Cs + based buffers are the best performing electrolytes towards eCO 2 R on Ag(111) in the explored potential range due to a combination of favorable atomic scale and transport effects (Figure (f)). Additionally, CsHCO 3 has a solubility limit of 10.78 mol/1L H 2 O [52], therefore the better performances for Cs + are coupled with a reduced risk of carbonate precipitation. The CO current density in Li + based buffers are within an order of magnitude of the case of K + at low applied voltages (E <-1.1 V RHE ), while at higher potentials the transport limitations of Li + are prevalent due to the larger hydrated size and K + shows current densities two orders of magnitude higher than Li + .