Electrocatalytic Oxidation of 5‐Hydroxymethylfurfural into the Monomer 2,5‐Furandicarboxylic Acid using Mesostructured Nickel Oxide

Transforming biomass based compounds with renewable electrical energy into products presents a promising approach towards development of a circular economy. Herein, 5-hydroxymethylfurfural (HMF), derivable from cellulose and hemicellulose, is successfully electrochemically converted into 2,5-furandicarboxylic acid (FDCA). The reactions are performed in alkaline aqueous solutions using commercial nickel oxide (NiO) or a mesostructured nickel oxide derived by CMK-1 templating (NiO-CMK-1). Both catalytic activity and the selectivity of FDCA are highly dependent on the catalyst structure. NiO-CMK-1 facilitates multiple times higher FDCA selectivity (>80%) compared with commercial NiO (30%). Electrochemical analyses emphasize a net-current density for NiO of 2 mA cm−2 whereas for NiO-CMK-1 the net-current density increases significantly to above 4 mA cm−2. The exposed material surface and structure of the catalysts are analyzed via nitrogen physisorption and powder X-ray diffraction revealing that both NiO and NiO-CMK-1 possess a face-centered cubic crystal structure but distinctly different exposed surface areas. Since NiO-CMK-1 enables remarkably improved catalytic activity for the oxidation of HMF, a recycling study is conducted with five consecutive catalytic cycles emphasizing the technological potential of this approach.