Assuming a combined catholyte and anolyte thickness of 3 mm, for example, it is clear that certain electrolytes will cause prohibitive ohmic losses (Fig. ). The 0.1 M KHCO3 electrolyte used in the majority of the highest selectivity C2H4 studies, for instance, results in heating losses of 6 V at 200 mA/cm 2 , five-fold larger than the thermodynamic cell potential when using an oxygen-evolving anode (Fig. ). Such a low conductivity electrolyte can then never be used in a functioning system unless the electrolyte pathway between the anode and cathode is eliminated or greatly reduced, as in the case of membrane electrode assemblies (Fig. ). These ohmic drops also put into perspective how other cell losses may be more influential than further decreases to cathode overpotentials. It is worth noting that the result in Fig. becomes even more pronounced when the presumed even higher current densities needed for multi-carbon products such as C2H4 are considered. Finally, separate from our discussion motivating the testing of catalysts at elevated current densities, this result highlights the need to test catalysts in higher conductivity electrolytes to see the effect that a higher concentration of supporting ions may or may not impact a catalyst's activity.