Direction of oxygen evolution reaction electrocatalyst evaluation for an anion exchange membrane CO2 electrolyzer

Abstract

CO₂ electrolysis in membrane-electrode assemblies (MEAs) has come up one step closer to commercialization through compact cell design and high-current operation. However, while both cathodic and anodic reactions significantly affect the overall cell efficiency, the anodic oxygen evolution reaction (OER) has received much less attention compared to the cathodic CO₂ reduction reaction (CO₂RR). More importantly, OER electrocatalysts for CO₂ electrolysis are being developed independently of system design, despite their interconnected nature. Since the aqueous testing systems in which OER electrocatalysts have been developed do not reflect the complex local anodic environment inside an anion exchange membrane CO₂ electrolyzer (AEMCE), electrocatalysts sensitive to local chemistry may have been optimized for incorrect operating conditions. Based on a comprehensive understanding of the local anodic environment inside the AEMCE, in this perspective, we scrutinize the limitations of conventional OER electrocatalyst development resulting from the discrepancy between aqueous testing systems and the existing MEA-type systems. To bridge these gaps, we suggest three electrocatalyst evaluation platforms that integrate reference electrodes to existing AEMCEs for reliable and genuine OER electrocatalyst assessment.