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

Abstract

In a membrane electrode assembly (MEA) electrolyzer based on a cation-exchange membrane, achieving an efficient and stable CO 2 reduction reaction (CO 2 RR) 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 CO 2 RR 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 CO 2 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 CO 2 RR operation. Our approach of reverse osmosis to balance cations and water is viable for industrial applications because pressurized CO 2 and MEA systems are efficient processes that can be commercialized.

Elevated temperature and pressure driven ampere-level CO2 electroreduction to CO in a membrane electrode assembly electrolyzer

“…To date, most CO 2 RR-MEA cell studies have been conducted under ambient conditions, with only limited reports on investigating pressurized MEA cells. 21,22 In these studies, pressure was typically applied only to the cathode side, leading to gas crossover through the membrane due to pressure imbalances when the differential exceeded 6 bar, ultimately resulting in decreased performance. 23…”

Water Management in Zero-Gap CO2 Electrolyzer with Forward Bias Bipolar Membranes

“…Examples include more hydrophobic gas diffusion layers (GDLs) 15 or catalyst layers (CLs), 16 more permeable microporous layers (MPLs), 17 a thinner membrane, 16 a modified membrane, 18 a wet CO 2 feed, 11,19 pulsed operation, 20 or pressure gradients. 21 Another option is to use bipolar membranes (BPM), which consist of two oppositely charged ion-exchange layers, thus allowing a pH gradient between the electrodes. The cathode is alkaline when the BPM is applied in forward bias, which favors a high faradaic efficiency for CO 2 reduction.…”

Identification of Degradation Reasons for a CO2 MEA Electrolyzer Using the Distribution of Relaxation Times Analysis

“…Producing high-value chemicals and feedstocks through electrocatalytic CO 2 reduction (ECO 2 R) driven by renewable energy can close the carbon cycle and mitigate global warming. − Significant progress has been made in the ECO 2 R field over the past few decades through the integration of catalyst design and reactor engineering. − However, achieving industrial application requires a current density of at least 200 mA cm –2 . Membrane electrode assembly (MEA) is a promising approach to meeting this requirement, making it a crucial route for the industrialization of ECO 2 R. , MEA utilizes gas diffusion electrodes that provide abundant three-phase boundary sites for electrochemical reactions, enabling sustained high-current operation. , Furthermore, as zero-gap cells, MEA minimizes the ohmic resistance between the anode and cathode, thus preventing ohmic polarization at high currents. − Nevertheless, the performance degradation of ECO 2 R over prolonged MEA operation remains a critical challenge. − Therefore, the development of in situ, nondestructive monitoring techniques is urgently needed to detect and diagnose the causes of the failure, which will provide the foundation for addressing ECO 2 R performance degradation issues.…”