pH‐dependent electrochemical oxidation of 5‐hydroxymethylfurfural: Reaction mechanism, catalyst design, and reactor design across alkaline to acidic media

Abstract The electrochemical oxidation of biomass‐derived platform molecule 5‐hydroxymethylfurfural (HMF) represents a crucial pathway for green transformation into high‐value chemicals, yet its reaction pathway selectivity, efficiency, and catalyst stability are strongly dependent on the electrolyte pH environment. Under alkaline conditions, high OH − concentration facilitates preferential aldehyde group oxidation and efficient deprotonation, enabling highly efficient synthesis of 2,5‐furandicarboxylic acid, but simultaneously induces HMF self‐degradation and complicates product separation. As pH decreases, the reaction mechanism shifts toward enhanced hydroxymethyl oxidation, leading to intermediate accumulation (such as 5‐hydroxymethyl‐2‐furancarboxylic acid, 2,5‐diformylfuran, and 5‐formyl‐2‐furancarboxylic acid) with challenging selectivity control and significantly slowed reaction kinetics. This review comprehensively examines the systematic differences in HMF oxidation pathways and surface catalytic mechanisms across the full pH range from alkaline to acidic conditions. Addressing the distinct reaction characteristics and core challenges in alkaline, near‐neutral, and acidic media, we systematically evaluate design strategies for high‐efficiency electrocatalysts and explore reactor design aspects. Future research should focus on process integration (with tailored reactor design) for energy consumption reduction in alkaline systems, targeted synthesis of diverse oxidation products in near‐neutral systems, and innovative catalyst development for acidic systems, thereby advancing the efficiency, selectivity, and practical application of HMF electrooxidation technologies across the entire pH spectrum through synergistic optimization of catalyst, reactor, and process.