Robust nickel-cobalt oxyhydroxide electrocatalysts for the sustainable and efficient electrochemical valorization of 5-hydroxymethylfurfural at near-neutral pH

The development of efficient noble-metal-free electrocatalysts for biomass upcycling at near-neutral pH remains a significant challenge. In this study, we report on NiOOH-based electrocatalyst-modified electrodes, prepared via a facile anodic pulse-current electrodeposition, demonstrating high performance for the electrocatalytic oxidation of 5-hydroxymethylfurfural ( e -HMFOR). The effects of electrode preparation conditions (e.g., plating solution composition, loading of active species, and anodic pretreatment) and electrolysis conditions (e.g., 5-hydroxymethylfurfural concentration and light irradiation) were systematically investigated through a series of controlled-potential electrolysis (CPEs). In-situ Raman analyses, XPS analyses, and CPEs reveal that the incorporation of cobalt species is critical in facilitating and sustaining the formation of active high-valence nickel species during the anodic pretreatment and e -HMFOR under light illumination. Increasing the active species loading promoted the extent of e -HMFOR, boosting 2,5-furandicarboxylic acid production by upto 20 times. Mechanistic studies confirm that the reaction pathway initiates via alcohol moiety oxidation to form 2,5-diformylfuran as the first intermediate. Under optimal conditions, the developed electrode demonstrated excellent stability, maintaining Faradaic efficiency above 91% in the prolonged electrolysis under both dark and illuminated conditions. These results provide an integrated strategy, combining cobalt incorporation, anodic activation, and light irradiation, for designing nickel-based electrocatalysts for efficient and light-assisted biomass valorization. An integrated strategy, combining cobalt incorporation, anodic activation, and light irradiation, to facilitate high-valence nickel species formation, was developed for designing transition-metal oxyhydroxides for efficient, light-assisted biomass-derived feedstocks upcycling. • An integrated strategy for efficient e-HMFOR at near-neutral pH was proposed. • Co species effectively promote and sustain the formation of high-valence Ni species. • Faradaic efficiency > 91% using a noble-metal-free catalyst was first demonstrated. • e-HMFOR initiates via alcohol moiety oxidation of HMF at developed catalyst.