Deriving an Efficient and Stable Microenvironment for a CO2 MEA Electrolyzer by Reverse Osmosis

In a membrane electrode assembly (MEA) electrolyzer based on a cation-exchange membrane, achieving an efficient and stable CO2 reduction reaction (CO2RR) is challenging because the transport of protons, cations, and electro-osmotic water from the anode changes the balance of ions. Herein, we derived a microenvironment for stable and efficient CO2RR performance by using two strategies. First, a mixture of carbon and anion-exchange ionomer buffer layers is used to hold cations while managing water in local alkaline media. The second strategy involves pressurizing only the cathode side, resulting in a high local CO2 concentration and enhancing the reverse osmosis phenomenon. The synergistic effects of these two strategies create an efficient microenvironment by managing water and cations, leading to a stable and efficient CO2RR operation. Our approach of reverse osmosis to balance cations and water is viable for industrial applications because pressurized CO2 and MEA systems are efficient processes that can be commercialized.