Carbonate-incorporated cobalt hydroxides for enhanced performance in the electrocatalytic oxidation of5-hydroxymethylfurfural

Electrocatalytic oxidation of biomass-derived 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid offers a sustainable route to high-value chemicals. Anion doping in cobalt-based catalysts can modulate catalytic performance by altering the coordination environment and electronic structure of active sites, thereby affecting surface reconstruction and reaction kinetics. Here, anion-modified cobalt hydroxysalts (Co(OH)_2−x(A^m−)_x/m, A = CO₃, F, and Cl) were synthesized to investigate anion-specific effects on electrooxidation of 5-hydroxymethylfurfural. The carbonate-incorporated nanowire catalyst exhibited outstanding performance, lowering the oxidation potential to 1.33 V at 50 mA·cm⁻² and increasing the active site density by 1.5 times relative to undoped Co(OH)₂. In contrast, F⁻ and Cl⁻ doping led to redox potential shifts and reduced activity. In situ Raman spectroscopy revealed that the catalytic reaction was driven by active CoOOH species generated under anodic polarization. This process was accompanied by carbonate leaching and irreversible phase changes, which contributed to catalyst deactivation. This study provides insights into anion-controlled catalyst design for efficient and durable biomass electrooxidation.