Efficient Electrooxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid in a Weak Alkaline Medium Enabled by Interfacial OH⁻ Enrichment

Abstract Developing electrooxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) in a weak alkaline medium can potentially inhibit HMF degradation to humins and thus mitigate carbon loss that is encountered in strong alkaline media; however, the activity is often compromised under low OH − concentration. Herein, by incorporating chromium oxide (CrO x ) as a hard Lewis acid onto CoO x surface (CoO x –CrO x ), HMF electrooxidation activity is largely boosted in a 1 m carbonate buffer (pH 11), including higher FDCA Faradaic efficiency (from 41% to 90%), selectivity (from 33% to 92%), and yield (from 28% to 89%). The electrolysis under the weak alkaline medium can tolerate high HMF initial concentration (100 m m ), showing higher carbon balance (97%) compared with that in strong alkali (≈70%). Experimental data reveal that CrO x accelerates OH − migration from bulk to the electrode surface and enriches OH − at the electrode–electrolyte interface, enhancing catalyst reconstruction and reaction intermediate conversion, thus promoting the activity. Furthermore, the interfacial OH − enrichment strategy is demonstrated effective for other weak alkaline medium and for other biomass‐derived molecule (ethylene glycol and glycerol) electrooxidations. This work demonstrates that hard‐Lewis‐acid‐induced OH − enrichment dynamically optimizes interfacial microenvironment, establishing a new design principle for efficient electrocatalytic systems under weak alkaline conditions.