High molar CO ratios in the exit feed benefit the catalytic conversion rates and product efficiencies in the downstream electrocatalytic CO-to-C2+ reactions in cell 2 of Figure . This work will address this unmet need highlighting an efficient precious metal-free "CO2-to-CO" electrolyzer cathode design, along with a novel diagnostic approach of its catalytic and mass transport characteristics. From this analysis, we diagnose the effectiveness of in-plane and through-plane ionic transport and validate our conclusions by microscopic analysis.