reaction plane (less than 5.7 Å, see Figure ). We include this proposed active site by accounting for the transport of the cation from the OHP to the vicinity of the electrode as an elementary step in the microkinetic model (MKM). To obtain the kinetic constants associated with the cations' transport, we first performed AIMD simulations with Li + , K + and Cs + on Ag(111) in the presence of CO 2 -.