Redox‐Mediated CO₂ Electrolysis for Recovering Transmembrane Carbon Loss

Abstract CO 2 electrolysis in alkaline media presents advantages by suppressing the competitive hydrogen evolution reaction (HER) and enhancing the CO 2 reduction selectivity. However, it suffers from the carbonation issue, leading to substantial carbon loss due to CO 2 transmembrane transport. To tackle this issue, we here put forward a redox mediator (RM)‐coupled electrolysis strategy. By integrating a highly reversible redox couple, this approach spatially separates the cathodic CO 2 reduction and the anodic oxygen evolution reactions (OERs) into two electrolyzers, thereby enabling the recovery and reuse of transmembrane CO 2 . Anthraquinone‐2,7‐disulfonic acid (AQDS) was chosen as the redox mediator owing to its suitable redox potential, excellent electrochemical reversibility, high solubility, and nontransmembrane shuttling characteristics. It allowed the RM‐coupled electrolysis system to operate continuously at 100 mA/cm 2 , maintaining a high Faradaic efficiency (FE) for CO 2 ‐to‐CO conversion consistently around 90%, while effectively capturing the transmembrane CO 2 . This proof‐of‐concept demonstration validates the feasibility of RM‐coupled electrolysis and highlights its significant potential to advance the practical application of CO 2 electrolysis.