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.