Surface Structure-Dependent Oxidation of 5-Hydroxymethylfurfural on Gold Single-Crystal Electrodes: Insights into Catalytic Activity and Selectivity

The selective electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) holds transformative potential for advancing sustainable, bio-based polymer production. In this study, we unveil the pivotal role of gold single-crystal electrode surface orientation in directing HMF oxidation pathways under alkaline conditions. Using cyclic voltammetry, we systematically evaluated the oxidation behaviour on Au(111), Au(100), Au(110), Au(311), Au(331), and Au(210) surfaces. Our findings reveal that Au(111) and Au(100) surfaces exhibit superior catalytic activity for the complete oxidation to FDCA, while Au(110) promotes the selective formation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). These differences in activity are closely linked to the crystallographic structure, influencing adsorption energies and reaction intermediates. In situ infrared reflection absorption spectroscopy (IRRAS) and attenuated total reflectance (ATR) spectroscopy provided direct molecular insights, identifying distinct vibrational signatures of intermediates and products. This study highlights the critical role of electrode surface structure in tuning reaction efficiency and selectivity, paving the way for more efficient catalytic processes in green chemistry.