Electrochemical reaction of CO2 to CO on a catalyst coated cation exchange membrane enabled by ammonium proton shuttling

摘要

CO2 reduction (CO2RR) can convert CO2 into feedstock for the chemical industry. In aqueous CO2 electrolysis a key challenge is how to combine the CO2 educt with a neutral or alkaline electrolyte and achieve a stable cell operation. We propose a novel cell design and operation mode based on a catalyst coated cation exchange membrane: a cationic acid (NH4+), with a volatile conjugate base (NH3), replaces the protons usually present for ion transport. The approach avoids a high proton concentration at the cathode catalyst while still removing all products within the gas phase. In this paper different cell concepts are investigated to identify a pathway to a stable, efficient and scalable operation mode. In a completely novel cell design a FECO > 50% was already maintained for over 35 h at 50 mA cm−2, and at 200 mA cm−2 a cell voltage of 3.6 V (FECO > 60%) was achieved. Surprisingly, ammonium oxidation at the anode was fully supressed under the reaction conditions.