Unlike earlier reports, our present CO2-to-CO electrolyzer design concomitantly displayed close to 80% CO2 utilization efficiency, 40% single pass conversion to CO, 40% total energy efficiency, EE, and an uniquly low  stoich value of 1.2, which translated into molar CO ratio of 70% in the exit flow. Such CO-rich mixed feeds offer superior C2+ production rates when coupled to a second CO2 conversion electrolyzer tandem cell .