Sustaining Electrooxidation of Concentrated Thermo-Sensitive Biomass Feedstocks by Temperature-Mediated Kinetic and...

The inherent thermo-sensitivity of biomass feedstocks often leads to side reactions (e.g., condensation) during biomass upgrading. Electrooxidation of biomass feedstocks offers a sustainable and mild route for synthesis of value-added chemicals. However, non-Faradaic side reactions still occur in alkaline electrolytes, which severely compromise product selectivity and operational stability at high feedstock concentrations, remaining a critical obstacle for practical implementation. Herein, we propose a temperature optimization strategy for efficient and stable electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) on a designed superhydrophilic nickel-based catalyst. Especially, at 10 °C the yield and Faradaic efficiency of FDCA exceeded 94% at a high HMF concentration of 1.6 M (20 wt.%), accompanied by stable performances for at least 480 h under industrially relevant current densities. Conversely, electrocatalytic performances degraded rapidly over time at 25 °C. Lowering temperature prevents electrode fouling by inhibiting non-Faradaic side reactions, thus preserving catalytic site accessibility. Furthermore, the adsorption of OH^-, identified as the rate-determining step, is promoted by reducing temperature in the adsorptive competition with HMF, sustaining efficient β-Ni(OH)₂/β-NiOOH redox cycle with elevated HMF concentrations. The stabilization and optimization of interfacial microenvironment enable durable and efficient electrooxidation of HMF and other thermo-sensitive biomass derivatives to desired organic acids.