We now compare the three predicted limiting exit flow ratecurrent relations to the experimental data (Figure ). The dashed lines denote the limiting cases for perfect faradaic efficiencies according to Supplementary Figure . The solid lines are the experimental values. At low loadings (1.0 mg cm -2 , ~95% FECO) NiNC-IMI displayed an almost ideal flow depletion pattern over a wide current range, perfectly matching the predicted CO 3 2-throughplane transfer at FECO=100% , Figure . By contrast, cells with higher catalyst loadings showed gradual volume surplus, attributed to a rising FEH2 and OH -crossover. Conversely, impact of the NINC-PANI loading was minor, never followed a limiting mass transfer case, and showed an increasing crossover of OH -over CO 3 2-, Figure .