Achieving Stable Paired Electrolysis of Captured CO ₂ and 5‐Hydroxymethylfurfural (HMF) via Tuning Anolyte Composition and Anode Surface

Abstract Coupling CO ₂ electrolysis with biomass oxidation in a single reactor enhances the economic viability of electrosynthesis. However, the use of highly basic anolyte for alcohol oxidation poses significant challenges, reducing operational lifespans. Herein, a solution is presented using triethylamine (TEA) as both a CO ₂ ‐capturing agent and pH buffer for the oxidation of 5‐hydroxymethylfurfural (HMF), replacing traditional hydroxide salts. A tailored triethylamine‐carbonate solution mitigates the challenges posed by basic electrolytes and enhances oxidation reactivity of HMF. Furthermore, the coating of an anion‐conducting ionomer on the anode surface improves pH buffering and improves reactant adsorption. These advancements enable stable HMF oxidation without anolyte refreshment, even as the pH approaches neutral, allowing for the co‐production of synthetic gas and 2,5‐furan dicarboxylic acid (FDCA), a key plastic precursor, over 150 h in a membrane‐electrode assembly reactor. This finding demonstrates a viable pathway for integrating reactive carbon capture and oxidative conversion of biomass for electrosynthesis.