Which electrode is better for biomass valorization: Cu(OH)2 or CuO nanowire?

2,5-furandicarboxylic acid (FDCA), one of the key building block for replacing petroleum-derived tereph-thalic acid, is utilized as the source of bioplastics, pharmaceuticals. Herein, free-standing Cu(OH)2 and CuO nanowires as electrode were examined to disclose the effects of crystal structure and chemical formation based on copper oxide in electrocatalytic 5-Hydroxymethylfurfural (HMF) oxidation to FDCA in 0.1 M KOH solution. We introduced on three-dimensional copper foam (CuF) with high porosity as copper source and substrate with high conductivity free-standing Cu(OH)2 and CuO nanowires (NWs) on the substrate by inorganic polymerization and calcination for electrochemical HMF oxidation. This was enabled by square-planar coordination (σx2-y2) of Cu2+ ions in (001) crystal faces of Cu(OH)2 crystal. As a result of stacking with hydrogen bonds, free-standing Cu(OH)2 NWs on the substrate was formed. There was no change in the morphology of the nanowire arrays, but the active sites from a plane area per surface-exposed Cu atoms by transformation of Cu(OH)2 to CuO NWs increased.