Figure shows the average full cell potential for each current density. The electrolyte conductivity is strongly affected by the electrolyte concentration and is reflected in a 50-150 mV shift in the cell potential when the electrolyte concentration changes by a factor of 10. In Figure , the average Cs + content is displayed at the catalyst layer for 0.01 M and 0.1 M CsHCO3 at each current density. A higher Cs + content is always observed at a higher current density. The local Cs + content reaches a maximum intensity of 25 arb.u. for 0.01 M CsHCO3 and of 40•arb.u. for 0.1 M CsHCO3 at 200 mA cm - 2 . Interestingly, even though there is an order of magnitude difference in the concentrations of the two solutions, their local Cs + content difference is within a factor of 2. Thus, the Cs + content within the cathode catalyst layer is mostly driven by the electric field, rather than diffusion.